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

4.0 ANCC Contact Hours AACN Category A

Syllabus

Objectives: This learning activity is designed to allow the learner to:

  1. Define the current epidemic of obesity in the United States and discuss strategies for weight loss
  2. 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 WeightWatchers to help elucidate their basic guidelines as well as potential risks and benefits.
  3. Explore the current research regarding extremely low-calorie diets such as OptiFast to help elucidate their basic guidelines as well as potential risks and benefits.
  4. Explore the current research regarding low-fat diets such as the Ornish diet to help elucidate their basic guidelines as well as potential risks and benefits.
  5. Explore the current research regarding low-carbohydrate diets such as the Atkins and ketogenic diet to help elucidate their basic guidelines as well as potential risks and benefits.
  6. Explore the current research regarding the moderate-carbohydrate diets such as South Beach, low Glycemic Index, and Paleo/Whole30 diets to help elucidate their basic guidelines as well as potential risks and benefits.
  7. Explore the current research regarding plant-based diets such as vegetarian, pescatarian, flexitarian, vegan, and the Nordic diet to help elucidate their basic guidelines as well as potential risks and benefits.
  8. Explore the current research regarding specialty diets such as a gluten-free diet, intermittent fasting, juicing/detoxification, and Volumetrics to help elucidate their basic guidelines as well as potential risks and benefits.
  9. Explore the current research regarding mobile weight management applications for your smartphone to help elucidate their basic guidelines as well as potential risks and benefits.

The purpose of this learning activity is to help nurses and other related 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 United States today.


According to the National Institutes of Health’s (NIH) National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), over 70% of the United States population is either overweight or obese. They define overweight as a body mass index (BMI) of more than 30. See Table 1 below for additional BMI details (U.S. Department of Health and Human Services [USDHHS], 2017). According to the Centers for Disease Control and Prevention (USDHHS, 2019c), the prevalence of adult obesity in the United States was 39.8% in 2015-2016, with roughly 93.3 million adults affected nationwide. They estimate that obesity affects roughly 13.7 million children between the ages of 2 and 19, with a prevalence of 18.5%. The CDC considers a number of associated conditions to be obesity-related, including heart disease, stroke, type 2 or non-insulin dependent diabetes mellitus (NIDDM), and some types of cancer. Obesity is most common among certain ethnic groups and age groups. The prevalence of obesity among Hispanics is highest at 47%, followed by non-Hispanic blacks (46.8%), non-Hispanic whites (38%) and lowest among Asians (13%). Middle-aged adults between 40 and 59 years have the highest prevalence of any adult age group at 43%, while adolescents aged 12 to 19 years have the highest prevalence (20.6%) amongst children. 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 and those within the lower and higher income ranges (USDHHS, 2019c).

Table 1. 

BMI Classifications

General Guidelines from the USDHHS and Others

The general recommendations of the USDHHS for weight loss and healthy weight maintenance include the MyPlate program along with several other similar programs. The USDHHS website allows participants to first calculate the number of calories needed to either achieve or maintain their recommended weight and provides a personalized meal plan based on that number. Recommendations include a goal of 150 minutes of moderately-strenuous physical activity per week, as well as two or more days of muscular strengthening exercises per week to help achieve or maintain goal weight and overall health. For children, recommendations include at least 60 minutes of physically active play per day. They advise against reducing the variety of foods eaten when attempting to lose weight as this may exclude vital nutrients from the diet (USDHHS, 2018). They highlight the importance of first talking to your healthcare provider prior to starting any diet or weight loss plan. The guidelines emphasize that any weight loss program should contain behavioral treatments and lifestyle counseling (usually multiple one-on-one or group sessions over a timespan of months), as well as address key issues such as sleep and stress management. The program should provide ongoing monitoring, feedback and support as well as a long-term maintenance plan to prevent weight regain. Weight loss should be slow and steady with a realistic goal of losing 5-10% of body weight over a six-month period. They suggest asking any potential weight loss program about typical results, any evidence they may have published in scientific peer-reviewed journals regarding safety and efficacy, as well as what kind of training or education their staff and counselors have. Obviously, cost should also be communicated up front (USDHHS, 2017). While the Mayo Clinic (2018) has developed their own diet program, which will be reviewed later in this activity, their public website addressing healthy weight loss makes many of the same suggestions seen above, as well as recommending that the patient consider their own personal past (what has worked for you before?), household budget, and likeability of any diet or weight loss program before starting (Mayo Clinic, 2018).

If a patient is interested in attempting weight loss on their own, the CDC (USDHHS, 2018) recommends first assessing baseline caloric intake by keeping a daily log or diary of everything they eat and drink, in addition to an activity log to monitor 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; or the sensation of feeling full. Other suggestions for reducing caloric intake include:

  • Substituting high calorie drinks with water,
  • Decreasing portion sizes,
  • Utilizing low-fat or fat-free dairy products,
  • Utilizing cooking spray in lieu 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 in lieu of potato-based sides such as chips or fries,
  • Eating clear vegetable-based broth soups in place of cream-based,
  • Dipping the fork into salad dressing with each bite while eating a salad instead of pouring the dressing on top,
  • Eating vegetables steamed or grilled instead of fried or sautéed,
  • Adding vegetables to pizza instead of high-calorie meats,
  • Smart snacking with vegetables, fruit, yogurt, air-popped popcorn or dry-roasted nuts (USDHHS, 2019a).

In short, most experts recommend simply to eat wholesome foods in sensible combination, or as the old phrase from writer Michael Pollan describes, “Eat food. Not too much. Mostly plants.” (Katz, 2014).

Regarding exercise, the typical recommendation for moderate intensity exercise most days of the week (see above) has been tested and may not be the ideal suggestion for those looking to lose weight. In 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]), the study indicated that the three diets all achieved short-term weight loss by essentially reducing caloric intake, but that only the HIIT plan improved cardiovascular health and achieved weight loss (Obert, Pearlman, Obert & Chapin, 2017). In their systematic review, Viana et al. (2019) found that when people exercised moderately (heart rate [HR] between 55 and 70% of maximum) for 40 minutes they lost less weight than those that utilized HIIT or a similar method of sprint interval training (SIT). HIIT/SIT was defined in most studies as periods of reaching 80% or more of maximum HR interspersed with recovery periods for a total time of 18-28 minutes. Subjects had a statistically significant reduction in absolute fat mass (-1.58 kg vs -1.13 kg) with the higher intensity, shorter workouts and reported a lower perceived exertion and increased enjoyment. There was a similar effect on blood pressure and insulin resistance in both groups across all studies. Adherence was also slightly better in the higher intensity groups (Viana et al., 2019).

The Mediterranean Diet

The Mediterranean diet was recently ranked by U.S. News & World Report (USNWR, 2019) as the best overall and easiest diet to follow. It was also listed by the Hormone Health Network as one of the three diets that will lead to weight loss (Hormone Health Network, 2019). It promotes a wholesome diet that is predominantly plant-based, with moderate fat and protein intake shown to provide the same cardiovascular benefits as the well-studied and popular Ornish (low-fat) diet (Katz, 2014). It is high in vegetables, fruits, nuts, cereals, whole grains and healthy fats such as olive oil. It includes moderate amounts of fish and poultry with a reduced amount of sugar, red meat (limit to a few times per month) and dairy products. It is low in saturated fats, but high in monounsaturated fats, fiber, and antioxidants. It has been shown in studies to be the most effective at reducing the risk of obesity-related disease such as coronary artery disease, 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, Biagi & Lanari, 2019; HTHCSPH, 2018e). Anton et al. (2017) found one short-term and two long-term randomized clinical trials showing an average weight loss of 7.2% of body weight at three 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 slightly higher weight loss of 10.3% at 12 months (Anton et al., 2017). While the average American diet is comprised of roughly 55% carbohydrates (between 200 and 350 g/day), carbohydrates should account for less than 45% of the daily calories in the Mediterranean diet (Katz & Meller, 2014; Masood & Uppaluri, 2019). The minimally processed food in the Mediterranean diet, as well as the predominance of plants, is thought to lead to health promotion and disease prevention benefits. Studies have also shown decreased insulin resistance, increased longevity, preserved cognition, and even reduction in cancer risk related to the Mediterranean diet. A final benefit is the diet’s recommendation for one to two glasses of red wine daily (Katz & Meller, 2014). The diet encourages a relaxed, social event surrounding meals and encourages regular physical activity. As there is no set daily caloric limit, participants should be encouraged to watch their total caloric intake to encourage any desired weight loss (HTHCSPH, 2018e).

The Dietary Approaches to Stop Hypertension (DASH) Diet

The DASH diet was first introduced at a meeting of the American Heart Association (AHA) in the 1990’s as a treatment option for patients with high blood pressure (Harvard T. H. Chan School of Public Health [HTHCSPH], 2018a). The USNWR (2019) ranked this diet second overall due to its heart-healthy nature but remarked on its high workload required and tendency to be expensive. The diet is mostly plant-based, with the inclusion of low-fat or fat-free dairy products (Katz & Meller, 2014). It incorporates fruits, vegetables, beans, nuts, reduced-fat dairy, whole grains, fish and poultry. It limits sodium (less than 3,000 mg per day) and avoids sugar, red meat, saturated and trans fats. It is high in potassium, magnesium, calcium, and fiber and moderate in protein. If an individual is eating 2,000 calories a day, the diet suggests:

  • six to eight servings of grains daily,
  • four to five servings of fruits daily,
  • four to five servings of vegetables daily,
  • two to three servings of dairy daily,
  • two to three servings of fats/oils daily,
  • less than or equal to six ounces daily of lean meat, poultry, or fish.

The DASH diet also suggests four to five servings per week of nuts and seeds and no more than five servings per week of sweets. The DASH diet has been shown to reduce blood pressure, improve kidney disease, and reduce uric acid levels in patients prone to gout (HTHCSPH, 2018a). It is also reported to reduce the risk of heart failure by as much as 50% and may reduce the risk of depression, stroke, NIDDM, and cancer (Heller, 2019). Despite its many documented health benefits and numerous expert endorsements such as the AHA and NIH, the evidence for its effectiveness as a weight loss tool is lacking (Katz & Meller, 2014). Anton et al. (2017) found only one short-term clinical trial which showed that this diet assisted patients in only a 0.3% loss of body weight at four months. A series of books based on the original DASH diet plan have combined with the Mediterranean diet in attempt to utilize the health benefits of the DASH diet with the weight-loss power of the Mediterranean diet. The combination may produce a low salt, wholesome, and balanced meal plan with weight loss and health promotion/disease prevention potential for patients who can afford the grocery bill and enjoy planning, prepping, and preparing food (Heller, 2019).

The Mayo Clinic Diet

Healthcare providers at the Mayo Clinic developed their own weight loss and lifestyle improvement program called the Mayo Clinic Diet. The USNWR (2019) ranked this diet sixth overall and second for diabetics, remarking that while the diet is flexible and healthy, it could also be expensive and labor-intensive (USNWR, 2019). The second edition of the book, which outlined the diet plan in detail, was published in 2017. The Mayo Clinic’s website describes the plan as being adaptable and capable of helping patients lose between 6 and 10 pounds in the first two weeks (the Lose It! phase), followed by an additional one to two pounds per week thereafter (the Live It! phase). They emphasize 15 key habits of health through their Habit Tracker, 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 intake of fats and sweets. After the first two weeks, women are instructed to eat between 1,200 and 1,600 calories per day depending on current weight, while men’s caloric range is 200 calories more than this. Depending on which calorie limit is appropriate, they suggest between seven and ten daily servings of fruits and vegetables, four to eight servings of carbohydrates, three to seven servings of protein and dairy, and three to five servings of fats. The website also provides a food pyramid to help individuals who need a more visual representation of which foods to focus on (Mayo Clinic, n.d.).

Diabetic Prevention Program (DPP)

The national DPP is an effort to reduce the rates of NIDDM. Developed by the CDC and NIH in 1996, the program emphasizes balance and real food with a successful reduction of NIDDM in 58% of high-risk adults (Katz, 2014). It emphasizes eating a plant-based diet in combination with lean meats and a reduced amount of processed starches and sugar along with exercise (Katz & Meller, 2014). In its current version, it 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 and consists of one-hour weekly meetings for the first six months followed by monthly meetings during the second six months to educate and support participants regarding diet, exercise, stress management, etc. Medicare Part B, as well as some employers and insurers offer coverage for the program, but if a patient is paying out of pocket then prices vary depending on location and administrator. The daily calories needed to maintain current weight is calculated and then 500-1,000 calories are deducted from that to initiate a caloric deficit that leads to sustained but safe weight loss. No more than 25% of daily calories should be derived from fat intake. Daily intake allowed varies from 1,200 calories and 33g of fat daily for an individual weighing between 120-170 pounds up to 2,000 calories and 55g of fat daily for an individual weighing over 250 pounds. Patients are given a pocket guide to help with keeping track and encouraged to keep detailed food and activity logs for accountability (USDHHS, 2019b).

WeightWatchers (WW)

WW was ranked as the 4th diet overall by USNWR (2019), as well as the first in weight loss and amongst commercial plans and second in easiest diets. Their expert panel indicated that participants liked the flexibility of not having any foods off-limits but commented that the program can be expensive. Enrollment fee is $20 to get started followed by $20-$70/monthly depending on the level of support selected (USNWR, 2019). One of the country’s longest-lasting commercial diet programs, WW is a combination of food, physical activity, and behavioral modification plan. It is based on a personalized point system, where foods are assigned point values based on caloric and nutritional value. An individual is instructed to monitor and limit daily point intake to simplify limiting caloric intake. This is combined with weekly accountability sessions (weigh-ins) and educational/group support meetings (Atallah et al., 2014). An online version now allows participants to participate remotely as well. The point system encourages eating less calories, saturated fat, and sugar while encouraging an increased diet of 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 based on age, height, weight, and sex. The program encourages individuals to be active throughout the day in their own ways. A mobile app, Dining Out guide, and a number of “Nearly No Cook” recipes that incorporate grocery store staples and prepared ingredients like rotisserie chicken help to make the program very user friendly (USNWR, 2019). The program has been extensively studied and amongst 26 randomized clinical trials, WW was the only program that was shown to be consistently more efficacious at weight loss at the 12-month mark (considered long-term). The results showed consistent modest weight loss of roughly 3 kg at this time point, versus a loss of 2.2 kg in the control groups. The WW plan also showed evidence of reduced blood pressure in the short-term (although long-term was inconsistent). Studies showed no significant lipid or glucose control changes (Atallah et al., 2014).

Very-Low Calorie Diets (OptiFast)

OptiFast is a commercial weight-loss program by the Nestle corporation (who also funded the main research study cited in their evidence) for patients with a BMI over 30. It is a medically-managed, 12-16-week meal replacement program that advertises an average 30-pound weight loss after 6 months of participation and 25 pounds after 12 months. The meal replacements range from five to six small meals daily (depending on current BMI) for a total caloric intake of 800-960 calories per day, except for individuals with a BMI over 50 who are allowed one small meal per day with 200-250 additional calories). 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 4-6-week period of transition back to food, followed by a maintenance phase that lasts through 52 weeks (The OptiFast Program, n.d.). In their primary efficacy and safety study, 135 patients underwent their OptiFast plan while 138 patients participated in a roughly equivalent low-calorie (500-750 calories below estimated energy expenditure), low-fat (25-30%), food-based program. Both groups had weekly behavioral group sessions during the initial 26 weeks. The OptiFast group had metabolic profiles done 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 four additional medical visits between weeks 27 and 52, while the food-based group had just four medical visits over the 52-week study. Throughout 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 just seven counseling sessions during weeks 1-26 and five during weeks 27-52. Follow-up continued for a total of 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., 2018). The program boasts reductions in participants’ blood glucose, blood pressure, and total cholesterol levels. Advantages may include the simplicity of avoiding grocery shopping and preparing food, as well as avoiding the calculations involved in most diets to reduce caloric or carbohydrate intake. The downside is the obvious lack of choices, as well as the questionable practice of not eating real, fresh food for an extended period of time (The OptiFast Program, n.d.).

The Low-Fat (Ornish) Diet 

The Ornish diet was originally developed by a physician in California, Dr. Dean Ornish, who founded the Preventive Medicine Institute to help people lose weight, gain health, feel better and live longer. It was ranked by USNWR (2019) as the best diet for heart health, but their expert panel found that it could be expensive and difficult to maintain. The program designed by Ornish encourages a diet rich in plants, fiber, as well as some complex carbohydrates. It is very limited in fats (<10% of daily caloric intake), refined carbohydrates, and animal protein. He also incorporates the importance of stress management, exercise, and building emotional health through interpersonal relationships. His diet plan consists of five food categories that help participants fill their grocery carts with the healthiest food choices. It limits cholesterol, oils, excessive caffeine, and nearly all animal products with the exception of egg whites and one cup of skim milk or nonfat yogurt daily. It also allows two ounces of alcohol daily (USNWR, 2019). Experts applaud the diet for its diverse and nutrient-rich nature, and the strong evidence in the landmark study in the 1990s that showed its efficacy in shrinking atherosclerotic plaques and reducing the risk of recurrent myocardial infarction in high-risk adult patients (Katz, 2014). Anton et al. (2017) compared the Ornish diet to six others in his systematic review and found two short-term/long-term trials. These trials involved a total of less than 400 participants and resulted in a 2.9-3.5% weight loss at six months and a 2.6-3.2% weight loss at twelve months (Anton et al., 2017). Unfortunately, the diet has also been misinterpreted by some to allow for the increase in consumption of “low-fat” foods that are high in refined starches and sugar and therefore inefficient calories. Newer iterations of this diet allow a slightly higher percentage of daily fat intake (<20% of daily calories) and focus more on fat modification (think the healthy fats showcased in the Mediterranean, DASH and other diets above) in lieu of fat restriction (Katz & Meller, 2014).

Low-Carbohydrate Diets 

The Atkins Diet

The Atkins diet was developed by Dr. Robert Atkins (a cardiologist) in the early 1960’s and 70’s. It was ranked by USNWR (2019) as on 37th overall (out of 41) but tied for 2nd place for Best Fast Weight-Loss diet. Their expert panel found the diet was full of fatty foods that could be eaten guilt-free and is associated with a quick drop in weight but found the carbohydrate rules very restrictive and voiced concerns about health issues with a diet so high in fat. It was the first in the ensuing low-carbohydrate diet trend that followed, and it originally stressed a very low level of carbohydrate intake and unlimited intake of protein and fats. It is broken down into four phases, and during Phase 1 participants are only allowed 20 g of net carbohydrates (carbohydrate - fiber) daily for a period of two weeks. 12-15 of these need to be derived from what the diet calls “foundation vegetables” such as arugula, cherry tomatoes, and brussel sprouts (USNWR, 2019). During Phase 2, participants slowly add small amounts of berries, nuts, and seeds back into their diet. They continue Phase 2 until ten pounds from their goal weight. During Phase 3, participants are instructed to add roughly 10 g of carbohydrates per week back into their diet through starchy vegetable, fruits, and whole grains until they reach their goal weight. Once at their desired weight, the Phase 4 maintenance involves balanced carbohydrate intake with weight to maintain long-term (Mayo Clinic, 2017b). Atallah et al. (2014) found in their systematic review of 26 randomized trials that the Atkins plan had similar short-term weight loss results as the Zone diet and showed modest results overall. They found the plan may lead to some improvement in high density lipoprotein (HDL) and triglyceride levels but may also increase low density lipoprotein (LDL) levels in the short term. They found the plan may also improve blood pressure short-term, but with inconsistencies in long-term results (Atallah et al., 2014). Anton et al. (2017) found ten trials regarding the use of the Atkins plan in their systematic review ranging from six to twenty-four months in duration. Nine out of the ten showed clinically meaningful weight loss in the short-term, and of the eight long-term trials, six were able to show clinically meaningful weight loss at one to two years. These results were significantly better than any of the other six diet plans that Anton’s team reviewed (Anton et al., 2017). Experts warn that carbohydrate reduction in the absence of calorie reduction may contribute to weight gain as well as adverse metabolic effects. They stress that newer versions of the diet plan published more recently emphasize the limitation of fats and protein as well as the selective use of healthier carbohydrates such as vegetables and beans. They also raise concerns about the environmental and ethical issues surrounding a meat or animal-based diet. The response has been the development of the eco-Atkins diet, which is a similarly high-protein plan that is plant-based. Overall, experts stress that high amounts of saturated fats may have effects in the long-term that are undesirable or unknown, and a high-fiber, carbohydrate-selective diet that limits processed starches and sugars may provide similar and even additional nutritional and health benefits (Katz & Meller, 2014). The Atkins plan should not be recommended for patients with severe kidney disease or women who are pregnant or breastfeeding. Common side effects during the early phases include headache, dizziness, weakness, fatigue, constipation and an increased risk for ketosis. Patients on oral or subcutaneous diabetic medications or diuretics should consult their provider regarding medication adjustments before initiating a low-carbohydrate diet such as Atkins (Mayo Clinic, 2017b).

The Ketogenic (Keto) Diet 

 The Keto diet is a low carbohydrate, high fat, moderate protein diet originally developed and used for the management of seizure disorders. This diet has the ability to therapeutically reduce the amount of seizures by 50% in adults without medication (Reddel, Putignani & Del Chierico, 2019). It has also been used therapeutically in a number of other neurological conditions such as Alzheimer’s, as well as in diabetes, cancer and polycystic ovarian syndrome. The name was generated from ketogenesis, which is a metabolic process within the body during which ketone bodies are produced by the liver from fat stores in the body after three to four days of extremely limited glucose ingestion (HTHCSPH, 2018d). The diet encourages about 55-60% of daily calories from fat, 30-35% from protein (or 1-1.5g per pound of body weight), and 5-10% from carbohydrates (Masood & Uppaluri, 2019). Some versions of the plan allow up to 80% of daily calories from fat. Foods that are eliminated 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 warned to limit protein intake to moderate levels to avoid interference with 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, 2018). 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 the keto diet to improve glucose control as well as reduce weight, blood pressure, blood glucose, and triglycerides, but long-term studies are lacking. The diet is deemed safe to continue for 6-12 months in otherwise healthy patients, but renal function should be monitored during that time and patients should be instructed to resume more normal diet patterns gradually after that time. Patients should be warned about the risks of the Keto diet carefully. In the short term, patients may experience headache, nausea/vomiting, fatigue, dizziness, and insomnia (called the “keto flu”) that may last for a few days to weeks. Similar to the Atkins plan above, diabetic and diuretic medications should be reviewed before starting the diet. Due to the increased stress on the body, and specifically the liver, a 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 palmitoyl transferase deficiency, carnitine translocase deficiency), porphyria, or pyruvate kinase deficiency. There may be an associated increase in LDL levels with a Keto diet (Masood & Uppaluri, 2019). Experts also warn that any diet high in saturated fats, as the Keto diet most assuredly is, may increase an individual's risk for heart disease. The Keto diet may also lead to nutritional deficiencies in selenium, magnesium, phosphorus, vitamin B, and vitamin C (Harvard Health Publishing, 2018). Keto diet may also increase uric acid levels and increase an individual’s risk for kidney stones and osteoporosis (HTHCSPH, 2018d).Studies have also shown that participants eating a ketogenic diet have an increase in healthy gut bacteria, but overall a decrease in bacterial diversity in their digestive tract. This lack of diversity could negatively impact one or more of the many essential functions of the human gut microbiota (Reddel, Putignani & Del Chierico, 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 amount of ketone bodies circulating, creating a metabolic acidosis that requires immediate medical treatment (HTHCSPH, 2018d). In addition, the same concerns exist regarding environmental and ethical issues surrounding a meat or animal-based diet (Katz & Meller, 2014).

Moderate-Carbohydrate Diets

The South Beach Diet

A moderate-carbohydrate diet, such as South Beach, was listed by the Hormone Health Network as one of the three diets that will actually lead to weight loss (Hormone Health Network, 2019). Originally developed to help participants choose good carbohydrates and good fats and avoid bad carbohydrates and bad fats, the USNWR (2019) ranked this diet 20th overall and 4th amongst commercial diet plans. Originally developed by another cardiologist, Dr. Arthur Agatston, who published a book detailing the plan in 2003. Short term studies show the plan may reduce weight as well as total cholesterol (Mayo Clinic, 2017c). This diet encourages six small meals daily comprised of lean meats, lots of vegetables, as well as some fruits, low-fat dairy, healthy monounsaturated fats, and complex and low glycemic-index (GI) carbohydrates. It avoids sugar but allows two servings of alcohol per week. The plan encourages 30 minutes of exercise daily during the acute weight loss phase, and 60 minutes daily during the maintenance phase (The Official South Beach Diet, n.d.). The original plan was broken down into three phases. Phase 1 last two weeks and is designed to cut out almost all carbohydrates in order to eliminate cravings for sugary, sweet, and starchy foods. Phase 2 is the long-term weight loss phase where whole grains, brown rice, and some previously-avoided vegetables and fruits are gradually reintroduced until the patient reaches their goal weight. Phase 3 starts at goal weight and allows the careful balancing of carbohydrate intake and weight for life (Mayo Clinic, 2017c). The latest version of the South Beach Diet now includes a mail-order meal delivery service. The current plan reduces Phase 1 eating to one week, followed by three weeks of Phase 2 meals delivered to clients’ doors. They advertise a seven-pound weight loss in the first week followed by one to two pounds a week after this. A plan that includes three meals and two to three snacks and dessert daily ranges from $300-400 for a four-week period. Participants may also download the South Beach mobile app for additional support and features. They also have a plan designed specifically for patients with NIDDM (The Official South Beach Diet, n.d.). In addition, the same concerns exist regarding environmental and ethical issues surrounding a meat or animal-based diet (Katz & Meller, 2014).

Glycemic Index (GI) Diet

The GI diet limits carbohydrate intake based on their overall effect on a person’s blood glucose level. Some carbohydrates create an immediate spike in blood glucose, while others create an increase that is less intense and slower. This diet may also be termed the Slow Carb diet and the concept is used in the Zone diet as well as SugarBusters (Mayo Clinic, 2017a). The GI diet limits all fruits, and some vegetables, as well as any processed starches and sugars. It is high-fiber and often plant-based rather than high-protein. Studies show that this diet may reduce insulin resistance and inflammation while lowering cardiovascular risk and the risk of developing NIDDM (Katz & Meller, 2014). This diet provides each food with 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 issues with this grading system is that the GI score of a food ignores the serving size. In addition, the list contains only those foods that have been studied and is therefore not an exhaustive, comprehensive list. For this reason, nutritionists, dieticians and other healthcare professionals developed glycemic load (GL) which is devised to calculate the GI of a food in one standard serving size. 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 breads. High GL (20+) foods include white rice, white bread, and potatoes. Critics of this system point out that GI and GL do not take into account how foods are prepared or processed, what foods are eaten in combination together, or their overall nutritional value. Studies of diets based on GI or GL are mixed but may lead to weight loss as well as a reduction in total cholesterol and LDL levels (Mayo Clinic, 2017a).

Paleo/Whole30

The Paleolithic (Paleo) diet is a pattern of eating that is meant to mimic the nutritional pattern seen in humans during the Paleolithic era. There are multiple sources of information about what this means and how it should be interpreted, which may make following this plan frustrating. Even Paleo experts disagree about what humans consumed during the Paleolithic era and how best to replicate that today. The general premise is to avoid processed foods and increase daily intake of vegetables, fruits, nuts, seeds, and lean meats. There are no dairy products or grains allowed on the Paleo diet, and fat intake should be limited to between 25-40% of daily caloric intake. Most plans agree that both 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 (HTHCSPH, 2018f; Katz & Meller, 2014). Most Paleo plans advocate for grass-fed beef, salmon, and eggs for protein and encourage olive oil for a healthy source of monounsaturated fats. The majority limit both salt and sugar and do not allow beans, legumes, alcohol, coffee, or any processed food during the plan. Complex carbohydrates such as sweet potatoes and cassava may be eaten in moderation. 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 with the Paleo diet (HTHCSPH, 2018f). Anton et al. (2017) found just one short and one long-term clinical trial which showed an average weight loss of 9% in Paleo dieters at six months and 10.6% at twelve months. When compared with the Nordic diet (see below) in a large randomized trial, Paleo dieters lost significantly more fat mass at the six-month mark, but not at the 24-month point. Critics point to the meal plan’s potential increased cost at the grocery store, high-maintenance meal planning, and potential ethical and environmental concerns regarding a diet consisting of animal products (HTHCSPH, 2018f; Katz & Meller, 2014). The purists also argue that the caloric output of Paleolithic human is quite dramatically different from the modern human, making the entire premise invalid (Katz & Meller, 2014). Patients should be warned regarding potential nutritional deficiencies in calcium, vitamin D and vitamin B that may result from any moderate or prolonged use of this diet (HTHCSPH, 2018f).

Whole30 is a lifestyle plan based on the basic premise of 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 all sugar, dairy products, grains, alcohol, and legumes. The intention is to avoid the hassle of having to count calories and encourage dieters to enjoy food prepared fresh at home. Critics comment on the plan’s elevated cost at the grocery store, the high-maintenance food planning, and the lengthy preparation process. It is a short-term plan only intended to be followed for 30 days (which may reduce many of the risks mentioned above), after which participants are instructed to slowly and individually reintroduce additional foods back into the diet to assess the body’s reaction to those foods (Step One: Discover the Whole30, n.d.).

Plant-Based Diets 

Vegetarian/Pescatarian Diet

Vegetarian diets are typically plant-based, naturally lower in fat, higher in fiber, and may or may not include eggs and/or dairy products. A vegetarian diet that includes fish and fish 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, decreased risk for cardiac events and cancer, and overall reduced mortality. In addition, it does not carry concerns regarding the environmental and ethical issues of sustaining a meat or animal-based diet (Hormone Health Network, 2019; Katz & Meller, 2014). Studies have also linked plant-based diets to improved lipid profiles and 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 intake to ensure it does not go above 1,000 mcg/day. Large doses of folic acid can lead to increased lipid stores and weight gain in rats. Symptoms of high levels of folate can cause symptoms such as nausea, anorexia (loss of appetite), confusion, irritability, and sleep disturbance (Kelly et al., 2016). There is a concern regarding some nutritional deficiencies, such as vitamin B12, for strict vegetarians. Vitamin B12 is a water-soluble vitamin that is crucial in red blood cell formation, neurological function and DNA synthesis. Fortified foods (meat analogues, cereals, nutritional yeast, protein bars, soy or rice milk) and/or supplements should be recommended as well as periodic screenings for deficiency for all vegetarians to maintain adequate B12 levels. A normal B12 level should be between 170-250 pg/mL. The recommended daily allowance of B12 is between 0.4-1.8 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 be supplemented 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 paresthesias, depression, confusion, weakness, constipation, diminished appetite, weight loss, or a sore mouth/tongue (Palmer, 2018). Other deficiencies that may 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 (Hormone Health Network, 2019). Calcium and vitamin D can be found in most dairy products, and iron can be found in fortified breads and cereals as well as beans, lentils, raisins, and blackstrap molasses. Fish is a plentiful a source of omega-3 fatty acids, and fortified eggs can be used as well. Vegetarian women who are pregnant or breastfeeding should be encouraged to eat about 1.1 g/kg/day of protein, between 4-50 mcg/day of B12 (although some nutritionists advise up to 250 mcg/day is safe), 600 mcg/day of Vitamin D, 220 mcg/day of iodine, and 1500 mg/day of calcium (Sebastiani et al., 2019).

Flexitarian Diet

USNWR ranked the flexitarian diet as 3rd overall and 2nd amongst plant-based diets. A 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. 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. Blatner also focuses on emotional health, flexibility, and a pursuit of gradual progress, not perfection. She gives participants permission to cheat and rarely eat meat when cravings hit. The plan encourages at least 30 minutes of exercise five days per week. Experts point out 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 those that do not enjoy fruits and vegetables. The plan advertises that it can help people lose weight, reduce the risk of heart disease, NIDDM and cancer and increase longevity (USNWR, 2019).

Vegan Diet

A vegan or whole-food plant-based (WFPB) diet is one that avoids all animal products. Karlsen et al. (2019) found average vegan diets with 180% more vegetables, 460% more legumes, 100% more whole fruit, 132% more whole grains and 74% less refined grains versus an average diet based on the MyPlate standards. A WFPB diet specifically limits processed foods and refined sugars, fats, and salts in addition to 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 a score of 88/100 (Karlsen et al., 2019). Deficiencies in vitamin B12 are common and can be serious, as well as calcium and vitamin D. As aforementioned with vegetarians, these need to be supplemented if dietary intake is deficient. Palmer (2018), a registered dietitian, recommends all vegans supplement with 250 mcg of vitamin B12 daily. Short and medium-term studies show a trend towards improved dietary quality, reduced inflammation, reduced cardiac risk factors, reduced cancer risk, improved anthropometry, and improved insulin sensitivity amongst people on a vegan diet (Katz & Meller, 2014). Kahleova et al. (2019) found that when people transitioned to a vegan diet, their average fat intake reduced from 36.1% of daily calories to 17.5% of daily calories. This reduction in saturated and trans fats, in combination with a relative increase in the percentage of healthy polyunsaturated fats, lead to a reduction in fat mass as well as insulin resistance and enhanced insulin sensitivity. The average weight loss seen was 6.5 kg over the 16-week course of the study, with a 4.3 kg reduction in fat mass (Kahleova, 2019). Many of the nutritional deficiencies seen in vegetarians can be worsened in vegans if careful consideration is not taken into account for nutritional balance and supplementation (Palmer, 2018; Sebastiani, 2019).

Nordic Diet

The Nordic diet was ranked ninth overall by the USNWR secondary to its ability to help patients lose weight and reduce inflammation as well as reduce the risk of NIDDM. The plan was developed at the University of Copenhagen. While it does not avoid all animal products, the plan advocates for a focus on protein sources from seas and lakes predominantly (USNWR, 2019). Only about 15% of daily calories should be derived from protein, with 25-30% coming from fat and 55-60% derived from carbohydrates (HTHCSPH, 2018f). When meat is eaten in limited quantities, high-quality meat from wild landscapes should be chosen. The diet should be based predominantly on organic, local, seasonal fruits and vegetables and whole grains prepared at home in a social, relaxed environment with family and friends. The diet emphasizes low GI/GL carbohydrates in at least a 2:1 ratio with proteins. The concept is to create a diet that is healthy and lower in waste/more environmentally friendly, but critics point out that eating in this manner can be expensive, time consuming and not always practical (USNWR, 2019). 

Specialty Diets

Gluten Free (GF) Diet

A GF diet excludes wheat, rye, barley, and hybrid grains such as kamut and triticale. Originally developed to treat a condition of gluten intolerance called Celiac Disease which affects 1-2% of Americans, this diet has gained more popularity in recent years amongst people without Celiac Disease. Up to 6% of Americans have a gluten sensitivity, which is not as severe as Celiac Disease but involves gastric symptoms when moderate or large quantities of gluten are eaten. Despite these low numbers, up to a third of surveyed Americans report eating a diet of reduced or completely eliminating gluten. Gluten can be found in sauces such as soy sauce and malt vinegar, maltodextrin, wheat starch, breads, pasta, cereals, and processed snacks. The concept of the diet is to replace these foods with increased amounts of fruits, vegetables, and grains like brown rice, quinoa, and millet. The issues that have started to develop include the development of replacement 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 that have a true gluten sensitivity or intolerance. Evidence supporting a GF diet for weight loss is lacking. It may potentially lead to weight gain if there is a reduction in dietary fiber as is seen with some GF diets and an increase in portion sizes due to a perceived impression of GF foods being healthier. Processed GF replacement products are also typically more expensive than their traditional counterparts. Patients should be cautioned about potential for nutritional deficiencies in vitamin B, iron and calcium due to a GF diet, as well as potential for an increase in cardiovascular risk if there is a reduction in dietary fiber (HTHCSPH, 2018b). Studies of bacterial flora indicate that a GF diet reduces the number of healthy bacteria such as lactobacillus and enterococcus and an increased amount of Bacteroides, staphylococcus, Salmonella. To help counteract this trend, individuals on a GF diet should be encouraged to take pre or probiotics to help balance the gastrointestinal flora (Reddel, Putignani & Del Chierico, 2019).

Intermittent Fasting (IF)

The practice of IF consists of periods of reduced or no calorie intake interspersed with normal caloric intake. The theory postulates that by alternating between different levels of caloric intake, participants are able to address the problem of the body’s metabolism adjusting to a consistently reduced caloric intake or plateauing that occurs commonly in traditional dieting (HTHCSPH, 2018c). Common structures used include:

  • Eat Stop Eat plan which requires no caloric intake for two nonconsecutive 24-hour periods each week by Brad Pilon.
  • The Warrior Diet by Ori Hofmekler which allows eating during only four 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 instructs less than 500 calories to be eaten two or three nonconsecutive days each week, and only allows 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 as well as increasing human growth hormone (HGH) and longevity. They claim IF dieting can protect neuronal function and reduce digestive complaints (Fletcher, 2019). A systematic review of 40 studies looking at IF diets indicated a typical weight loss of between 7-11 pounds over a period of 10 weeks. Unfortunately, there was not a 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. The IF group showed some evidence for 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).

Juicing/Detoxification

The concept of a juice or detoxification diet is rooted in dramatically reduced caloric intake and no solid food for a period of several days. Henning et al. (2017) evaluated patients after a three-day period of ingesting a prescribed formula of six bottles of fruit and vegetable juices daily. Most participants in the trial had a BMI less than 30. The average weight loss in the study was 3.75 pounds, and they found decreased levels of Firmicutes and Proteobacteria and increased Bacteroidetes and Cyanobacteria in the stool samples of participants on day 4 as 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 weight gain once a normal food-based diet is resumed (Obert, Pearlman, Obert & Chapin, 2017).

The Volumetrics Diet

Barbara Rolls, a nutrition professor from Pennsylvania State University, developed the Volumetrics diet to help people assess the energy density of a food and consequently fight hunger. Foods are placed into four categories ranking them from very low density (category 1) to high density (category 4). People are encouraged to exercise moderately for 30 minutes daily and eat three meals, two snacks, and dessert. Daily intake should be made up of mostly foods from categories 1 and 2, reduced portions of foods in category 3, and to avoid category 4 foods 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, cheeses, pizza, french fries, salad dressing, bread, pretzels, ice cream and cake. Category 4 includes crackers, chips, chocolate, cookies, nuts, butter, and oil. Advantages of the plan are that it is flexible, there is plenty of filling food and there are no foods that are off limits, but critics comment on the lengthy meal preparation. In their rankings, the USNWR ranked the Volumetric Diet 6th overall and 2nd for weight loss (USNWR, 2019).

Mobile Applications

The use of technology to help people manage their weight, their diet, and track their activity has increased over the last several years with the success of smartphones that are able to do and carry more in a pocket-sized computer. Bardus, van Beurden, Smith & Abraham (2016) reviewed several weight-loss, weight-management and activity applications and found 70% were free, and 13 of 23 tracked weight, food/caloric intake, and activity. The best-rated were YouFood (IOS), Weilos (IOS), and the Ultimate Food Value Diary (android). Unfortunately, they found an overall paucity of evidence-based educational content. Most applications were based on control theory with goal setting, self-monitoring and provision of feedback features. Only two out of the 23 applications reviewed built behavioral skills (Bardus et al., 2016). The National Institute of Health (USDHHS, 2017) recommend that any weight management application or online program should 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. A newer application to hit the market, Noom, utilizes a mobile platform designed to operationalize the DPP developed by the CDC and NIH. A recent study of 43 patients with a BMI > 30 who started utilizing Noom found 36 patients who completed the 24-week program. Of those 36 patients, 64% lost greater than 5% of their body weight within the 24-week timeline. The mean weight loss was 7.5% amongst those 36 patients that completed the study. The cost of the program is currently $59/month or $199/year (Michaelides, Raby, Wood, Farr & Toro-Ramos, 2016).

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