Chapter 8: Popular Diets and Health

By Farshad Fani Marvasti, MD, MPH

Student contributor: Diego Quezada

Introduction

Diet is a primary risk factor for chronic disease, and diet-sensitive disease is a major contributor to global health-care costs. Culinary medicine promotes a healthy eating pattern and a nourishing relationship with food that respects the different roles of foods in people’s lives rather than a particular diet per se. Literally thousands of “diets” have been proposed, which can be loosely described as belief-based, food-specific, or nutrient-based; focused on weight loss or weight (muscle) gain; detoxification (detox) diets, and diets designed for specific medical reasons.

“Fad diets” are diets popular for a time without necessarily being based on a standard dietary recommendation. They often promote unreasonably fast weight loss or nonsensical health claims and are advertised to require little effort on the part of the adherent. The promise of easy gains, combined with societal pressure to achieve a certain body type, can leave the public susceptible to unfounded or exaggerated claims. Billions of dollars are spent by consumers each year on ineffective and potentially risky fad diets and diet-related products.

In contrast, some evidence-based diets have emerged as reasonably robust, effective interventions for specific medical reasons. The diets most effective for disease prevention share similar characteristics: they encourage more intake of fruits, vegetables, and whole grains and generally discourage highly processed foods that are higher in sodium and added sugars.

In any case, dietary interventions (like any intervention for medical reasons) should be undertaken with the advice and supervision of a health-care professional, in conjunction with a registered dietitian. These health-care professionals can provide a personalized approach to find the best eating plan for the patient.

Overview of Popular Diets and Health

Chronic disease is responsible for more deaths worldwide than acute infectious conditions.¹ These major chronic conditions include cardiovascular disease (CVD; the number 1 killer globally), cancer, diabetes (>95% being type 2 diabetes), obesity, and noninfectious airway diseases (e.g., asthma, chronic obstructive pulmonary disease).

When examining the diseases of our time, it is evident that diet plays a key role. Diet is the number 1 risk factor for premature, preventable disease and death worldwide.² In the United States, diet has consistently been identified as the top risk factor for premature, preventable death and as a top risk factor for disability-adjusted life-years (DALYs; years affected by disease limiting full function and the ability to live a full life).³

Despite the importance of diet in contributing to human health, there is very little to no nutrition education in medical schools.⁴ Medical students in the United States receive an average of 19.6 hours of nutrition education across all 4 years of medical school.⁵ In addition to the gap of nutrition content in medical education, there is a need for more collaboration and interprofessional care involving medical doctors and registered dietitians. The persistence of this gap in training and interprofessional care has created a void in which popular diets have emerged to influence eating behavior of individuals and communities. Many people excitedly support their chosen popular diet. The goal of this chapter is to compare and evaluate the pros and cons of popular diets, based on the latest scientific evidence. In this chapter, we discuss several popular diets.

Before delving into each of these diets, it is important to know some key findings regarding the role of diet as a primary risk factor for premature disease and death. For example, in the case of CVD, studies have shown that close to half (45.4%) of cardiometabolic deaths were connected directly with diet.⁶ These studies found that the main contributors to this risk were a lack of healthy fats and proteins in the form of nuts, seeds, and fatty fish, as well as an excess amount of sodium.⁶

Additionally, a study of international data from 195 countries, assembled from studies over the course of nearly 20 years, showed that suboptimal diet is responsible for more deaths than any other risks globally (including tobacco smoking), which highlights the urgent need to improve diet around the world.² The same researchers also found that improvement of diet could potentially prevent 1 in every 5 deaths globally and that, unlike other risk factors, diet affected health outcomes regardless of sociodemographic development or age. Less than optimal intake of 3 dietary components (whole grains, fruits, and sodium) accounted for more than 50% of all deaths and 66% of DALYs attributed to diet.²

The Standard American Diet (SAD) is illustrative of the role that diet plays in the development of chronic disease. The SAD dietary pattern has been exported worldwide, which can account for the findings from the aforementioned 195-country study discussed above. Figure 8.1 shows the breakdown of this typical diet consumed in the United States.

As seen in Figure 8.1, the SAD consists of more than 60% of calories coming from highly processed foods. Processed foods are most broadly defined as any raw commodity that is altered from its raw or natural state. Processed foods can be minimally processed (e.g., a bag of frozen vegetables), which is not concerning for health, or more processed, which usually involves adding more ingredients and transforming the food into a product with additional chemical preservatives and flavor enhancers, which can be of concern. Emerging research is showing a strong connection between highly processed or ultra-processed foods and poorer health outcomes, including an increased risk for several cancers, diabetes, obesity, and CVDs.⁷

Some of the characteristics of these highly processed foods include more refined macronutrients, such as carbohydrates in the form of simple sugars without fiber or other nutrients. These same processed foods also have unhealthy forms of fat and excessive amounts of sodium. It is no surprise that processed food makes up greater than 60% of the SAD.

In addition to this diet being the most common diet consumed in the United States, the global expansion of this characteristic Western diet has had a negative impact on physical and mental health around the world.⁸ Given the components of the SAD, anyone who embarks on 1 of the popular diets discussed in this chapter will experience some health benefits. Studies have shown that when people begin keeping track of the food they eat by using an app or as requested by a health-care professional, the quality of food choices improves.⁹ In the case of the popular diets outlined in this chapter, any change from the SAD toward less-processed foods and more thoughtful consideration of food choices will result in some benefits. As we review each of the diets, we will consider how each has benefits as well as potential drawbacks based on the scientific evidence that has been developed to date.

Low-Carbohydrate Diets

A low-carbohydrate (low-carb) diet is an eating pattern that restricts the intake of carbohydrates, typically replacing them with higher amounts of protein and fat. The ketogenic diet is a form of a low-carb diet that is high in fat relative to protein and carbohydrate intake. The macronutrient breakdown for a ketogenic diet is 70% fat, 20% protein, and 10% carbohydrate.

The goal with ketogenic diet is to induce ketosis, a metabolic state that occurs when a body burns fat for energy instead of glucose, which induces weight loss. Ketosis is evidenced by ketones in the blood that can be measured by a finger stick, much like glucometers measure glucose levels. Other low-carb diets include the Atkins diet, which is a bit less clear on the breakdown, with 55% to 65% fat, 20% to 30% protein, and 10% to 15% carbohydrate.

One of the key issues to consider with any form of a lower-carbohydrate diet that generally limits carbohydrates to less than 20% of total calories is the quality of the calories. For example, protein and fat can be sourced from processed meats and inflammatory fat sources, such as lunch meats or vegetable oils, respectively. Or these macronutrients can be sourced from healthy fat sources, such as extra virgin olive oil that is high in monounsaturated fats or lean, unprocessed, grass-fed meats (without added hormones or antibiotics).

The source of the higher amounts of protein and fat can affect the potential health benefits associated with it. For example, processed meats have been identified as a carcinogen associated with colorectal cancer,¹⁰ and fats such as hydrogenated oils found in processed foods may increase shelf life while also increasing the risk of inflammation leading to atherosclerosis and other chronic diseases.¹¹ The pros of a low-carb diet include:

• Weight loss and body composition
• Several studies have shown that low-carb diets can lead to greater weight loss compared with low-fat diets.¹²
• Low-carbohydrate diets may promote greater fat loss and preservation of lean muscle mass, which is important for metabolic health.¹³
• Low-carbohydrate diets may also lead to reduced hunger and increased satiety, potentially aiding in adherence to the diet.¹⁴
• Blood sugar control and insulin sensitivity
• Low-carbohydrate diets improve blood sugar control and insulin sensitivity in individuals with type 2 diabetes.¹⁵
• They may lead to lower fasting blood glucose levels and reduced insulin requirements.¹⁵
• Low-carbohydrate diets may also be beneficial for individuals with insulin resistance or metabolic syndrome.¹⁵
• Cardiovascular risk factors
• Some study findings suggest that low-carb diets can improve cardiovascular risk factors, such as reducing triglyceride levels and increasing high-density lipoprotein cholesterol levels.¹⁶
• They may also lead to greater reductions in blood pressure compared with low-fat diets. However, the long-term effects on cardiovascular health are still debated and require further research.¹⁶

And the cons of a low-carb diet include:

• Nutrient deficiencies
• Restricting carbohydrates may lead to inadequate intake of certain nutrients, such as fiber, vitamins, and minerals.¹⁴ It is important to carefully plan a low-carb diet to ensure adequate nutrient intake and consider supplementation if necessary.¹⁴
• Sustainability and adherence
• Low-carbohydrate diets may be challenging to sustain in the long term due to their restrictive nature and potential social limitations. Adherence to a low-carb diet may also be difficult for individuals who enjoy carbohydrate-rich foods or have cultural dietary preferences.¹⁴
• Potential health risks
• Some studies suggest that long-term adherence (at least 1 year) to low-carb diets may be associated with an increased risk of CVDs and overall mortality.¹⁷ It is important to consider the quality of the food choices within a low-carb diet, because high intake of processed meats and saturated fats may increase health risks.¹⁷

It is crucial to note that the effects of a low-carb diet may vary among individuals, and it is advisable to consult with a health-care professional or registered dietitian before starting any dietary regimen, especially for individuals with specific health conditions or concerns.

 

The Ketogenic Diet: A Form of Low-Carb Diet

As noted, the ketogenic diet is a high-fat, low-carbohydrate, and moderate-protein diet that has gained popularity for its potential health benefits. The primary goal of the ketogenic diet is to restrict carbohydrate intake to a level that triggers ketosis. Typically, this involves consuming less than 50 g of carbohydrates per day, although individual requirements may vary. Instead, the diet emphasizes consuming high amounts of healthy fats found in sources such as avocados, nuts, seeds, and oils, along with moderate protein from sources such as meat, fish, and dairy products.

The same potential challenges associated with low-carb diets may apply to ketogenic diets. Here is brief list of potential health benefits as supported by scientific literature:

• Epilepsy management: The ketogenic diet has been used as a therapeutic approach for drug-resistant epilepsy, particularly in children. Multiple studies have shown its effectiveness in reducing seizure frequency and improving seizure control.¹⁸
• Weight loss: A systematic review and meta-analysis of randomized controlled trials found that the ketogenic diet was more effective for short-term weight loss compared with low-fat diets.¹⁴
• Improved insulin sensitivity: Research suggests the ketogenic diet may improve insulin sensitivity and glycemic control, making it beneficial for individuals with type 2 diabetes or prediabetes.¹⁹
• Neurological disorders: Emerging evidence suggests the ketogenic diet may have potential benefits for various neurological disorders, including Alzheimer’s disease, Parkinson’s disease, and traumatic brain injury. However, more research is needed to establish its efficacy and mechanisms of action.²⁰

It is important to note that the ketogenic diet may not be suitable for everyone. Anyone considering making dietary changes should consult with a health-care professional before starting any changes, especially individuals with certain medical conditions (e.g., risk of osteoporosis, digestive disorders, breastfeeding or pregnant people) or those taking medications.

The following is a list of potential cons of a ketogenic diet:

• The ketogenic diet is very low in carbohydrates, which may lead to nutrient deficiencies if not carefully planned and monitored.¹⁴ Less carbohydrate intake leads to less fiber intake, which is the primary food source for the microbiome, so the lack of fiber in carbohydrate-rich foods (e.g., vegetables, fruits) can be a potential hazard for this popular diet.
• A ketogenic diet can cause side effects such as constipation, bad breath, and nutrient imbalances.¹⁴
• The long-term effects of the ketogenic diet on overall health and disease prevention are still not well understood, and more research is needed.²⁰

 

Paleo Diet

The Paleo diet, also known as the Paleolithic diet or caveman diet, is a dietary approach that aims to mimic the eating habits of our ancient ancestors from the Paleolithic era. It emphasizes consuming whole, unprocessed foods that would have been available to early humans, such as lean meats, fish, fruits, vegetables, nuts, and seeds, and excluding grains, legumes, dairy products, processed foods, and added sugars.

Although the Paleo diet has gained popularity, it is important to note that scientific evidence supporting its specific health benefits is limited. However, some studies have explored selected health benefits of the Paleo diet. Potential pros of the Paleo diet include:

• Weight loss: A small study comparing the Paleo diet with a standard low-fat diet found that the Paleo diet led to greater weight loss and improvements in waist circumference and blood pressure. However, the study had a small sample size and a short duration.²¹
• Metabolic health: Another study compared the Paleo diet with a standard diabetes diet in individuals with type 2 diabetes and found that the Paleo diet led to greater improvements in glycemic control, triglyceride levels, and blood pressure. However, this study also had a small sample size and a short duration.²¹
• Nutrient composition: The Paleo diet can be nutrient-dense, providing adequate amounts of vitamins, minerals, and antioxidants. However, it may be lower in certain nutrients, such as calcium and vitamin D, due to the exclusion of dairy products.²²

It is important to consider that the Paleo diet may not be suitable for everyone, depending on certain medical factors (e.g., risk for osteoporosis, heart, kidney, pancreatic disease), and long-term adherence to the diet may be challenging due to its restrictive nature. Additionally, the evolutionary premise of the diet has been debated because our ancestors’ diets varied significantly depending on geographic location and time period.

 

Plant-Based Diets: Vegetarian and Vegan

Vegetarian Diet

The vegetarian diet is a dietary pattern that excludes the consumption of meat, poultry, and seafood while allowing for the consumption of plant-based foods such as fruits, vegetables, grains, legumes, nuts, and seeds. There are different variations of vegetarian diets, including lacto-vegetarian (includes dairy products), ovo-vegetarian (includes eggs), and lacto-ovo-vegetarian (includes both dairy products and eggs). Scientific research has explored the health effects of vegetarian diets; following are some key findings:

• Cardiovascular health: Several studies have shown that vegetarian diets are associated with a reduced risk of CVDs. A meta-analysis of observational studies found that vegetarians had a 25% lower risk of dying from heart disease compared with nonvegetarians.²³
• Blood pressure control: Research suggests that vegetarian diets may help lower blood pressure. A systematic review and meta-analysis of clinical trials found that vegetarian diets were associated with significant reductions in both systolic and diastolic blood pressures.²⁴
• Diabetes management: Vegetarian diets are beneficial for individuals with type 2 diabetes. A systematic review and meta-analysis of randomized controlled trials found that vegetarian diets led to greater improvements in glycemic control, weight management, and cholesterol levels compared with conventional diets.²⁵
• Cancer prevention: Some studies have suggested that vegetarian diets may be associated with a reduced risk of certain types of cancer, particularly colorectal cancer. However, the evidence is not consistent across all studies, and more research is needed to establish a definitive link.²⁶

It is important to note that vegetarian diets can be nutritionally adequate if well planned to ensure sufficient intake of essential nutrients such as protein, iron, calcium, vitamin B₁₂, and omega-3 fatty acids. Consulting with a health-care professional or registered dietitian is recommended to ensure proper nutrient balance.

Vegan or Plant-Based Diet

The vegan diet is a plant-based dietary pattern that excludes the consumption of all animal products, including meat, poultry, seafood, dairy products, eggs, and honey. It focuses on consuming a variety of plant-based foods, such as fruits, vegetables, grains, legumes, nuts, and seeds. Scientific research has explored the health benefits of vegan diets and shown the benefits are similar to the health benefits of vegetarians diets (see previous section). Beyond this, some research has found additional benefit to being fully plant-based without dairy or eggs including for treating and preventing coronary artery disease,²⁷ cancer risk,²⁸ and longevity.²⁹

It is important to note that although vegan diets can be nutritionally adequate, attention must be given to ensure sufficient intake of essential nutrients such as protein, iron, calcium, vitamin B₁₂, and omega-3 fatty acids. Proper meal planning and potential supplementation may be necessary. Consulting with a health-care professional or registered dietitian is recommended.

Potential cons of plant-cased diets include that certain nutrients, such as vitamin B₁₂ found in red meat, are often deficient in vegetarian diets. Another con to this diet is being a “junk food vegetarian,” whereby meat is avoided and replaced with processed foods, making it less healthy (e.g., chips, french fries, refined grains—all of which are vegetarian). Protein needs may vary per age group. For example, older people have higher protein requirements that require vegetarians in this age group to be mindful of adding more plant-based protein to their diet.

Dietary Approaches to Stop Hypertension Diet

The Dietary Approaches to Stop Hypertension (DASH) diet is a dietary pattern specifically designed to help lower blood pressure and promote overall heart health. It emphasizes consuming a variety of nutrient-rich foods, including fruits, vegetables, whole grains, lean proteins, and low-fat dairy products, and limiting the intake of sodium, saturated fats, and added sugars. Scientific research has demonstrated the effectiveness of the DASH diet in reducing blood pressure and improving cardiovascular health. Some key findings are listed here:

• Blood pressure control: Multiple studies have shown that the DASH diet can significantly lower blood pressure. A systematic review and meta-analysis of randomized controlled trials found that the DASH diet led to significant reductions in both systolic and diastolic blood pressures, particularly in individuals with hypertension.³⁰
• Cardiovascular health: The DASH diet has been associated with a reduced risk of CVDs. A large, prospective cohort study found that adherence to the DASH diet was associated with a lower risk of coronary heart disease and stroke.³¹
• Weight management: The DASH diet can also support weight management. A randomized controlled trial comparing the DASH diet with a control diet found that the DASH diet led to greater weight loss and improvements in body composition.³²
• Nutrient composition: The DASH diet is rich in essential nutrients such as potassium, magnesium, calcium, fiber, and antioxidants. These nutrients have been associated with various health benefits, including blood pressure regulation and cardiovascular health.³³

On the other hand, potential challenges to the DASH diet include adherence, due to the lack of convenience or processed foods and no organized support groups; food-tracking requirement; and limited focus on specific dietary restrictions.

The DASH diet is considered a well-balanced and evidence-based dietary approach for individuals looking to improve their blood pressure and overall heart health. It is important to note that individual variations and specific dietary needs should be considered, and consulting with a health-care professional or registered dietitian is recommended.

Mediterranean Diet

The Mediterranean diet is a dietary pattern inspired by the traditional eating habits of countries bordering the Mediterranean Sea. It is characterized by high consumption of fruits, vegetables, whole grains, legumes, nuts, and olive oil; moderate intake of fish and poultry; and low consumption of red meat, processed foods, and sweets. The health benefits of the Mediterranean diet have been investigated in numerous studies. Some key findings are as follows:

• Cardiovascular health: A critical review of the Mediterranean Diet and Health found that better conformity with the traditional Mediterranean Diet is associated with better cardiovascular health outcomes including clinically significant reductions in coronary artery disease rates, ischemic stroke, and total cardiovascular disease.³⁴
• Diabetes prevention: The Mediterranean diet may help prevent type 2 diabetes. A large randomized controlled trial called PREDIMED (Prevención con Dieta Mediterránea [Prevention with the Mediterranean Diet]) demonstrated that individuals assigned to follow a Mediterranean diet supplemented with extra-virgin olive oil or nuts had a lower incidence of diabetes compared with those following a low-fat diet.³⁵
• Cognitive function: Several studies have indicated that adherence to the Mediterranean diet is associated with better cognitive function and a reduced risk of cognitive decline and Alzheimer’s disease. A systematic review and meta-analysis of observational studies found that higher adherence to the Mediterranean diet was associated with a 33% lower risk of Alzheimer’s disease.³⁶
• Cancer prevention: The Mediterranean diet has been linked to a reduced risk of certain types of cancer, including breast cancer and colorectal cancer. A meta-analysis of observational studies found that higher adherence to the Mediterranean diet was associated with a 10% lower risk of breast cancer.³⁷

Mediterranean-DASH Diet Intervention for Neurodegenerative Delay Diet

The Mediterranean-DASH Diet Intervention for Neurodegenerative Delay (MIND) diet is a dietary pattern specifically designed to promote brain health and reduce the risk of neurodegenerative diseases, such as Alzheimer’s disease. It combines elements of the Mediterranean diet and the DASH diet, focusing on consuming foods that are beneficial for brain health (e.g., fish, berries, nuts, seeds). Although the MIND diet is a relatively new concept, some scientific research has explored its potential benefits, including the following pros and cons:

• Cognitive function: A study found that adherence to the MIND diet was associated with a slower rate of cognitive decline and a reduced risk of Alzheimer’s disease. The study followed older adults over several years and found that those who closely followed the MIND diet had a 53% reduced risk of developing Alzheimer’s disease compared with those who did not adhere to the diet.³⁸
• Neuroprotective effects: The MIND diet emphasizes consuming foods that are rich in nutrients and antioxidants, such as berries, leafy greens, nuts, and olive oil. These components have been associated with neuroprotective effects and may help reduce oxidative stress and inflammation in the brain, which are believed to contribute to neurodegenerative disease.³⁸
• There is the potential for higher amounts of fat and calorie intake and for challenges in adherence for some individuals.
• It may be difficult to translate Mediterranean diet foods across different cultures.

It is important to note that the Mediterranean diet is not a 1-size-fits-all approach, and individual variations and cultural adaptations exist. Additionally, the Mediterranean diet is not solely defined by specific foods but also by the overall dietary pattern and lifestyle factors, such as physical activity and social interactions.

Pescatarian Diet

The pescatarian diet is a dietary pattern that includes plant-based foods along with seafood. It is similar to a vegetarian diet in that it excludes meat and poultry, but it allows for the consumption of fish and other seafood. Scientific research on the pescatarian diet specifically is limited, but studies on similar dietary patterns provide some insights, as follows:

• Cardiovascular health: Several studies have shown that increased fish consumption, which is a key component of the pescatarian diet, is associated with a reduced risk of CVDs. A systematic review and meta-analysis of prospective cohort studies found that greater amounts of fish intake were associated with a lower risk of death from coronary heart disease.³⁹
• Omega-3 fatty acids: Fish is a rich source of omega-3 fatty acids, particularly eicosapentaenoic acid and docosahexaenoic acid. These fatty acids have been associated with various health benefits, including reduced inflammation, improved heart health, and potential cognitive benefits.⁴⁰
• Nutrient intake: The pescatarian diet can provide a range of essential nutrients, including high-quality protein, omega-3 fatty acids, vitamins (such as vitamins D and B₁₂), minerals (e.g., iodine, selenium), and antioxidants. However, attention should be given to ensure a balanced intake of nutrients, especially if other animal products such as dairy and eggs are limited or excluded.

It is important to note that specific dietary needs should be considered when following a pescatarian diet. Additionally, the sustainability and environmental impact of seafood consumption should also be taken into account. For example, consumers can educate themselves on which producers are not overfishing, follow fishery laws, and enact best practices that support marine biodiversity. Identifying community-supported fisheries, buying from trusted retailers and restaurants, and prioritizing US-caught fish (and thereby following US fishing laws) are some of the ways that consumers can consider the environmental impacts of their choices.⁴¹

Anti-Inflammatory Diet

The anti-inflammatory diet is a dietary pattern that focuses on consuming foods that reduce inflammation in the body. Chronic inflammation is associated with various health conditions, including CVDs, diabetes, and certain types of cancer. The anti-inflammatory diet aims to promote overall health and well-being by incorporating foods with anti-inflammatory properties.

Scientific research has identified several key components of the anti-inflammatory diet, including:

• Fruits and vegetables: Numerous studies have shown that fruits and vegetables, particularly those rich in antioxidants and phytochemicals, have anti-inflammatory effects. A systematic review and meta-analysis of observational studies found that higher amounts of fruit and vegetable intake were associated with reduced levels of inflammatory markers.⁴²
• Whole grains: Whole grains, such as whole wheat, brown rice, and oats, are rich in fiber and other nutrients that have been associated with anti-inflammatory effects. Higher whole-grain intake was associated with lower levels of inflammatory markers in a meta-analysis.⁴³
• Healthy fats: The anti-inflammatory diet emphasizes the consumption of healthy fats, such as those found in olive oil, avocados, nuts, and seeds. These foods are rich in monounsaturated and polyunsaturated fats, including omega-3 fatty acids, which have anti-inflammatory properties.⁴⁴
• Fish and seafood: Fatty fish (e.g., salmon, mackerel, sardines) are sources of omega-3 fatty acids, which have been associated with reduced inflammation. A systematic review and meta-analysis of randomized controlled trials found that omega-3 supplementation led to significant reductions in inflammatory markers.⁴⁴

It is important to note that the anti-inflammatory diet is not a specific diet plan but rather a general approach to eating that emphasizes whole, unprocessed foods and limits the consumption of processed foods, refined sugars, and unhealthy fats. Individual variations and specific dietary needs should be considered, and consulting with a health-care professional or registered dietitian is recommended.

Intermittent Fasting

Intermittent fasting (IF) is an eating pattern that involves alternating periods of fasting and eating. Participants usually fast for 14-16 hours or more and then have an eating window of 8-10 hours. For example, one can stop eating at 8 PM and then have their first meal the next morning at 10 AM (a 14-hour fast and a 10-hour eating window, or 14:10) or stop eating at 8 PM and have their first meal at noon (a 16-hour fast and an 8-hour eating window, or 16:8). Here are the pros and cons of IF, supported by scientific references:

• Weight loss and body composition
• Several studies have shown that IF can be an effective approach for weight loss and improving body composition.^45,46
• Intermittent fasting may lead to a reduction in calorie intake and increased fat burning, resulting in weight loss.^46,47
• It may help preserve lean muscle mass during weight loss, which is important for overall health and metabolic rate.⁴⁵
• Insulin sensitivity and blood sugar control
• Intermittent fasting improves insulin sensitivity and blood sugar control, potentially reducing the risk of type 2 diabetes.⁴⁸
• It may lead to lower fasting insulin levels and improved insulin response, which can enhance metabolic health.^45,46
• Cellular repair and longevity
• Findings from studies in animals and some human trials suggest that IF may promote cellular repair processes and increase lifespan.⁴⁹
• It can induce autophagy, a cellular recycling process that removes damaged molecules and organelles, potentially reducing the risk of age-related diseases.⁵⁰
• Adherence and sustainability
• Intermittent fasting may be challenging for some individuals to adhere to in the long term due to the restricted eating windows or extended fasting periods.⁴⁷
• It may not be suitable for individuals with certain medical conditions, such as diabetes or eating disorders, and should be approached with caution.⁴⁷
• Nutrient deficiencies
• Intermittent fasting may increase the risk of nutrient deficiencies if not carefully planned and balanced.⁵⁰
• It is important to ensure adequate intake of essential nutrients, vitamins, and minerals during eating periods to support overall health.⁵¹
• Potential disordered eating patterns
• For some individuals, IF may trigger or exacerbate disordered eating patterns or an unhealthy relationship with food.⁴⁷
• It is crucial to prioritize a balanced and nourishing diet during eating periods and to maintain a healthy mindset toward food and body image.

It is important to note that the effects of IF may vary among individuals, and it is advisable to consult with a health-care professional or registered dietitian before starting any fasting regimen, especially for individuals with specific health conditions or concerns.

 

Table 8.1. Summary of Comparative Analysis of Popular Diets

Diet name	Definition	Pros	Cons
Ketogenic diet	Low-carbohydrate, high-fat diet focused on weight loss	Weight loss, improved insulin sensitivity, potential therapeutic benefits for epilepsy	Nutrient deficiencies, potential adverse effects, limited long-term research
Vegetarian diet	A no-meat diet	Reduced risk of chronic diseases, lower environmental impact, potential weight loss	Nutrient deficiencies, challenges in meeting protein needs, potential reliance on processed foods
Vegan diet	No meat or animal products (e.g., eggs, dairy products)	Reduced risk of chronic diseases, environmental sustainability, potential weight loss	Nutrient deficiencies, challenges in meeting certain nutrient needs, potential social and practical challenges
Mediterranean diet	Based on traditional foods of countries bordering the Mediterranean Sea, including France, Spain, Greece, and Italy	Reduced risk of cardiovascular diseases, improved cognitive function, potential weight loss	Potential higher fat and calorie intake, challenges in adherence for some individuals
Paleo diet	Eating plan based on foods that humans might have eaten during the Paleolithic era	Potential weight loss, improved glucose tolerance, increased nutrient density	Nutrient deficiencies, limited long-term research, potential challenges in meeting dietary recommendations
Dietary Approaches to Stop Hypertension (DASH) diet	A diet to control hypertension rich in fruits, vegetables, whole grains, and low-fat dairy	Lowered blood pressure, reduced risk of cardiovascular diseases, improved overall diet quality	Potential challenges in adherence, limited focus on specific dietary restrictions

In reviewing the popular diets of our time, it is clear that what is popular will continue to change. Unfortunately, it is easy for anyone to get caught up in the hype about any given diet and feel compelled to follow it as the only way to better health. It is our view, as noted in the review of pros and cons for each popular diet, that each of these diets has potential health benefits. Therefore, it is important to work with the patient in terms of which diet they want to try.

Our goal as health-care providers ought to include guidance on the evidence, as outlined in this chapter, to help patients choose wisely and follow the healthiest version of whichever popular diet they want to consider. Knowing the potential benefits of each diet and the particular health conditions and risk factors for each patient will help in determining the right diet for each person. Additionally, it is also important to recognize what the patient’s particular health goals are so evidence can be provided to support the right diet to achieve their specific goals.

Overall, it is important to communicate with patients about the 2020-2025 Dietary Guidelines for Americans, which are the high-level dietary pattern recommendations.⁵² The similarities of many of the popular diets included in this chapter include increased intake of fruits, vegetables, whole grains, nuts, seeds, legumes, healthy fats, dairy products, and fish protein, some of which are reviewed in Table 8.2.

At their best, all the diets presented in this chapter encourage decreased consumption of processed foods in the healthiest versions of them, whether these are processed plant- or animal-based food sources. Health professionals must ensure they understand a patient’s current eating habits and consider making a few key recommendations to improve their overall dietary pattern.⁵³ A few tangible recommendations can be more effective than prescribing a very specific or specialized diet, which may feel overwhelming or unnecessarily complex to a patient.

Table 8.2. Comparison of Food Recommendations for Mediterranean, Vegetarian, and DASH Eating Patterns⁵⁰

Foods	Mediterranean	Vegetarian	DASH
Vegetables	2.5 c/d	2.5 c/d	4-5 servings/d
Fruit	2 c/d	2 c/d	4-5 servings/d
Grains	6 oz/d of whole grains	6 oz/d of whole grains	6-8 servings/d
Dairy	2 c/d	3 c/d	2-3 servings, specifically low-fat
Nuts, seeds, legumes	5 oz/wk	1-2 c/d	2-3 servings/d
Fats and oils	27 g (2 tbsp)/d; extra-virgin olive oil is the preferred source	3 c/wk of legumes; 14 oz/wk of seeds and nuts	2-3 servings/d
Meats, poultry, eggs, fish	6.5 oz/d fish/seafood; 15 oz/wk of meat poultry; 26 oz/wk of eggs	3.5 oz/d; 3.5 oz/wk of eggs	6 oz/d
Sweets and sugars	>13% of calories (260 calories) from sugars, solid fats, added refined starches, and alcohol	>15% of calories (290 calories) from sugars, solid fats, added refined starches, and alcohol	≤5 servings/wk
Sodium	Less added salt; use of herbs and spices encouraged		>2,300 mg or <1,500 mg for those with high blood pressure
Alcohol	Mainly wine during meals		<2 drinks/d for men; <1 drink/d for women
Water	6-8 c/d
Abbreviations: c = cup; d = day; g = gram; mg = milligram; oz = ounce; tbsp = tablespoon; wk = week.

Health professionals should make recommendations that promote small, gradual changes and feel realistic and tangible to patients. Examples might be trying 1 meatless meal a week, or adding a fruit as a snack each day.⁵² Health professionals should also focus on the quality of foods eaten and encourage increased consumption of whole foods, fruits, vegetables, and whole grains as much as possible (vs processed or packaged foods that may still fit a specific Paleo or vegan diet plan).⁵³

When making recommendations, it is important to consider individuals’ needs, sociocultural, and socioeconomic factors. Please see chapter 12 for more information on how to incorporate these considerations into patient recommendations, which will support adherence and long-term adoption success.⁵²

In conclusion, it is important to continue researching dietary patterns and health while keeping an open mind to new ideas about eating. It’s important to realize that these diets are still in dire need of research of long-term effects and responses to each specific popular diet that surfaces through social media. To identify the most accurate methods of assessing individual dietary patterns as well as their outcomes, short- and long-term research is necessary. Additionally, it is important to ensure that dietary advice or food prescriptions are practical and personalized, to be a key part of patients’ success.

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