Mya Care Blogger 04 Aug 2021

This article forms part 5 of a health and wellness series on diet. 

Part 1 discusses dietary guidelines and components.
Part 2, Part 3, Part 4 & Part 5 reviews 24 popular diet plans across 7 major dietary categories.
Part 6 concludes the review with the debunking of common dietary myths and a summary of the key findings.

Diets that Focus on Calories and Carbs

Calories describe units of energy, particularly pertaining to cellular energy metabolism and the amount of “stored energy” in foods. 

With the boom in biological research in the last few decades, an understanding of cellular energy metabolism has dramatically improved, revealing multiple cellular pathways that contribute and affect energy metabolism. This essentially reduced the value of calories as a tool for optimizing nutrition as there are many other factors involved in the amount of energy cells can produce. 

Nevertheless, studies looking at caloric restriction have proven that caloric restriction (in the absence of malnourishment) is associated with longevity [1], improved cardiovascular parameters [2], weight loss and maintaining a healthy weight [3]. 

Thus, low carbohydrate diets became very popular for inducing weight loss [4], based on the concept of caloric restriction. Extreme versions tend towards the likes of high protein diets (and their contraindications), as fats are considered a high calorie food. 

Subsequent advances in the understanding of cellular metabolism made it clear that caloric restriction is not as simple as caloric intake, revealing the flaw in this line of thinking. 

The applied concept of calories changes subtly depending on whether one is looking at carbs, fats or proteins. While carbohydrates and proteins were always considered low in calories compared to fats; fats and proteins require more calories in order to produce cellular energy than carbs, resulting in weight loss and potentially less available energy. 

In this sense it is difficult to generalize with dietary carbohydrates and calories. It appears more beneficial to focus on consuming low calorie carbohydrates than it is to avoid high calorie foods, such as fat, or to consume fewer carbohydrates in order to avoid calories. 

16. Zone diet

The Zone Diet was devised more than 30 years ago by Dr. Barry Sears in order to reduce diet-induced inflammation and promote long-lasting health and well-being. The diet arose from a solid basis of evidence that proves that in most chronic lifestyle diseases, inflammation plays a leading role. [5] 

Dr. Sears makes use of blood testing in order to monitor and improve three specific ratios that pertain to overall health. These ratios are commonly used in scientific studies as markers for different types of systemic inflammation. If the levels of these three ratios fall within healthy parameters, then one is “in the zone”. They include:

  • Triglyceride to high-density lipoprotein cholesterol ratio (cholesterol balance).

  • Arachidonic acid to eicosapentaenoic acid ratio (omega-6 and omega-3 lipid profile).

  • HbA1c levels (assesses blood glucose levels).

Staying “in the zone” demands consuming nutritious wholefoods and avoiding processed foods. The diet is low in carbohydrates (40%), and moderate in protein (30%) and fat (30%). Each meal and snack needs to be balanced accordingly, consisting of: 

  • One third lean protein, which includes lean beef, wild game, poultry, fish, egg whites or low-fat dairy.

  • Two thirds carbohydrate, composed of a vibrant mix of colorful vegetables and a small amount of fruit. Carbs are to be low in starch and sugars (low GI).  

  • A little portion of monounsaturated fat; sources of which include olives, almonds, avocado or their cold-pressed oils.

Calories are counted on the Zone diet, with 1200 being allocated to women and 1500 to men. Consistent exercise is another component of the Zone Diet’s program. [6]


The advantages of the Zone Diet are purported by scientific research carried out by Dr. Sears himself [7]. He has claimed that the benefits of the diet include the following:

  • Increased weight loss.

  • Maintaining optimal health and wellness.

  • Enhanced athletic performance.

  • Improved cognition.

Other researchers testing the diet's efficacy did not find that it improved athletic performance. There is insufficient evidence to support the other claims. However the diet is likely to improve general health and well-being for those leading an unhealthy lifestyle, as it is higher in nutrition than the average Western diet. 


The Zone diet has been heavily critiqued as being based off of unsound nutritional science, with contradictory evidence pertaining to its efficacy. Major disadvantages pertaining to the diet include:

  • The only claim scientifically tested for would be its enhancement of athletic performance, which proved to be false or negligible. [8][9]   

  • While other claims may be true, they remain scientifically untested in the context of the diet plan itself and are based off of cellular interactions that have yet to be proven at the human level. [10]

17. South Beach diet

The South Beach diet is a very popular commercial diet plan revolving around low carb intake. It was originally a modified version of the Atkin’s Diet that is less extreme and more nutritionally balanced in order to maximize weightmaximize on weight loss in a healthy fashion. The creator made use of other health principles, such as reducing saturated fat intake and splitting the diet into three phases, the first of which resembles an elimination diet.

Carbohydrates are not restricted to very low levels as seen in the Atkin’s Diet. In the first phase, around 45% carbs are recommended before being dropped to around 28% in later phases [11]. Of carbohydrates consumed, there is an emphasis on fiber-rich vegetables, herbs, spices and foods containing monounsaturated fats like nuts and seeds. Lean meat, legumes and low-fat dairy are consumed as further sources of protein and fat. Sugar, fruits, grains and starchy vegetables are cut out of the diet until the second phase. Alcohol is not permitted on this diet until the third and final phase.

Like an elimination diet, phase two demands adding back foods that were barred in phase one. This phase continues until a healthy weight is reached. In phase 3, the participant can consume any food in moderation whilst following the health principles learned during the process.

Regular exercise and healthy lifestyle habits are encouraged for optimal results. An exercise plan accompanies later renditions of the diet. [12]

The South Beach Diet is a commercial diet plan that has grown to now offer its subscribers meal deliveries which cater to the diet and its phases. A ketogenic version of the diet is also available as of 2019.


Advantages of South Beach include:

  • Promotes weight loss in overweight individuals.

  • Safer than the Atkin’s Diet in terms of cardiovascular disease risk.

  • Encourages a healthier eating pattern for life.

  • Increased consumption of fiber-rich vegetables and unsaturated fats as well as reduced consumption of refined foods may reduce heart disease risk . [13]

  • May improve gut health in a similar fashion to an elimination diet (see autoimmune protocol diet).


Disadvantages associated with this diet are listed below:

  • Not enough scientific evidence to validate the diet plan. [14][15]  

  • Risk of inducing ketoacidosis in some individuals [16]. 

  • May be too restrictive on fats.

18. Weight Watchers Diet (WW diet)

The Weight Watchers Diet plan is more of a diet scheme where the dieter makes choices based on the points allocated to them on a daily basis. No food is completely off limits and no portioning or nutrient calculations are required to implement it. Foods are ascribed points based off their fat, calorie and fiber profile with unhealthier options weighing more on the WW system. This limits their intake and places an emphasis on consuming healthy foods.

The diet is guided with the help of an app, which contains all the relevant information about the points allocated to foods. The user is required to buy a diet plan, of which there are three types that vary in their strictness and aims . The original aim of this scheme was to promote weight loss, however it also tends to promote a healthier eating pattern. 


Evidence is limited regarding the effectiveness of this diet scheme. Some potential advantages include:

  • Adherence is associated with gradual, steady weight loss [18].

  • Encourages healthier eating habits.

  • May improve life quality in the long term [19].


WW is prone to the following pitfalls:

  • The diet does not strictly limit unhealthy foods which may lower its effectiveness.

  • It may be pricey for some individuals [20].

  • There is limited information regarding its long-term safety.

  • Adherence can be tedious as one needs to fill in information on every food consumed on a daily basis.

19. Volumetrics Diet plan

The Volumetrics diet is a diet that works according to the calorie density of foods. The calorie density of the food describes how many calories the food possesses per gram. 

Barbara Rolls, the inventor of this diet plan, attempted to make losing weight easier through restricting caloric intake but not the amount of food [21]. She realized that people will generally consume a similar amount of food each day by weight in order to feel full. Instead of starving the person, she advocates consuming healthy foods with a low caloric density, thus restricting calories and not food intake. The individual eats as much food as they need to feel full and can still lose weight. [22]  

A diet low in caloric density is likely to resemble a low-fat, high fiber diet. Foods with a low calorie density include fruits, vegetables, whole-grain pasta, lean poultry and low-fat dairy. Fruit and vegetables are allowed at all times, whereas other foods higher in energy density are restricted accordingly. Processed foods and foods high in either fat or sugar have a high calorie density and are carefully managed. 

The recipes contained within the 12 week diet plan describe how sneaking in extra low-calorie vegetables into one’s meals decreases the total caloric density of the food. Further details of the Volumetrics Diet can be found in Barbara Rolls books, where exercise and other healthy lifestyle habits are adopted as part of the diet plan.


Provided the Volumetrics Diet is nutritionally balanced, it may confer the following advantages:

  • Promotes weight loss [23][24].

  • Helps to broaden an understanding of low-calorie, nutrient-dense foods and moderate unhealthy eating patterns.

  • May improve overall health and well-being through increased fruit and vegetable consumption.


The Volumetrics Diet is generally regarded as safe and effective for the purpose of weight loss. 

Disadvantages include:

  • Adherence may be low.

  • It limits healthy fat intake.

  • Prone to misapplication and over-consumption of unhealthy low-calorie foods that lack adequate nutrition (such as artificial sweeteners) [25].

20. Nutritarian Diet

The nutritarian diet was developed by Dr Fuhrman and released to the public in 2003 in his book titled “Eat to Live.” It places maximum emphasis on plant-based, nutrient-dense wholefoods and attempts to almost fully do away with animal products and most processed foods. It follows a unique food pyramid that is dictated by the calorie count and nutrient density of foods [26]. 

All vegetables excluding potato are to be eaten in the largest quantities, consisting of 30-60% of one’s daily food intake. Half of this intake should be made of raw vegetables. Fruits, nuts, seeds and legumes ought to each consist of 10-40% of the diet. Whole grains and potatoes are restricted to less than 20% of one’s intake, while eggs, oil, dairy and wild lean animal products constitute less than 10%. 

Processed foods, sweets, cheese and commercially farmed animal products are to be avoided and consumed very rarely, if at all. Salt, oil and sugar are restricted and not used in cooking. In the case of oil, the wholefood source of oil is encouraged more than an oil extraction. Salt intake is limited to less than 1g a day. [27]

Consumption of fully balanced meals is encouraged instead of snacking. One meal of the day needs to be a vegetable salad, topped with a nut or seed based dressing. The first 6 weeks of the diet plan is stricter and sticks to only unrefined, plant-based foods [28]. According to some sources, the diet advocates making use of natural supplements to prevent any potential nutrient deficiencies, especially if one follows a strictly plant-based version of the diet. These include a multivitamin containing B12, iodine, zinc, Vitamin D3 and algae oil.

Dr Fuhrman is of the opinion that cutting out all processed foods and animal products is a healthier practice that promotes overall well-being [29]. Furthermore the diet emphasizes consuming a wide, colorful variety of plant-based foods as these are the highest in micronutrients that are associated with longevity and disease prevention.

For those wishing to transition into a fully plant-based diet plan, this may be a great place to start.


The pros of the nutritarian diet may include:

  • Without calorie counting, the diet is naturally low in calories by design perhaps making it easier to follow than other low calorie diets. 

  • Promotes well-being and gradual healthy weight loss [30].

  • May help lower cardiovascular disease risk by reducing cholesterol and serum lipids [31].


The cons include:

  • The diet may be too strict for some people to follow

  • May be too restrictive on healthy fats.

  • Not everyone can afford health supplements and not all supplements are without adverse long-term effects.

  • May leave one hungry until the initial phase is over and one has adjusted to the diet.

21. Macrobiotic diet

A macrobiotic diet is a very high carb diet (71%) that emphasizes consuming a large variety of unrefined whole grains, legumes, sprouts, vegetables, and non-tropical fruits. The diet has been around since before the 1960’s, when it first rose to popularity, and is aimed at improving overall health and well-being. The macrobiotic diet encourages participants to adopt a positive mindset and a philosophy of balance as part of living a healthy lifestyle. [32]

40-60% of one’s intake should consist of whole grains with 20-30% consisting of vegetables and 5-10% consisting of legumes. Food lists exist for the macrobiotic diet that encourage both frequent and occasional consumption of specific whole foods, as well as ones that ought to be avoided, such as nightshade vegetables and highly processed grains [33]. Pickled and fermented vegetables are allowed and constitute a large portion of sodium intake alongside sea-derived foods.

Sea vegetables and fish are allowed in moderation (5-10%), with the remainder of animal products being disallowed. The diet is very low in fat and promotes getting fats from whole foods such as nuts, seeds and fish. Refined sugar is banned.

Herbal and sprouted wholegrain tea drinks are a focal point in the macrobiotics diet while all commercially processed beverages are removed. 

Where possible, wholefoods should be organic, seasonal and prepared to ensure optimal nutrition. Supplements are discouraged and there are versions of the diet available for specific types of cancer (however there is no proof that these variations may be beneficial).


The macrobiotic diet and lifestyle offer the following potential benefits:

  • May lower LDL cholesterol and increase HDL cholesterol, therefore lowering heart disease risk [34].

  • May help to lower inflammation.

  • May improve insulin signaling and enhance the gut microbiome in a way that decreases diabetes risk [35] and improves markers in those with the condition [36].

  • Promotes weight loss and longevity through caloric restriction.

  • Can help to reduce high blood pressure.


A few concerns regarding this diet have been highlighted in scientific literature, including:

  • Adherence may be low.

  • Some have claimed that this diet may be able to treat, cure or prevent cancer. These claims have no scientific validation [37].

  • This diet is prone to causing nutritional deficiencies, as evidenced by a few studies conducted on children following the diet who had reduced bone mineral density compared to controls. The very high fiber content may interfere with the absorption of calcium, iron, magnesium and zinc. Those on the diet are seen to be low in these nutrients as well as vitamin B12 and Vitamin D. 

  • Grains are known to contain high levels of anti-nutrients and may increase gut inflammation in those with digestive problems.

  • The diet is slightly higher in sodium and lower in potassium than the suggested Recommended Daily Allowance. Thus, it may be contraindicated for those with hypertension and kidney disease.

  • May be too low in healthy fats.

Plant-Based Diets

A bigger emphasis on plant-based foods appears in most top rated diet plans, and diets higher in a healthy variety of plant-based foods have been associated with better long-term health outcomes.

Excluding or restricting the dietary intake of animal products is associated with a few general advantages that appear independent of the ratio of macro nutrients consumed [38]. These include a better cholesterol and lipid profile, as well as increased longevity. Disadvantages include risks of B vitamin deficiency, particularly with regard to vitamin B12. 

In spite of the hype, plant-based diets may still be pursued in an unhealthy manner through over-consumption of refined foods associated with increased disease risk. 

22. Vegetarian

A strictly vegetarian diet is a diet plan that opts for avoiding animal products, only allowing for plant-based foods to be consumed. This is the only requirement for following a vegetarian diet and as such, many healthy diet plans can be modified to become vegetarian.

An ovo-lacto vegetarian diet is a less strict version of vegetarianism in which a person may still opt for a limited intake of eggs and/or dairy products. 

Someone following a vegetarian diet is not necessarily doing so in order to promote the rights of animals; denoting one of the main differences between a vegetarian and vegan individual. 


A vegetarian diet can enhance health and well-being in a number of ways:

  • Helps to lower the risk of Diabetes type 2, hypertension, stroke and coronary artery disease.

  • May lower inflammation and reduce the risk for certain cancers due to the elimination of meat. [39][40]   

  • Enhances overall nutritional status and is generally associated with a higher diet quality [41] than the average Western diet.

  • Improves HDL cholesterol, lowers LDL cholesterol, and promotes a healthy BMI as well as weight loss in some overweight individuals.

  • Is associated with a reduced risk of all-cause mortality and improved longevity.


Vegetarian diets tend to succumb to the following pitfalls:

  • There are no dietary guidelines to follow when on a vegetarian diet, making it easy to follow in an unhealthy manner.

  • Unbalanced vegetarian diets can cause severe nutritional deficiencies, especially in omega-3 fats, vitamin B12, Vitamin D, calcium, iron and zinc.

  • Evidence does not support the notion that consuming a vegetarian diet improves health outcomes more than nutritionally balanced, non-vegetarian diet plans. [42]

  • Vegetarian diets tend to be low in iodine and high in goitrogenic foods like soy that impair iodine uptake. Lacto vegetarians may have an improved iodine status due to the iodine content of good quality dairy products. [43]  

  • Grains and legumes are main sources of vegetarian protein however they are also abundant in anti-nutrients that lower nutrient absorption and increase the risk of deficiencies.

23. Vegan

A vegan diet is a plant-based diet plan that excludes all animal-based foods and is generally perceived as being stricter than a vegetarian diet. 

The vegan diet is promoted as the most ethical diet plan and is strictly adhered to by enthusiasts in an attempt to reduce animal cruelty and in some cases, to promote environmental sustainability. Some individuals following a vegan diet may also avoid honey and other bee products in line with these vegan principles. It is also a common vegan trend to exclude cosmetic products and any other items that were made using animal products.


The vegan diet shares many of the same advantages of a vegetarian diet with greater results. These include:

  • A potentially reduced risk of hypertension, diabetes and obesity.

  • Increased protection against cardiovascular disease mortality due to a better lipid and cholesterol profile.

  • Higher weight loss than a vegetarian diet on average, being associated with a slimmer profile in the long run. [44]

  • May help to lower anxiety, stress and low moods status.

  • An improved gut microbiome profile consisting of less pathogenic strains of bacteria compared to vegetarians or omnivores. [45]

  • Associated with a better risk reduction for breast and prostate cancer compared to other plant-based diets. [46]


A vegan diet also poses similar, yet more severe disadvantages to that of a vegetarian diet, such as:

  • Being associated with greater deficiencies in calcium and vitamin B12 than a vegetarian diet, alongside other nutritional deficiencies associated with vegetarianism. [47]

  • Excludes vegetarian foods that may be beneficial to include in one’s diet such as honey.

  • The diet is very low in saturated fats and may therefore drop cholesterol levels too low. 

  • Many vegan diets place a greater emphasis on consuming raw foods which may pose similar drawbacks to that of a raw food diet.

  • May increase the risk of bone fractures, anemia [48] and atherosclerosis (due to hyperhomocysteinemia) [49].

24. Flexitarian

The Flexitarian Diet is a very popular type of plant-based dietary approach that aims to reduce animal product consumption. Meat and other animal products are regarded as a rich source of many nutrients which ought not to be completely omitted but also ought not to be the main focus of the diet. Sometimes referred to as the semi-vegetarian diet or flexible vegetarian diet, the flexitarian diet is regarded as a vegetarian diet in which the participant can be flexible with their animal product intake. 

There are many approaches to the flexitarian diet with varying meat reduction guidelines. A common approach is to stagger meat reduction into three phases. In the first phase, meat is cut down to 28 ounces per week and consumed only on 5 days. In phase 2 it is cut down to 18 ounces over 3-4 days of the week and in phase 3, one consumes up to 9 ounces over two days of the week.[50]   

Many who adopt a flexitarian diet focus on increasing their intake of highly nutritious plant-based foods. A 13 year study revealed that many flexitarians tend to become full vegetarians after being on a flexitarian diet for a long period of time. [51] 


Advantages of a flexitarian diet tend to reflect those of other vegetarian diets in lesser increments [52]. They include:

  • Encourages optimal weight and BMI.

  • Promotes lower blood glucose levels in the long-term than seen on a non-vegetarian diet.

  • Reduces diabetes and cardiovascular disease risk better than an ovo-lacto vegetarian diet.

  • Tends to provide a better omega-3 status than vegan or vegetarian diets.

  • May help lower frequency of digestive symptoms seen in IBS.

  • Improved gut health due to increased fiber and nutrient intake.

  • Easier to adhere to for some than a strict vegetarian or vegan diet.

  • Can be easily incorporated into other eating plans such as the Mediterranean Diet.


The following pitfalls are associated with a flexitarian diet:

  • Those following this diet are still at an increased risk of anemia and B12 deficiency, however less so than vegan and vegetarian individuals.

  • Without a flexitarian consensus, there is limited scientific evidence to support a standard type of flexitarian diet, with results being proven for variations on meat reduction.

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