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Diets Decoded: The Nuts and Bolts of Nutrition Nursing CE Course

3.5 ANCC Contact Hours

About this course:

This learning activity aims to help nurses and other healthcare professionals have a clearer understanding of the details, risks, and benefits associated with some of the more common dietary plans popular with patients in the US today.

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This learning activity aims to help nurses and other healthcare professionals have a clearer understanding of the details, risks, and benefits associated with some of the more common dietary plans popular with patients in the US today.

After this learning activity, learners will be prepared to:

  • Define the current epidemic of obesity in the US and discuss strategies for weight loss
  • Explore the current research regarding balanced diets such as MyPlate, the Mediterranean diet, the DASH diet, the Mayo Clinic diet, the Diabetic Prevention Program, and Weight Watchers (WW) to help elucidate their basic guidelines and potential risks and benefits
  • Explore the current research regarding extremely low-calorie diets such as Optifast and low-fat diets such as the Ornish diet to help elucidate their basic guidelines and potential risks and benefits
  • Explore the current research regarding low-carbohydrate diets such as the Atkins and ketogenic diets and moderate-carbohydrate diets such as the South Beach, low glycemic index, and Paleo/Whole 30 diets to help elucidate their basic guidelines and potential risks and benefits
  • Explore the current research regarding plant-based and plant-predominant diets and specialty diets to help elucidate their basic guidelines and potential risks and benefits
  • Explore the current research regarding mobile weight management applications for smartphones to help elucidate their basic guidelines and potential risks and benefits

Diets Decoded: The Nuts and Bolts of Nutrition all Nurses Should Know

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), over 70% of the US population is considered overweight, obese, or severely obese. The NIDDK defines overweight as a body mass index (BMI) of 25-29.9, obesity as a BMI more than 30, and severe obesity as a BMI over 40. See Table 1 below for additional BMI details (NIDDK, 2017). 

According to the Centers for Disease Control and Prevention (CDC, 2021d), the prevalence of adult obesity in the US was 42.4% from 2017 to 2018, with roughly 93.3 million adults affected nationwide. The CDC considers several associated conditions obesity-related, including heart disease, stroke, type 2 or non-insulin-dependent diabetes mellitus (NIDDM), and some types of cancer. Obesity is especially prevalent among certain ethnic and age groups. The prevalence of obesity among non-Hispanic Black adults is highest at 49.6%, followed by Hispanic adults (44.8%), non-Hispanic White adults (42.2%), and lowest among Asian adults (17.4%). Middle-aged adults between 40 and 59 years have the highest prevalence of obesity of any adult age group at 44.8%. In addition, individuals without a college degree and those within the middle-income range tend to have higher rates of obesity than those with college degrees or at lower and higher income ranges (CDC, 2021d). 

Childhood obesity is a serious problem in the US. Suffering from obesity during childhood increases the risk of developing health complications later in life. Obesity in children is defined as a BMI at or above the 95th percentile. From 2017 to 2018, childhood obesity affected 19.3% (14.4 million) of children between 2 and 19 years old. The prevalence of obesity was 13.4% among 2- to 5-year-olds, 20.3% among 6- to 11-year-olds, and was highest among 12- to 19-year-olds (21.2%). Childhood obesity is more common among certain ethnic groups. The prevalence of obesity was highest among Hispanic children at 25.6%, followed by non-Hispanic Black children at 24.2%, non-Hispanic White children at 16.1%, and non-Hispanic Asian children at 8.7%. Parental education level and socioeconomic status also affect childhood obesity rates. As the level of education achieved by the parents increased, the rate of obesity among their children decreased. The rate of childhood obesity was highest among children aged 2-19 years old in the middle-income group at 19.9%. The prevalence of obesity among non-Hispanic Black girls was not affected by income (CDC, 2021d). 

Dietary Recommendations

General Guidelines 

The general recommendations from the CDC (2021e) for weight loss and healthy weight maintenance include the MyPlate program. The MyPlate website allows participants to calculate the number of calories needed to achieve or maintain their recommended weight and provides a personalized meal plan based on that number. The food plan is based on an individual’s age, gender, height, weight, and physical activity level. For children ages 6-17 years old, recommendations include at least 60 minutes of moderate to vigorous physical activity per day. Children's physical activity should consist of aerobics, activities that strengthen muscles such as climbing, and bone-strengthening activities such as running and jumping. Recommendations for adults aged 18-64 include a goal of 150 minutes of moderately strenuous physical activity per week and two or more days of muscle-strengthening exercises per week to help achieve or maintain their goal weight and overall health. It is recommended that healthy adults over the age of 65 engage in 150 minutes of moderate activity per week. For this age group, it is recommended that at least two days a week include activities that improve muscle strength and balance (CDC, 2021e). 

According to the CDC (2021e), individuals should not reduce the variety of foods eaten when attempting to lose weight, as restrictive eating can exclude vital nutrients from the overall diet. It is also recommended that individuals drink enough water per day and get adequate sleep, as both can facilitate weight loss (CDC, 2021e). The CDC encourages individuals to contact their healthcare provider (HCP) before starting any diet or weight loss plan. The guidelines emphasize that any weight loss program should offer behavioral treatments and lifestyle counseling (usually multiple one-on-one or group sessions over several months) and address key issues such as sleep and stress management. Weight loss programs should provide ongoing monitoring, feedback, support, and a long-term maintenance plan to prevent rebound weight gain. Weight reduction should be slow and steady with a realistic goal of losing 5% to 10% of overall body weight over 6 months. Before starting a weight loss program, patients should consult with their HCP regarding the approach’s safety, efficacy, and typical results. Patients should be encouraged to research potential costs, the amount of time required for grocery shopping and meal prep, the training or education requirements for the program’s staff, and whether the program has counselors available (NIDDK, 2017). 

While the Mayo Clinic (2020c) has developed its own diet program, which will be reviewed later in this activity, its public website addressing healthy weight loss makes many of the same suggestions discussed above. They also recommend that individuals consider their history with dieting and what has worked or not worked for them, their household budget, and preferences related to specific diet or weight loss programs. It is also important to consider cultural or ethnic food restrictions or guidelines and allergies before choosing a weight loss program (Mayo Clinic, 2020c).  

If a patient is interested in attempting weight loss independently, the CDC (2021e) recommends they first analyze their caloric baseline by keeping a daily log or diary of all intake, in addition to an activity log to monitor their daily exercise. Once this baseline is established, patients should then try replacing high-calorie foods with foods high in fiber and water content to help reduce caloric intake by increasing satiety (i.e., the sensation of feeling full). Other suggestions for reducing caloric intake inc

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  • substituting high-calorie drinks with water
  • decreasing portion sizes
  • utilizing low-fat or fat-free dairy products
  • utilizing water or cooking spray instead of butter or vegetable oils for cooking
  • adding vegetables such as lettuce, tomato, cucumber, and onions to sandwiches instead of additional meat or cheese
  • eating salad or fruit as a side dish instead of potato-based sides such as chips or fries
  • eating clear vegetable-based broth soups in place of cream-based
  • dipping the fork into the salad dressing with each bite of salad instead of pouring the dressing on top of the dish
  • steaming or grilling vegetables instead of frying or sautéing them
  • adding vegetables to pizza instead of high-calorie meats
  • snacking on vegetables, fruit, yogurt, air-popped popcorn, or dry-roasted nuts (CDC, 2021c)

In short, most experts recommend simply eating wholesome foods in sensible combinations. As author Michael Pollan explains, “Eat food. Not too much. Mostly plants” (Bisley, 2019, para. 2). 

Regarding exercise, the typical recommendation is for moderate-intensity exercise most days of the week (see above); however, this has been tested and may not be the ideal suggestion for those looking to lose weight. A study reviewing the evidence behind four different weight-loss techniques (the Paleo diet, juicing/detoxification diets, intermittent fasting [IF], and high-intensity interval training [HIIT]) indicated that the three diets all achieved short-term weight loss by reducing caloric intake. However, only the HIIT training plan improved cardiovascular health and achieved weight loss (Obert et al., 2017). A study completed by Mattioni Maturana and colleagues (2021) analyzed the benefits of high-intensity interval exercise (HIIE), which includes HIIT and sprint interval training (SIT), versus moderate-intensity continuous training (MICT) on physical health indicators and weight loss. MICT is defined as endurance training or moderate-intensity activity performed for a prolonged period. In most studies, HIIT/SIT was defined as periods of reaching >80% of maximum oxygen uptake and >85% of maximum heart rate interspersed with lower-intensity periods to allow for recovery. The results showed that engaging in HIIE was more effective at improving cardiovascular health and cardiorespiratory fitness than MICT, and mortality rates from cardiovascular events were reduced. MICT was more effective at improving long-term glucose metabolism and HbA1c results. There was no difference between HIIE and MICT exercise routines regarding systolic and diastolic blood pressure, body mass, percent body fat, low-density lipoprotein (LDL), triglycerides, total cholesterol, and fasting blood glucose levels (Mattioni Maturana et al., 2021).      

Diet Plans 

The Mediterranean Diet

The Mediterranean diet is ranked by US News & World Report (USNWR, 2022b) as the best overall and easiest diet to follow. It promotes a wholesome diet that is predominantly plant-based, with moderate fat and protein intake shown to provide the same cardiovascular benefits as low-fat and low-carbohydrate diets (Cohen, 2018). The Mediterranean diet is high in vegetables, fruits, nuts, cereals, whole grains, and healthy fats such as olive oil. This diet includes moderate amounts of fish and poultry with a reduced amount of sugar, red meat (limited to only a few times per month), and dairy products. It is low in saturated fats but high in monounsaturated fats, fiber, and antioxidants. Studies evaluating this type of diet have dispelled the common misconception that patients at an increased risk for cardiovascular disease must adhere to a strict low-fat diet. With the Mediterranean diet, the daily amount of fat is 39%–42% of total calories, which is higher than the amount recommended by the Institute of Medicine (IOM) and the US Department of Agriculture (USDA), which is 20%–35% of total daily calories (Harvard T. H. Chan School of Public Health [HTHCSPH], 2018f). Studies have shown it is most effective at reducing the risk of obesity-related diseases such as coronary artery disease (CAD), NIDDM, metabolic syndrome, and cardiovascular mortality. In pregnant women, the Mediterranean diet may reduce the risk of neural tube defects, preterm birth, and fetal growth restriction (D’Innocenzo et al., 2019; HTHCSPH, 2018f). 

Anton and colleagues (2017) found a short-term and two long-term randomized clinical trials showing an average weight loss of 7.2% of body weight at 3 months and between 4.9% and 8.7% at 12 months. A lower-carbohydrate version of the Mediterranean diet was shown in the same review to produce a slightly higher weight loss of 10.3% at 12 months (Anton et al., 2017). The average American diet comprises roughly 55% carbohydrates (between 200 and 350 g/day); in contrast, when following the Mediterranean diet, carbohydrates should account for less than 45% of daily calories (Masood et al., 2021). Some data shows that women who follow this diet have a 25% lower risk of developing cardiovascular disease (HTHCSPH, 2018f). The minimally processed food in the Mediterranean diet and the predominance of plants-based meals are thought to lead to health promotion and disease prevention benefits. Studies have also shown decreased insulin resistance, increased longevity, preserved cognition, reduced blood pressure, and reduced cancer risk related to the Mediterranean diet (Cohen, 2018). A final benefit is the allowance of one glass of red wine for women and two glasses of red wine daily for men. This allowance of daily wine intake may make the Mediterranean diet more attractive to some people. When following the Mediterranean diet, meals should take place in a relaxed, social environment. Regular physical exercise is also a key component. The Mediterranean diet does not emphasize calorie restrictions or set portion sizes; therefore, participants should be encouraged to monitor their daily caloric intake to facilitate any desired weight loss (HTHCSPH, 2018f).

Dietary Approaches to Stop Hypertension (DASH) Diet

The DASH diet was first introduced at a meeting of the American Heart Association (AHA) in 1996 and was published in the New England Journal of Medicine in 1997. It was created as a treatment option for patients with high blood pressure (HTHCSPH, 2018a). The USNWR (2022c) ranked this diet second in Best Diets Overall due to its heart-healthy guidelines but listed the cost and amount of work required to adhere to the diet as cons. The diet is primarily plant-based, including low-fat or fat-free dairy products. The DASH diet incorporates fruits, vegetables, beans, nuts, whole grains, reduced-fat dairy, fish, and poultry while limiting sodium to less than 2,300 milligrams per day (eventually decreasing sodium intake further to less than 1,500 milligrams per day) while avoiding refined sugar, red meat, and saturated and trans fats. This diet is high in potassium, magnesium, calcium, and fiber and moderate in protein intake (USNWR, 2022c). If an individual is eating 2,000 calories a day, the recommended servings are as follows: 

  • 6-8 servings of grains daily,
  • 4-5 servings of fruits daily, 
  • 4-5 servings of vegetables daily, 
  • 2-3 servings of dairy daily, 
  • 2-3 servings of fats/oils daily,
  • fewer than 6 ounces daily of lean meat, poultry, or fish (HTHCSPH, 2018a)

The DASH diet also encourages 4-5 servings per week of nuts and seeds and no more than 5 servings per week of snacks containing refined or added sugar. This diet has been shown to reduce blood pressure, improve kidney function, and reduce uric acid levels in patients prone to gout (HTHCSPH, 2018a). The DASH diet is also reported to reduce the risk of heart failure by as much as 50% and may reduce the risk of depression, stroke, NIDDM, kidney stones, and cancer (Heller, 2021). 

Despite its many documented health benefits and numerous expert endorsements, including the AHA and NIH, there is limited evidence supporting the efficacy of the DASH diet for weight loss. Anton and colleagues (2017) found only a single short-term clinical trial showing evidence that this diet effectively assisted patients with weight loss; however, even this study only found the average weight loss after 4 months to be 0.3% of total body weight. Although the DASH diet was initially created to lower blood pressure and not specifically promote weight loss, many books have been published that combine the original DASH diet plan with the Mediterranean diet. This combination attempts to utilize both the health benefits of the DASH diet and the weight-loss power of the Mediterranean diet. Potential benefits of the combination include a low salt, wholesome, and balanced meal plan with weight loss and health promotion, and disease prevention potential for patients who can afford potentially increased food costs and enjoy planning, prepping, and preparing food (Heller, 2021). 

The Mayo Clinic Diet

HCPs at the Mayo Clinic developed their own weight loss and lifestyle improvement program called Mayo Clinic Diet. The USNWR (2022d) ranked this diet fifth in Best Diets Overall and fourth in Best Diabetes Diets, remarking that it can be expensive and labor-intensive while the diet is flexible and healthy. Dr. Donald Hensrud of the Mayo Clinic authored a second edition of the Mayo Clinic Diet book published in 2017 and outlined the diet plan in detail. Dr. Hensrud also released a diabetes-specific Mayo Clinic Diabetes Diet in 2013, and the second edition of this diet was also published in 2017 (Mayo Clinic Press, 2021). The Mayo Clinic’s website describes the plan as being adaptable, affordable, and capable of helping patients lose between 6 and 10 pounds in the first two weeks (the Lose It! Phase), followed by an additional 1-2 pounds per week after that (the Live It! Phase). The program is designed to last 12 weeks, but the changes developed can purportedly last a lifetime (Mayo Clinic, n.d.). 

The developers of the Mayo Clinic diet emphasize 15 key habits of health. Using their Habit Optimizer, individuals can learn how to swap their unhealthy habits for healthier actions, such as 30 minutes of physical activity every day. Participants are encouraged to increase their intake of fruits, vegetables, and whole grains while reducing their fats and processed sugars intake. After the first 2 weeks, women are instructed to eat between 1,200 and 1,600 calories per day, depending on their current weight, while men are instructed to take in an additional 200 calories per day. Depending on which calorie limit is appropriate, the developers suggest 7-10 daily servings of fruits and vegetables, 4-8 servings of carbohydrates, 3-7 servings of protein and dairy, and 3-5 servings of fats. The website also provides a food pyramid as a tool to help individuals who need a more visual representation of which foods to incorporate into the daily diet. Additional resources are available to patients who subscribe to their monthly diet program, such as tools to track progress and log meals, exercise, body measurements, and weight changes. The program also offers educational content and videos with support from Mayo Clinic physicians, dieticians, and chefs (Mayo Clinic, n.d.).

Diabetes Prevention Program (DPP) 

The National DPP is a partnership between the public and private sectors in an effort to reduce the rates of NIDDM in the US. Developed in 1996 by the CDC and NIH as a clinical trial, the program emphasizes nutritional balance and lifestyle change. The DPP emphasizes eating a plant-based diet combined with lean meats and a reduced amount of processed starches and sugar. It also incorporates exercise into the regimen. Since the clinical trial did show a reduction of NIDDM in 58% of high-risk adults who followed the program with an average weight loss of 5%–7% of total body weight, the plan was recognized by Congress as the National DPP in 2010 (CDC, 2021b).  

In its current version, the DPP incorporates goal-based behavioral-intervention techniques with a reduced-calorie and reduced-fat diet, along with regular exercise to induce weight loss. The lifestyle change program is one year in length. It consists of one-hour weekly meetings for the first 6 months followed by monthly meetings for another 6 months to educate and support participants regarding diet, exercise, and stress management. Medicare Part B and some employers and private insurers offer coverage for the program; however, if a patient is paying out of pocket, prices may vary depending on location and administrator. The daily caloric intake needed to maintain the current weight is calculated. Then 500-1,000 calories are deducted from that number to initiate a caloric deficit that leads to sustained, safe weight loss. No more than 25% of daily calories should be derived from fat intake. The recommended daily intake varies from 1,200 calories and 33 g of fat for an individual weighing 120-170 pounds up to 2,000 calories and 55 g of fat for an individual weighing over 250 pounds. Physical activity is incorporated into the DPP, and participants are encouraged to increase their physical activity to 150 minutes per week. Patients are given a pocket guide to help them keep detailed food and activity logs to promote accountability (CDC, 2021a). 

Weight Watchers (WW)

Jean Nidetch developed the WW diet. In 1961 she started the WW company based on her diet plan. As one of the country’s longest-lasting commercial diet programs, WW is a combination diet, physical activity, and behavioral modification plan. It is based on a personalized point system, where foods are assigned point values based on their caloric and nutritional value. Individuals are instructed to monitor and limit their daily point intake to simplify limiting their caloric intake. The point system is combined with weekly accountability sessions (weigh-ins) and educational/group support meetings (Barnett, 2018). WW was ranked as the fifth Best Diet Overall by USNWR (2022j), first in Best Weight-Loss Diets among commercial plans, and third in Easiest Diets. Their expert panel indicated that participants liked the flexibility of having no off-limit foods but commented that the program could be expensive. The enrollment fee is $20 to get started, followed by $3.22 to $12.69 weekly depending on the level of support selected. Although there are costs to the program, studies have shown that the cost savings at the grocery store were more significant than the membership fees (USNWR, 2022j).

The development of an online version and mobile app has allowed participants to participate remotely. The point system encourages eating fewer calories and less saturated fat and refined sugar while encouraging eating more fruits, vegetables, and lean protein by assigning a zero-point value to over 200 of the healthiest food options. Each individual’s daily point allowance is personalized based on their age, height, weight, and sex, and therefore no two programs are the same. The program also encourages increased physical activity. A mobile app, dining out guide, and several “Nearly No Cook” recipes that incorporate grocery store staples and prepared ingredients make the program user-friendly, especially for individuals who cannot commit to or maintain the intense prep work that some other diet plans require. The mobile app allows users to search an online database for items or scan their barcodes to determine point values. This calculation system eliminates the need for the individual to try and guess the point value of certain items, effectively increasing the program's ease of use (USNWR, 2022j). 

WW has been extensively studied. One study reviewing the weight loss of individuals participating in WW versus a control group found that the average weight loss for those following WW was 2.6% more than the control group over 12 months. The WW plan also showed a short-term reduction in blood pressure (although the long-term reduction was inconsistent). Studies showed no significant lipid or glucose control changes. More research is needed to determine longer-term benefits (12-24 months), the ability of participants to maintain long-term weight loss, and the effectiveness of WW for individuals with a BMI greater than 42 (Barnett, 2018).  

Very-Low-Calorie Diets (VLCDs)

Typically, VLCDs limit consumption to 800 kcal per day. Due to the restrictive nature of these types of diets, they are not recommended for long-term routine weight management. It is also recommended that individuals interested in these diet plans consult with their HCP for monitoring. VLCDs are contraindicated in pregnant women and patients with type 1 diabetes, kidney failure, or cardiac arrhythmias. Studies have shown that these diets effectively reduce weight and provide more long-term weight loss than participating in behavioral modification programs alone. It has also been found that VLCDs can lead to diabetes remission in patients who have been obese for over 2 years (Kim, 2021). These diets often consist of total meal replacement (TMR) foods, such as prepackaged shakes or bars. While TMR eliminates or significantly limits an individual’s meal choices, it allows for more controlled portions and greater satiety with fewer calories (Ard et al., 2019).


OptiFast is a commercial weight-loss program by the Nestle corporation (who also funded the primary research study cited in their evidence) for patients with a BMI of 30-55. This medically managed, 12- to 16-week TMR program advertises an average 30-pound weight loss after 6 months of participation and 25 pounds after 12 months. For individuals with a BMI of 30-49.9, all meals are replaced with TMR foods. The meal replacements range from 5-6 small meals daily (depending on where current BMI falls in the range of 30-49.9) for a total caloric intake of 800-960 calories per day. Individuals with a BMI over 50 are allowed one small food-based meal of 200-250 calories in addition to the 5-6 meal replacements per day. The meal replacements provide 40% of total calories from carbohydrates, 40% from protein, and 20% from fat. After the active weight loss phase, there is a 4- to 6-week period of transitioning back to food-based meals, followed by a maintenance phase that lasts through 52 weeks (OptiFast, n.d.). 

In their primary efficacy and safety study, 135 patients underwent the OptiFast plan. In comparison, 138 patients participated in a roughly equivalent low-calorie (500-750 calories below estimated energy expenditure), low-fat (25%–30%), modified DPP food-based program. Both groups attended weekly behavioral group sessions during the initial 26 weeks. The OptiFast group completed metabolic profiles periodically throughout the first 16 weeks of the program. The OptiFast group had 11 medical visits throughout the initial 26 weeks of the study and 4 additional medical visits between weeks 27 and 52. The food-based group had just 4 medical visits over the 52-week study. During the initial 26 weeks, participants in the OptiFast group had 16 individual counseling sessions with trained interventionists, followed by 11 sessions during weeks 27-52. The food-based group had 7 counseling sessions during weeks 1-26 and 5 during weeks 27-52. Follow-up continued for 52 weeks, at which point the OptiFast group had lost 10.5% of their body weight while the food-based group had an average weight loss of 5.5% (Ard et al., 2019). 

The Optifast program boasts reductions in participants’ blood glucose, blood pressure, and total cholesterol levels. Advantages can include the simplicity of avoiding grocery shopping and preparing food, and avoiding the calculations involved in most diets to reduce caloric or carbohydrate intake. The downside is the obvious lack of choices and the questionable practice of not eating real, fresh food for an extended period (Optifast, n.d.).


Another type of VLCD is the Optavia diet. This diet was ranked second by USNWR (2022g) in Best Fast Weight-Loss diets but number 27 in Best Diets Overall. This diet restricts intake to 800-1,000 calories per day and relies on meal replacements similar to the Optifast diet. The Optavia diet requires that participants eat a mix of pre-purchased meals called “fuelings” and “lean and green” meals, which the participant must prepare at home. The fuelings include bars, shakes, cereal, pudding, pasta, and soup purchased by the participant and sent through the mail. The lean and green meals include:

  • 5-7 ounces of lean protein such as fish, chicken, egg whites, turkey, or soy
  • 3 servings of non-starchy vegetables like lettuce, greens, celery, or cucumbers
  • up to 2 servings of healthy fats, including olive oil, olives, or avocado (USNWR, 2022g)

The Optavia diet also encourages participants to complete 30 minutes of moderate-intensity exercise per day, which can be risky when coupled with the restrictive calorie intake of the meal plan. The average weight loss experienced by participants is 12 lbs. over 12 weeks. Once an individual’s goal weight is achieved, they enter a 6-week transition period where intake slowly increases to 1,550 calories per day. After the 6-week transition period, participants are encouraged to start Optavia’s Optimal Health 3&3 plan, which mixes three lean and green meals with three prepacked fuelings (Shoemaker & McGrance, 2022). 

Downfalls of the diet include its high price, limited food options, and reliance on processed meals. The diet can be extremely pricey, with costs averaging $20 per day for prepackaged meals. This amount does not include the additional cost of purchasing the ingredients for the lean and green meals from the grocery store. The average participant will consume over 150 prepackaged meals each month, which is concerning since these meals are highly processed. One-on-one coaching is available with this diet plan; however, the coaches are often previous Optavia users that have taken a training course but have no formal nutritional training. Therefore, the coaches are not qualified to give any dietary advice, and all concerns should be addressed with an HCP. Although this diet has been shown effective for short-term weight loss, there is a lack of research on its long-term effectiveness. There have also been concerns raised by registered dieticians and nutritionists that the company operates using a multi-level marketing business model due to the reliance on direct sales, with the coaches making a commission off the products that each participant purchases (Shoemaker & McGrance, 2022). 

The Low-Fat (Ornish) Diet

A physician originally developed the Ornish diet. Dr. Dean Ornish in California founded the Preventive Medicine Institute to help people lose weight, gain health, feel better, and live longer. The Ornish diet was ranked by USNWR (2022b) as the best diet for heart health; however, their expert panel found that it could be expensive and difficult to maintain. The program encourages a diet rich in plants, fiber, and some complex carbohydrates. It significantly limits fats (<10% of daily caloric intake), refined carbohydrates, and animal protein. The Ornish approach also incorporates the importance of stress management, exercise, and building emotional health through interpersonal relationships. It consists of 5 food categories that help participants fill their grocery carts with the healthiest food choices. The plan limits cholesterol, oils, excessive caffeine, and nearly all animal products, except for egg whites and a cup of skim milk or nonfat yogurt daily. The diet also allows participants to consume 2 ounces of alcohol daily (USNWR, 2022b). 

Experts applaud the diet for its diverse and nutrient-rich nature. Substantial evidence in a landmark study from the 1990s showed its efficacy in shrinking atherosclerotic plaques and reducing the risk of recurrent myocardial infarction in high-risk adult patients. A follow-up study in 2014 of 198 patients with significant CAD showed that 99.4% of patients that adhered to a low-fat diet over 4 years experienced no major cardiac events, stroke, or death (Esselstyn, 2017). Anton and colleagues (2017) compared the Ornish diet to six others in a systematic review and found two short-term and long-term trials. These trials involved fewer than 400 participants and resulted in a 2.9% – 3.5% weight loss at 6 months and a 2.6% – 3.2% weight loss at 12 months (Anton et al., 2017). 

Low-Carbohydrate Diets

The Atkins Diet

The Atkins diet was developed by Dr. Robert Atkins (a cardiologist) in the 1960s. It was ranked 34th by USNWR (2022b) in Best Diets Overall (out of 40) but tied for first place in Best Fast Weight-Loss diets. The panel noted the abundance of fatty foods that could be eaten “guilt-free” and quick drop in weight but found the carbohydrate rules highly restrictive and voiced concerns about significant health issues associated with a diet so high in fat. The Atkins diet launched the low-carbohydrate diet trend, and it originally stressed a very low level of carbohydrate intake and unlimited intake of protein and fats. The diet occurs in 4 phases. During Phase 1, which is called induction, participants are only allowed 20 g of net carbohydrates (fiber) daily for 2 weeks; 12-15 of these need to be derived from what the founder of the diet calls “foundation vegetables,” such as arugula, cherry tomatoes, and brussel sprouts (USNWR, 2022a). During Phase 2, which is called balancing, participants slowly add small amounts of berries, nuts, and seeds back into their diet. They continue Phase 2 until they are 10 pounds from reaching their goal weight. During Phase 3, called pre-maintenance, participants are instructed to add roughly 10 g of carbohydrates per week back into their diet through starchy vegetables, fruits, and whole grains until they reach their goal weight. Once at their desired weight, participants begin Phase 4, or lifetime maintenance. This phase involves balancing carbohydrate intake with long-term weight management (Mayo Clinic, 2020b). 

One systematic review found that carbohydrate restriction consistently led to reduced blood glucose levels independent of weight loss results. This reduction in blood glucose levels resulted in patients requiring less glucose-controlling medications such as insulin. This study also determined that the decrease in blood glucose, weight, and lipid levels reduced the cardiovascular risk of a patient with NIDDM. Another systematic review of randomized controlled trials of low-carbohydrate versus low-fat diets showed that a low-carbohydrate, high-protein diet was more effective at reducing weight and cardiovascular risk at 6-months (Matarese & Harvin, 2018). Anton and colleagues (2017) found ten trials regarding the use of the Atkins plan in their systematic review ranging from 6-24 months in duration. Nine of the ten trials showed clinically meaningful weight loss in the short-term; of the eight long-term trials, 6 showed clinically meaningful weight loss at 1 and 2 years. These results were significantly better than any of the other six diet plans the team reviewed, including the DASH diet, glycemic-index diet, Mediterranean diet, Ornish diet, Paleolithic diet, and zone diet (Anton et al., 2017). 

Experts warn that carbohydrate reduction in the absence of calorie reduction may contribute to weight gain and cause adverse metabolic effects. They stress that newer versions of the diet plan that have been published recently should limit fats and protein and encourage the selective use of healthier carbohydrates such as vegetables and beans. They also raise concerns about the environmental and ethical issues surrounding a heavily meat-focused, animal-based diet. The response to these concerns has been the development of the eco-Atkins diet, a similarly high-protein plan that is plant-based. A randomized control trial revealed that this low-carbohydrate diet composed of higher quality unsaturated fat from nuts and plant protein further reduced LDL cholesterol (Gonzalez et al., 2020; Matarese & Harvin, 2018; Sievenpiper, 2020). The Atkins plan should not be recommended to patients with severe kidney disease or pregnant or breastfeeding women. Common side effects during the early phases include headaches, dizziness, weakness, fatigue, constipation, and an increased risk for ketosis. Patients on oral or subcutaneous diabetic medications or diuretics should consult their HCP regarding medication adjustments before initiating a low-carbohydrate diet such as the Atkins diet (Mayo Clinic, 2020b).

The Ketogenic (Keto) Diet

The keto diet is a low-carbohydrate, high-fat, moderate-protein diet initially developed and used to manage seizure disorders. Adhering to the keto diet has been shown to therapeutically reduce the frequency of seizures by 50% in adults without using anti-seizure medications (Reddel et al., 2019). The keto diet has also been used therapeutically for other neurological conditions such as Alzheimer’s disease and patients diagnosed with diabetes, cancer, and polycystic ovarian syndrome. The name is derived from ketogenesis, a metabolic process in which the liver produces ketone bodies from fat stores after 3-4 days of minimal glucose ingestion (HTHCSPH, 2018d). The diet encourages about 55%–60% of daily calories from fat, 30%–35% from protein (or 1-1.5 g per pound of body weight), and 5%–10% from carbohydrates (Masood et al., 2021). Some versions of the plan allow up to 80% of daily calories from fat. Foods eliminated while following the diet include beans, legumes, and most fruits. Participants are encouraged to eat all fats, fish, some berries, some cheese, leafy green vegetables, cauliflower, broccoli, brussel sprouts, asparagus, bell peppers, onions, garlic, mushrooms, cucumber, celery, summer squash, nuts, and seeds (HTHCSPH, 2018d). Participants are limited to between 20 and 50 g of carbohydrates daily and encouraged to limit protein intake to moderate levels to facilitate the process of ketosis. A ratio of 1 g of carbohydrates for every 2 g of protein and 4 g of fat is generally recommended (Harvard Health Publishing, 2020). 

Due to the reduced insulin levels found in the body during ketogenesis, the diet reduces the storage of both fat and glucose. Short-term studies have thus far shown that the keto diet improves glucose control and helps reduce weight, improve blood pressure, and decrease triglycerides, but long-term studies are lacking. The diet is deemed safe to continue for 6-12 months in otherwise healthy patients. However, renal function should be monitored while following this diet plan, and patients should be instructed to resume more normal diet habits after that time gradually. Patients should be thoroughly educated on the risks of the keto diet. In the short term, patients may experience headaches, nausea/vomiting, fatigue, dizziness, and insomnia (called the “keto flu”) that may last for a few days to weeks. Like the Atkins diet described above, diabetic and diuretic medications should be reviewed before starting the Keto diet. Due to the increased stress on the body—specifically the liver—the keto diet should not be recommended for patients with a previous history of pancreatitis, liver failure, or disorders of fat metabolism (primary carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine translocase deficiency), porphyria, or pyruvate kinase deficiency. There may also be an associated increase in LDL levels with the keto diet (Masood et al., 2021). Experts also warn that any diet high in saturated fats, as the keto diet most assuredly is, increases an individual's risk of heart disease (Harvard Health Publishing, 2020). 

The keto diet may also lead to nutritional deficiencies in selenium, magnesium, phosphorus, vitamin B, and vitamin C (Harvard Health Publishing, 2020). The Keto diet may also increase uric acid levels and elevate an individual’s risk of developing kidney stones, gout, and osteoporosis (HTHCSPH, 2018d). Due to these risks and the lack of food variety, the keto diet is not recommended for pregnant women. Studies have also shown that participants eating a ketogenic diet have an increase in healthy gut bacteria but an overall decrease in bacterial diversity in their digestive tract. This lack of diversity could negatively impact the essential functions of the human gut microbiota (Reddel et al., 2019). A strict keto diet also carries an associated risk of ketoacidosis, a condition in which the body’s insulin does not adequately control the number of ketone bodies circulating, leading to metabolic acidosis, which requires immediate medical treatment (HTHCSPH, 2018d). In addition, significant concerns exist regarding the environmental impacts and ethical issues surrounding a heavily animal-based diet (Gonzalez et al., 2020). 

Moderate-Carbohydrate Diets

The South Beach Diet

Cardiologist Dr. Arthur Agatston originally developed the South Beach diet plan in 2003. It is named after the Miami, Florida area known as South Beach. Originally developed to help participants choose good carbohydrates and good fats and avoid bad carbohydrates and bad fats, the USNWR (2022b) ranked this diet tied for 20th in Best Diets Overall and seventh among commercial diet plans. Short-term studies show the plan may reduce weight and total cholesterol (Mayo Clinic, 2020a). This diet encourages participants to eat six small meals comprised of lean meats and lots of vegetables, and some fruits, low-fat dairy, monounsaturated fats, and complex and low-glycemic-index (GI) carbohydrates per day. Participants are encouraged to avoid simple carbohydrates, including sugar, but are allowed to consume two servings of lower-carbohydrate alcohol per week, such as red wine. In addition, the plan encourages 30 minutes of exercise daily during the acute weight loss phase and 60 minutes during the maintenance phase (USNWR, 2022h). 

The original South Beach diet plan consists of 3 phases. Phase 1, known as the body reboot, lasts 2 weeks and cuts out almost all carbohydrates from the diet to eliminate cravings for sugary, sweet, and starchy foods. Participants cannot consume bread, pasta, fruit, rice, or alcohol during this phase. Phase 2 involves long-term weight loss. During this phase, whole grains, brown rice, and some previously avoided vegetables and fruits are gradually reintroduced until the patient reaches their goal weight. Phase 3, known as the maintenance phase, starts when the participant reaches their goal weight. This phase encourages the balancing of carbohydrate intake and weight for life. In this phase, an individual can get as many as 28% (140 g) of their daily caloric intake from carbohydrates. The latest version of the South Beach Diet now includes a mail-order meal delivery service. The current plan reduces Phase 1 eating to a week, followed by 3 weeks of Phase 2 meals delivered to clients’ doors. The company advertises an 8- to 13-pound weight loss, mainly from the abdominal area, in the first week, followed by 1-2 pounds a week after this (Mayo Clinic, 2020a). The meal plan does have a cost associated with the meals that must be purchased. Prices for items range from $2.49 to $6.99. Although the meal delivery service can be more convenient, followers of the diet plan will still have to pay more for groceries to meet the requirements. At this time, the company is revamping its meal plans and food selections, so items can only be ordered a la carte. Participants also have access to cookbooks, grocery shopping guides, an official weight loss blog, private Facebook support groups, and support via the South Beach mobile app. The mobile app offers meal-, weight-, and goal-tracking features and additional counselor support 7 days per week (USNWR, 2022h). As with other diets, significant concerns exist regarding environmental and ethical issues related to a meat-heavy, animal-based diet (Gonzalez et al., 2020).

Glycemic Index (GI) Diet

The GI diet limits carbohydrate intake based on their overall effect on blood glucose levels. Some carbohydrates create an immediate spike in blood glucose, while others provoke an increase that is less intense and slower. The GI diet rating system ranks each food’s effect on blood glucose compared to 50 g of pure glucose (Kim, 2021). This diet may also be termed the Slow Carb diet, and the concept of GI rating is also incorporated into the Zone diet and the SugarBusters diet. The GI diet limits all fruits and some vegetables, and any processed starches and sugars. It is high-fiber and often plant-based rather than high-protein (Mayo Clinic, 2020d). 

Studies have shown that the GI diet offers benefits in managing NIDDM, reducing insulin resistance, and decreasing body weight (Kim, 2021). Each food is assigned a score from the GI database at Sydney University GI Research Services. A food with a low score (1-55) has less of an effect on blood glucose than a food with a high score (70+). The issue with this scoring system is that the GI score ignores the serving size. In addition, the list contains only foods that have been studied and is therefore not an exhaustive, comprehensive list. Not determining the score of a certain food can create confusion and frustration for individuals attempting to adhere to this diet. For these reasons, nutritionists, dieticians, and other healthcare professionals developed the concept of glycemic load (GL), which calculates the GI in a standard serving size of a particular food. Low-GL (1-10) foods include leafy green vegetables, most fruit, raw carrots, kidney beans, bran cereals, and chickpeas. Medium-GL (11-19) food options include corn, bananas, pineapple, raisins, oat cereals, and multigrain, oat bran, or rye bread. High-GL (20+) foods include white rice, white bread, and potatoes. Critics of this system note that neither GI nor GL consider how foods are prepared or processed, what foods are eaten in combination, or their overall nutritional value (Mayo Clinic, 2020d). This diet plan is also incomplete, as there are no recommendations for the daily intake of fats, protein, and fiber (Kim, 2021). Studies of diets based on GI or GL have mixed results but suggest that GL or GI diets may lead to weight loss and a reduction in total cholesterol and LDL levels (Mayo Clinic, 2020d). 


The paleolithic (Paleo) diet is a pattern of eating that attempts to mimic the nutritional pattern attributed to humans during the Paleolithic era over 2 million years ago. This diet is also known as the hunter-gatherer, caveman, or Stone-Age diet (Kim, 2021). There are multiple sources of information about what eating like a paleolithic human means and how the diet should be followed, which makes following this diet plan frustrating. Even scientific experts disagree about what humans consumed during the Paleolithic era and whether that diet can even be replicated in the present day. The general premise is to avoid processed foods and increase daily intake of vegetables, fruits, nuts, seeds, and lean meats. No dairy products or grains are allowed on the paleo diet, and fat intake should be limited to between 25% and 40% of daily caloric intake. Most plans agree that protein and carbohydrates should each account for about 30% of daily calories, but some versions advocate for up to 50% of daily calories from plants and high-fiber carbohydrates. Most paleo plans encourage the purchasing of grass-fed beef, wild-caught salmon, and organic, pasture-raised (or free-range) eggs for protein and encourage the use of olive oil for a healthy source of monounsaturated fats. These plans limit both salt and sugar and do not allow those following the diet plan to consume beans, legumes, alcohol, coffee, or any processed foods. Complex carbohydrates such as sweet potatoes and cassava may be eaten in moderation (HTHCSPH, 2018e). 

Evidence for this type of diet is relatively limited. Short-term studies show a reduction in weight, blood pressure, cholesterol, and waist circumference, along with an increase in insulin sensitivity (HTHCSPH, 2018e). Anton and colleagues (2017) found only one short-term and one long-term clinical trial that showed an average weight loss of 9% in paleo dieters at 6 months and 10.6% at 12 months. Compared with the Nordic diet (see below) in a large, randomized trial, paleo dieters lost significantly more fat mass at 6 months but not at 24 months. Critics point to high grocery costs, high-maintenance meal planning, and potential ethical and environmental concerns regarding a diet consisting of primarily animal products as drawbacks to this diet. Some researchers also argue that the caloric output of a Paleolithic human differs dramatically from modern humans, making the entire premise of the diet invalid. Patients should be warned regarding potential nutritional deficiencies in calcium, vitamin D, and vitamin B that may result from any moderate or prolonged following of this diet (HTHCSPH, 2018e).

Whole30 is a lifestyle plan premised on the paleo diet. If followed precisely, it purports to eliminate cravings, rebalance hormones, cure digestive issues, improve medical conditions, and increase energy and immunity. The plan consists of 30 days of eliminating foods that are common allergens or “pro-inflammatory” from the diet, such as sugar, dairy products, grains, alcohol, and legumes. The intention is to avoid the hassle of counting calories and encourage dieters to pay attention to food origin and ingredients. Critics point to the plan’s high grocery costs, high-maintenance food planning, and lengthy preparation. This short-term plan is only intended to be followed for 30 days (which may reduce many of the risks mentioned above). Participants are instructed to individually reintroduce foods slowly back into the diet to assess the body’s reaction to them. This helps participants determine if the symptoms experienced are food-related and, if so, which foods, in particular, are causing problems (Cleveland Clinic, 2018).

Plant-Based Diets

Vegetarian/Pescatarian Diet

Vegetarian diets are typically plant-based, naturally lower in fat and higher in fiber, and may or may not include eggs and/or dairy products. A vegetarian diet that includes fish and seafood products is called pescatarian. There is extensive population-based evidence for the diet’s general health promotion and disease prevention results, such as reduced weight, a decreased risk for cardiac events and cancer, and overall reduced mortality. In addition, these diets address many concerns regarding the environmental and ethical issues of sustaining an animal-based diet (Gonzalez et al., 2020; Wozniak et al., 2020). Studies have also linked plant-based diets to improved lipid profiles, and a reduced risk of NIDDM yet found increased homocysteine levels (a cardiovascular risk factor) and reduced bone mineral density (Sebastiani et al., 2019). Vegetarians should be encouraged to monitor their daily folic acid (vitamin B9) intake to ensure it does not go above 1,000 mcg/day. High levels of folic acid can cause symptoms such as nausea, anorexia (loss of appetite), confusion, irritability, and sleep disturbance, and mask the symptoms of vitamin B12 deficiency (HTHCSPH, n.d.).  

There is a concern regarding some nutritional deficiencies, such as vitamin B12, for strict vegetarians. Vitamin B12 is a water-soluble vitamin crucial in red blood cell formation, neurological function, and DNA synthesis. Fortified foods (e.g., meat analogs, cereals, nutritional yeast, protein bars, soy or rice milk) and/or supplements should be recommended to maintain adequate B12 levels. All vegetarians should also undergo periodic screenings for B12 deficiency. A healthy B12 level is between 170 and 250 pg/mL. The recommended daily allowance of B12 is between 0.4 and 1.8 mcg for children and adolescents and 2.4 mcg for adults. Pregnant and breastfeeding women need 2.6-2.8 mcg daily. Only about 1% of oral B12 supplements are absorbed. Vegetarian adults should supplement with 25 mcg at least three times per week. Signs and symptoms of low B12 levels include fatigue, poor balance, memory loss, pallor, shortness of breath, extremity paresthesia, depression, confusion, weakness, constipation, diminished appetite, weight loss, or a sore mouth/tongue (Palmer, 2018). Vitamin B12 deficiency is common in individuals following a plant-based diet, and a long-term deficiency can result in irreversible damage to both the brain and nervous system (HTHCSPH, n.d.).

Other deficiencies that can arise with plant-based diets include protein, iron, zinc, calcium, vitamin D, iodine, and omega-3 fatty acids. These deficiencies should be addressed if detected. Daily supplements may be needed (Sebastiani et al., 2019). Protein can be found in nut-based butters and beans. Calcium and vitamin D are abundant in dark leafy greens, soybean products, and some forms of dairy; iron can be found in fortified breads and cereals, as well as beans, lentils, raisins, and blackstrap molasses. Fish is a plentiful source of omega-3 fatty acids, and fortified eggs can also be used. Vegetarian women who are pregnant or breastfeeding should be encouraged to eat about 1.1 g/kg/day of protein, 4-50 mcg/day of B12 (although some nutritionists advise up to 250 mcg/day), 600 mcg/day of vitamin D, 220 mcg/day of iodine, and 1500 mg/day of calcium (Sebastiani et al., 2019). 

Flexitarian Diet

USNWR (2022b) ranked the flexitarian diet tied second in Best Diets Overall and second in Best Plant-Based Diets. The name combines “flexible” and “vegetarian.” Registered dietitian Dawn Jackson Blatner published a book in 2009 explaining how many of the benefits of a plant-based diet could be achieved without strict avoidance of all meat all the time (Cleveland Clinic, 2021a; USNWR, 2022i). The plan is based on Blatner’s five food groups: “new meat” (beans, peas, eggs), fruits and vegetables, whole grains, dairy, and sugar and spice. The plan suggests 300 calories at breakfast, 400 calories at lunch, 500 calories at dinner, and two snacks of 150 calories each daily. Daily calorie intake can be increased or decreased based on an individual’s activity level, height, and weight. Blatner also focuses on emotional health, flexibility, and the pursuit of gradual progress, not perfection. She allows “cheating” by eating meat sparingly when cravings hit (USNWR, 2022i). 

There are three stages of transitioning to the flexitarian diet and decreasing meat consumption. The first stage occurs when an individual decides to start the flexitarian diet. During this stage, participants eliminate meat from their diet for at least 2 days per week and limit meat intake to 28 ounces or fewer for the rest of the week. Stage 2 begins once the individual becomes accustomed to eating less meat. Participants are encouraged to eat a completely vegetarian diet 3-4 days per week during this stage. Meat intake should be limited to 18 ounces on the other days of the week. When an individual is ready, they can start stage 3. During this stage, individuals follow a vegetarian diet 5-7 days per week. If they consume meat during the week, it should be limited to no more than 9 ounces total. When an individual does decide to eat meat, options include wild-caught fish or organic, free-range, grass-fed beef, chicken, or turkey. Participants are also encouraged to eat leaner cuts of meat to minimize fat intake (Cleveland Clinic, 2021a). The plan encourages at least 30 minutes of moderate exercise 5 days per week or 20 minutes of intense exercise 3 days per week (USNWR, 2022i). 

Experts point to the plan’s flexible nature and plentiful recipes on Blatner’s website and in her book but warn that the plan can be labor-intensive and difficult for people who do not enjoy fruits and vegetables. The plan claims to help people lose weight; reduce the risk of heart disease, NIDDM, and cancer; and increase longevity (USNWR, 2022i). Although there are many benefits to following this diet plan, it is not recommended for everyone. Due to the decreased consumption of meat products, poorly planned or unsupplemented diets can risk deficiencies of vitamin B12, zinc, and calcium. This diet is also considered more environmentally friendly due to the reduced meat consumption and carbon footprint (Cleveland Clinic, 2021a). 

Vegan Diet

A vegan or whole-food plant-based (WFPB) diet avoids all animal products. Karlsen and colleagues (2019) found that vegan diets contain 180% more vegetables, 460% more legumes, 100% more whole fruits, 132% more whole grains, and 74% less refined grains than an average diet based on the MyPlate standards. A WFPB diet specifically limits processed foods and refined sugars, fats, and salts and eliminates animal products. While vegan diets are typically higher in carbohydrates than an average American diet (73% vs. 45%–65%), it is typically lower in sugar. The Healthy Eating Index 2015 gave vegan/WFPB diets an 88/100 (Karlsen et al., 2019). Many of the nutritional deficiencies seen in vegetarians can be worsened in vegans if careful consideration is not taken for nutritional balance and supplementation (Palmer, 2018; Sebastiani, 2019). Palmer (2018), a registered dietitian, recommends all vegans supplement with 250 mcg of vitamin B12 daily. 

Epidemiological studies indicate that, compared to the general population, individuals who follow a vegan diet have a lower BMI, lower cardiometabolic risk factors such as blood pressure, LDL, and lower rates of NIDDM, cancer, and heart disease (Krupa Das et al., 2018). Kahleova and colleagues (2019) found that when people transitioned to a vegan diet, their average fat intake dropped from 36.1% to 17.5% of daily calories. This reduction in saturated and trans fats, combined with a relative increase in the percentage of healthy polyunsaturated fats, led to a reduction in fat mass and insulin resistance and enhanced insulin sensitivity. Study participants had an average weight loss of 6.5 kg over the 16-week course of the study, with a 4.3 kg reduction in fat mass (Kahleova et al., 2019). 

Nordic Diet

The Nordic (or Scandinavian) diet is considered regional to Denmark, Sweden, Finland, Iceland, and Norway. The plan was developed at the University of Copenhagen and resembles the Mediterranean diet. One of the significant differences is the type of oil used in cooking. The Nordic diet uses canola oil instead of the extra-virgin olive oil used in the Mediterranean diet (Cleveland Clinic, 2021b). USNWR (2022f) ranked the Nordic diet tied for 10th in Best Diets Overall and tied for fifth in Best Diets for Healthy Eating. This ranking is due to its ability to help patients lose weight, reduce inflammation, and reduce NIDDM risk. Since the diet focuses on whole foods and increased fresh fruits and vegetables, potential benefits can include reduced inflammation, lowered cholesterol, and lowered blood pressure (Cleveland Clinic, 2021b). While the Nordic diet does not avoid all animal products, the plan advocates for protein sources predominantly sourced from seas and lakes. One resource, The Nordic Way, includes a 4-week eating plan (USNWR, 2022f). 

When following the diet, individuals should only obtain about 15% of their daily calories from protein, 25% to 30% from fat, and 55% to 60% from carbohydrates (HTHCSPH, 2018e). When meat is eaten in limited quantities, high-quality meat from local wild landscapes should be chosen. The diet is based predominantly on eating organic, local, seasonal fruits and vegetables and whole grains prepared at home in a social, relaxed environment with family and friends. It emphasizes low GI/GL carbohydrates in at least a 2:1 ratio with proteins. Although enthusiasts claim the approach is healthy, lower in waste, and more environmentally friendly, critics point out that eating in this manner can be expensive, time-consuming, and not always practical due to the effort needed to find environmentally friendly, local food sources. It is also difficult to find authentically Nordic cookbooks and recipes written in English (USNWR, 2022f).

Specialty Diets

Gluten-Free (GF) Diet

A GF diet excludes wheat, rye, barley, and hybrid grains such as Khorasan wheat and triticale. Originally developed to treat celiac disease, a condition of gluten intolerance that affects up to 2% of Americans, this diet has gained more popularity in recent years. Up to 6% of Americans have gluten sensitivity. Gastric symptoms are not as severe as celiac disease but occur when moderate or large quantities of gluten are eaten. Despite these low numbers, up to a third of surveyed Americans report eating a reduced or completely GF diet. Gluten appears in soy sauce and malt vinegar, maltodextrin, wheat starch, bread, pasta, cereals, and processed snacks. The diet concept is to replace these foods with increased amounts of fruits, vegetables, and grains like brown rice, quinoa, and millet. One issue that has started to develop is the reliance on GF processed snack foods. Individuals who substitute a serving of wheat crackers with GF crackers (predominantly made of rice flour) will not experience a caloric or significant dietary difference unless they are part of the 7%–8% of Americans with a true gluten sensitivity or intolerance (HTHCSPH, 2018b). 

Evidence supporting a GF diet for weight loss is lacking. It can lead to weight gain due to a reduction in dietary fiber and an increase in portion sizes due to the mistaken assumption that GF foods are healthier than non-GF foods. Processed GF replacement products are also typically more expensive than their traditional counterparts. Patients should be cautioned about the potential for nutritional deficiencies in vitamin B, iron, and calcium and the potential for an increase in cardiovascular risk with a reduction in dietary fiber (HTHCSPH, 2018b). Studies of bacterial flora indicate that a GF diet reduces healthy bacteria such as lactobacillus and enterococcus and increases Bacteroides, staphylococcus, and Salmonella. Individuals on a GF diet should be encouraged to take prebiotics and/or probiotics to help balance their gastrointestinal flora to help counteract this trend (Reddel et al., 2019).

Intermittent Fasting (IF)

IF consists of periods of reduced or no-calorie intake interspersed with regular caloric intake. This approach postulates that by alternating between different caloric intake levels, participants can address the problematic metabolic adjustment to a consistently reduced caloric intake and subsequent plateauing that occurs with traditional dieting (HTHCSPH, 2018c). Common structures include: 

  • the Eat Stop Eat plan by Brad Pilon requires no caloric intake for two nonconsecutive 24-hour periods each week
  • the Warrior Diet by Ori Hofmekler, which allows eating during only 4 of the 24 hours of each day
  • leangains by Martin Berkhan instructs women to fast for 14 of the 24 hours of each day and men for 16 hours; drinking is allowed during the fasting hours, as long as the drinks are calorie-free
  • alternate-day fasting involves eating meals under 500 calories on 2-3 nonconsecutive days each week; it only allows the equivalent of the number of calories burned on the remaining 4 or 5 days each week

IF diets claim to reduce weight, blood glucose, blood pressure, NIDDM risk, and inflammation and increase human growth hormone (HGH) and longevity. In addition, IF dieting can protect neuronal function and reduce digestive complaints (Fletcher, 2019). A systematic review of 40 studies on IF diets indicated a typical weight loss of 7–11 pounds over 10 weeks. The results indicated no significant difference in weight loss between those following an IF diet and those following a traditional continuous calorie restriction diet. The dropout rates between the groups were also similar, indicating both diets were equally easy to follow. However, the IF group showed some evidence for a short-term increase in LDL levels. IF is not recommended for adolescents, diabetic patients, hypotensive patients, or individuals who are pregnant or breastfeeding. It is also not recommended for patients with a history of an eating disorder (HTHCSPH, 2018c).


The concept of a juice or detoxification diet is rooted in dramatically reduced caloric intake and no solid food for several days. Henning and colleagues (2017) evaluated patients after three days of ingesting a prescribed formula of 6 bottles of fruit and vegetable juices daily. Most participants in the trial had a BMI below 30. The average weight loss in the study was 3.75 pounds. Researchers also found decreased levels of Firmicutes and Proteobacteria and increased Bacteroidetes and Cyanobacteria in participants’ stool samples on day 4 compared to day 0. They also found increased plasma levels of nitric oxide, a vasodilator (Henning et al., 2017). Unfortunately, studies have shown that juicing/detoxification diet weight loss tends to lead to rebound weight gain once a regular food-based diet is resumed (Obert et al., 2017).

The Volumetrics Diet  

In their rankings, the USNWR (2022k) ranked the Volumetric Diet 5th in Best Diets Overall and tied for first in Best Weight-Loss Diets. Barbara Rolls, a nutrition professor at Pennsylvania State University, developed the Volumetrics diet to help people assess a food's energy density and promote satiety. The Volumetrics diet was not designed as a traditional diet plan but is more focused on an individual’s perception of food and approach to eating. Foods are placed into four rankings from very low density (category 1) to high density (category 4). Daily intake should mainly comprise foods from categories 1 and 2, reduced portions of foods in category 3, and nothing from category 4 most of the time. Examples of category 1 foods include non-starchy fruits and vegetables, skim milk, and broth soups. Category 2 foods include starchy fruits and vegetables, grains, cereals, lean meats, legumes, and low-fat mixed dishes. Category 3 foods are most meats, cheese, pizza, french fries, salad dressing, bread, pretzels, ice cream, and cake. Category 4 includes crackers, chips, chocolate, cookies, nuts, butter, and oil. A daily meal plan consists of three meals, two snacks, and a dessert. Followers are encouraged to exercise moderately for 30 minutes daily (USNWR, 2022k).

The program's advantages are its flexibility, abundance of filling food options, and lack of off-limit foods; however, critics comment on the lengthy meal preparation. The flexibility of the diet allows individuals to choose foods that are on sale or in season, keeping grocery costs down, and there is no membership required to follow the diet plan. Books from Barbara Rolls and other authors contain recipes and sample meal plans. The purpose of the diet is to give an individual the tools and education needed to make healthier choices and substitutions on their own (USNWR, 2022k).


The low fermentable oligosaccharides (fructans and galactooligosaccharides [GOS]), disaccharides, monosaccharides, and polyols (FODMAP) diet limits the consumption of high-FODMAPs, which are fermentable, hard to digest, short-chain carbohydrates commonly found in certain foods. Consumption of high-FODMAP foods can exacerbate gastrointestinal (GI) disorders such as irritable bowel syndrome (IBS). IBS affects 1 in 10 Americans each year. Symptoms include abdominal cramping, diarrhea, gas, and bloating, which can negatively impact a patient’s quality of life. One treatment approach to managing IBS symptoms includes avoiding trigger foods. The low-FODMAP diet has been shown to help identify and eliminate the foods that cause the symptoms commonly associated with IBS. One study found that 76% of IBS patients who followed the diet noted improved symptoms (Harvard Health Publishing, 2019). Finding the right diet can control symptoms so effectively that medication is no longer needed for some patients. Since the human body cannot easily absorb FODMAPs, intestinal bacteria have the opportunity to metabolize the undigested carbohydrates, leading to increased fluid and gas in the bowel. This build-up of gas and fluid leads to bloating and affects the speed of digestion, eventually causing pain, diarrhea, or constipation (Cleveland Clinic, 2019). 

The low-FODMAP diet is a three-step elimination diet used to identify the foods to which an individual is sensitive. In the first step, all high-FODMAP foods are eliminated. This stage should only last 2-6 weeks due to how restrictive it is. During the second step, high-FODMAP foods are slowly introduced individually, with the patient monitoring themselves to determine which foods are causing their IBS symptoms. Once troublesome foods are identified, they can be avoided to help IBS symptoms subside (Johns Hopkins Medicine, n.d.). Foods within each category that individuals with IBS should minimize include:

  • lactose: cow’s milk, yogurt, custard, cottage cheese, and ice cream
  • fructose: some fruits (apples, pears, cherries, peaches, and watermelon), honey, and foods containing high fructose corn syrup
  • fructans: certain vegetables (artichokes, asparagus, broccoli, garlic, and onions)
  • GOS: chickpeas, lentils, kidney beans, and soy-containing products
  • polyols: certain fruits (plums, peaches, apricots, nectarines), vegetables (cauliflower and mushrooms), and sweeteners such as mannitol, sorbitol, and isomalt

Instead of these high-FODMAP foods, individuals with IBS should substitute low-FODMAP foods:

  • dairy: lactose-free or plant-based milk, yogurt, and hard cheeses
  • fruit: bananas, kiwi, oranges, and strawberries
  • vegetables: carrots, chives, cucumbers, eggplant, lettuce, olives, and potatoes
  • protein: beef, pork, chicken, fish, eggs, or tofu
  • nuts/seeds: almonds, peanuts, and pine nuts
  • grain: oat bran, rice bran, gluten-free pasta, corn, and quinoa

Importantly, the goal is not to permanently eliminate every food within a specific category but to determine which foods cause GI symptoms, as some will be tolerated better than others. Before starting this diet, patients should contact their HCPs and meet with a registered dietician to ensure the elimination of high FODMAPs is done in a healthy and balanced manner (Cleveland Clinic, 2019; Harvard Health Publishing, 2019). 

Mobile Applications  

Over the last decade, technology to help individuals manage their weight, diet, and activity level has increased. With the success of smartphones that can act more like pocket-sized computers, applications (“apps”) downloaded onto phones have also evolved. This includes apps specifically designed to track weight loss, exercise, calorie intake, sleep, steps taken, and specific diet plans that give users access to recipes, grocery lists, and virtual weight loss coaches. Mobile technology and these apps have become useful in helping to address the current global obesity epidemic, making consumers more aware of their lifestyle choices, and allowing them to self-monitor their health (Ghelani et al., 2020). 

Reviews are mixed about an apps’ ability to help individuals lose weight effectively (Ghelani et al., 2020). One study showed that mobile health apps were effective in helping obese individuals reduce their body weight by 5%; however, the time it took to achieve this weight reduction varied based on how often the participants entered their daily exercise and dietary intake (Han & Rhee, 2021). Although some studies have shown improvements in BMI, weight, physical activity, and eating habits using mobile health interventions, the data is input by the individual and thus may not be complete. There have also been critiques about the time-consuming and confusing nature of inputting exercise and dietary data into some mobile weight loss apps. This technology is most successful when used as adjunctive therapy to more conventional weight-loss interventions (Ghelani et al., 2020). The NIDDK (2017) recommends that any weight management application or online program have weekly lessons tailored to the client’s needs, support from qualified staff, a plan to track progress, regular feedback, and an option for group/social support if desired. The best mobile diet apps include MyFitnessPal, Cronometer, MyMacros+, Fooducate, and MyPlate Calorie Counter. Also, some of the best fitness mobile apps include FitOn, Strava, Nike Training Club, and the StepsApp Pedometer (Migala, 2022). 

One mobile application gaining publicity is Noom, which utilizes a mobile platform designed to operationalize the DPP developed by the CDC and NIH. The USNWR (2022e) ranked Noom fourth in Best Diet Programs. Instead of focusing on what an individual eats, the Noom approach focuses on the psychology behind the individual’s dietary choices. The app combines exercise and diet-tracking features with direct support from a coach through the app’s messaging feature. Only some coaches are dietitians or nutritionists, but each is expected to have a health and wellness background, undergo training by Noom, and demonstrate empathy and kindness. Potential benefits of this program include the flexibility and support offered. Some drawbacks include a lack of nutritional guidance, the heavy reliance on a mobile device, and costs. The program’s cost is currently $59/month or $99 for 3 months (USNWR, 2022e). 

A recent study looked at the difference in results between the Healthy Weight program (HW) by Noom and the Noom-adapted Diabetes Prevention Program (DPP) among individuals aged 35-85 years old. Users who completed the HW program lost an average of 4.74 kg or 3.5% of their body weight at 16 weeks and 6.24 kg or 5.2% at 52 weeks. Users who completed the Noom-adapted DPP lost 5.61 kg or 5.2% of their body weight at 16 weeks and 5.66 kg or 8.1% at 52 weeks (DeLuca et al., 2020). 

Meal Kit Delivery

With the fast-paced and high-stress lifestyle many people live in today’s world, it can be challenging to find the time to plan, grocery shop, prep, and prepare meals. These challenges make compliance with a number of the diet plans described above difficult. Many companies have come out with meal kit delivery services in response to these challenges. These services gained popularity as a way to eat healthy at home without having to do the work of grocery shopping and meal prep. Although some of these meal options still require the individual to cook, the ingredients are provided and often are already measured out and just need to be put together. Many people have reported that the time it takes to cook one of the meals provided is less than the time required to order and wait for expensive, high-calorie take-out. In addition to the health benefits, these meal services expose people to ingredients and recipes that they may not have tried on their own. As the market for this meal option has grown, many of these companies have developed meal plans specifically designed to accommodate specific dietary restrictions to reach more individuals (Howley, 2022). 

More recognizable meal kit delivery services include HelloFresh, Blue Apron, Nutrisystem, Home Chef, and Fresh n’ Lean. HelloFresh incorporates farm-to-table ingredients into easy-to-follow recipes that take less than 30 minutes to prepare. Many meals are approved by a dietician and are below 650 calories each. HelloFresh offers different meal plans based on particular diets, including vegetarian, pescatarian, and low-calorie. Meal plans start a $7.99 per serving plus shipping, but it is possible to skip a week or only order for two people instead of four to minimize costs or wasted food. Fresh n’ Lean does not require the subscriber to prepare the meals. Instead, the meals come ready-made and must be heated before eating. This delivery plan offers a variety of specialty diet options, including vegan, vegetarian, keto, paleo, Whole30, and even low-carb vegan. All the meals include organic ingredients that are GMO and gluten-free. The cost varies based on the meal plan chosen and the number of meals per week but averages $8.00 per meal. Nutrisystem is also a heat-and-eat style meal kit delivery service. Nutrisystem sets itself apart by offering different meals for men and women. This service focuses on weight loss and offers its subscribers counselor support and nutritionist access. There are different tiers, but the basic plan lasts 4 weeks and costs $9.99 per day for women and $11.64 per day for men. Blue Apron is one of the largest meal kit delivery services. This service delivers easy-to-make meals that are ready in 30 minutes. They also provide flexible meal plans and cater to various dietary preferences. Blue Apron offers lower-calorie recipes recommended by WW, and their meal plans are easily tracked with the WW PersonalPoints plan (Howley, 2022). Due to the number of meal kit delivery options available, it is important to research and determine which company and meal plan will meet each individual's needs.     

Key Takeaways 

Although this list of diets discussed is extensive, it is not exhaustive. Many options are available, and new options appear so frequently that it is hard to keep up with the latest diet trends. Several well-known diets not addressed include the Jenny Craig diet, SlimFast, the HMR program, the Biggest Loser diet, the fertility diet, and the alkaline diet, to name a few. In light of the abundance of dietary approaches, nurses should help educate patients on researching and consulting with their HCP before initiating or changing any eating plan.


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