The Benefits of Plant-Based Nutrition: Obesity & Weight Management

Individuals consuming more plant-based diets have lower rates of overweight and obesity than those whose diets include or emphasize meat and refined foods.

Abstract

Individuals consuming more plant-based diets have lower rates of overweight and obesity than those whose diets include or emphasize meat and refined foods.1–4 Plant-based patterns are lower in fat and cholesterol and promote both weight loss and long-term healthy weight maintenance.5 Fiber and water in whole plant foods promote satiety with lower caloric density more than animal-based foods, thus allowing the body to reach its natural weight setpoint without deprivation.5, 6

Obesity is a complex disease state involving excessive adipose tissue.7 Overweight and obesity are prominent risk factors for developing metabolic syndrome, heart disease, diabetes, and certain cancers.8 Findings from large-scale epidemiological studies indicate that plant-based diets lead to healthy weight maintenance and reduce both prevalence and incidence of overweight and obesity.1 The American Medical Association designated obesity a disease in 2013.9 As a result, the idea that obesity is caused by insufficient willpower, lack of discipline, and bad personal choices has transformed the public discourse around the condition and reframed it as a disease that increases other health complications and conditions.

Emerging research on the effects of the obesogenic food environment driven by the addictive qualities of refined sugar, salt, and fat, coupled with prevalent sedentary behavior indicates the importance of considering broader environmental conditions when addressing overweight and obesity.10 Plant-based diets help circumnavigate the built environment by normalizing the taste of healthy food and breaking the pull of these addictive ingredients to allow for a healthy weight.11–13

Table 1 Relationship with amount of weight loss and various conditions76

Mechanisms

Plant-based diets have consistently been associated with reduced body weight because they directly address the primary dietary mechanisms that lead to reduced body fat.92 The mechanisms by which WFPB diets support healthy weight maintenance and weight loss include reduced energy density, increased satiety, avoidance of addictive foods, and positive benefits for the gut microbiota. With obesity, adipose tissue and visceral fat expansion cause compression, joint stress, metabolic disorders, organ dysfunction, and increased mortality.93 The increase in peripheral and central fat mass is a chronic and potentially reversible process. Conversely, the expansion of adipose tissues and visceral fat leads to organ dysfunction and an increased risk of mortality. Such an increased risk of mortality and morbidity can also affect metabolically healthy individuals with obesity with disease progression.13

Energy Density

The mechanisms by which plant-based diets cause weight loss hinge on reduced dietary energy density due to their higher fiber, higher water, lowfat content, and increased postprandial energy expenditure.94, 95 Energy density is the amount of energy in a particular weight of food, in the form of calories per gram, spanning from 0 to 9 kcal/g, along with its water content. Fat is around 9 kcal/g, carbohydrate and protein are both around 4 kcal/g, and alcohol is 7 kcal/g.90 Foods high in calorie density have a large number of calories per unit weight of food, and foods low in calorie density have far fewer calories per unit weight of food.96 Foods low in calorie density with higher fiber content effectively increase satiety, as volume and fiber content activate receptors in the stomach that respond to being physically full of food.97, 98 Thus, eating high-fiber foods (unrefined, plant foods) makes it possible to fill up on fewer calories without experiencing hunger.96 Foods lower in calorie density include whole fruits, colorful vegetables, starchy vegetables, intact whole grains, and legumes. These are also the foods highest in nutrient density. Therefore, by following a diet lower in calorie density, one also consumes a diet highest in nutrient density. In contrast, animal foods and refined foods are energy-dense, making it easier to overconsume calories without a need. Table 2 presents a sample of energy and fiber content of select plant, animal, and highly processed foods, demonstrating that, overall, unrefined plant foods maximize fiber consumption and allow one to eat food with lower energy density.

Fiber

Fiber is found only in plant foods⁹⁹ and is an essential component of a healthy eating pattern, as high fiber consumption is associated with overall lower chronic disease. Higher fiber consumption is a hallmark of plant-based diets,100 and in observational studies, individuals consuming omnivorous diets frequently do not meet fiber recommendations while those consuming increasingly plant-based diets do.^{101, 102} Higher fiber intakes increase satiety, a key component of reduced energy consumption, and higher fiber consumption is implicated in weight loss.¹⁰³ Highly processed foods lacking intact fiber make up the bulk of calories consumed in America,¹⁰⁴ facilitating overconsumption and weight gain. These foods have become progressively cheaper and easier to access in the modern food environment.¹⁰⁴

Gut Microbiota

Microbiome dysbiosis that promotes bile acid fermentation is associated with obesity.⁹² Mechanisms may include impeding the abundance and variety of intestinal flora from excessive intake of unhealthy foods and lack of dietary fiber. The fermentation of fiber appears to be a factor in a host of mechanisms related to obesity, including intestinal barrier function, glucose function, and appetite regulation.¹⁰⁵ Short-chain fatty acids (SCFAs) produced by the gut microbiota through its digestion and fermentation process can modulate satiety and eating patterns, and regulate energy intake through appetite. SCFAs can also suppress intestinal mobility transit and allow for a higher uptake of nutrients.¹⁰⁶

Whole Plant Foods’ Effect on Satiety

Whole food, predominantly plant-based diets, have a number of characteristics that increase satiety, a key element of weight loss. Whole plant foods increase satiety more than highly processed foods lacking intact fiber to hold water and macronutrients in the stomach. Further, solid foods have a greater effect than liquid.¹⁰⁷ Water in food is chemically different from water taken as a beverage as it leaves the stomach more slowly and improves satiety.¹⁰⁸ The fiber in unrefined carbohydrates enhances satiety without adding calories. Fiber-filled foods require greater mastication, which reduces the ingestion rate, increases stomach distention, and promotes satiation. Soluble fibers delay gastric emptying and may be linked to the “second meal effect, delaying the return of hunger.¹⁰⁹ Though protein has demonstrated a higher satiety effect than carbohydrate, trials usually compare a ketogenic-style diet to a conventional American Heart Association diet of 30% fat (which is not very low-fat) to a diet that includes refined and processed low-fat animal foods; whole food diets are not typically included.

Food Addiction and Hyperpalatable Foods

Both food and drug dependency activate similar neural circuitry inducing biochemical change in the brain that can lead to craving beyond need.^110,111 Highly processed foods made of concentrated fat, sugar, and sodium are created to surpass the rewarding properties of whole foods such as fruits and vegetables. They cause the release of neurotransmitters dopamine and opioids expressed throughout the limbic system that can reinforce the eating behaviors driving obesity.⁵¹ Addictive patterns of excessive eating are often attributed to the stimulating properties of these hyperpalatable foods prevalent in our modern food environment. Food addiction research indicates that it may be preferable for some people to avoid certain trigger foods altogether as opposed to eating less of them.¹¹² A WFPB diet may effectively overcome addiction to hyperpalatable foods in individuals with obesity through the avoidance of trigger foods containing added fat, sugar, and salt.

Significant Weight Loss Using a Plant-Based Diet

In 2021, a critical study comparing weight loss between diets demonstrated the unique benefit for overweight individuals of a minimally processed, plant-based, low-fat diet consumed in ad libitum conditions.⁸⁹ Those consuming the low-fat, plant-based diet reduced energy intake by approximately 689 kcal/day, compared to a minimally processed, animal-based, ketogenic, low-carbohydrate diet.⁸⁹ Participants on the minimally processed, animal-based diet lost weight and body fat but reported no significant differences in hunger, fullness, satisfaction, or pleasantness of meals.⁸⁹

The 2017 BROAD study found that a WFPB diet resulted in similar weight loss at 12 months compared to other diets such as low-carbohydrate and low-fat diet, which led to significant BMI and cholesterol improvements and improvements to other risk factors.⁵ Similar studies have observed similar weight loss, which is: at six months 12.0 kg reduction (95% CI±1.8), and at one year 10.9 kg (95% CI±1.2) and 12.2 kg reductions (95% CI±1.3); (this last study included telemonitoring113).⁵ Further, those on the diet had the advantage of eating to satiation without food restriction. In contrast, studies on the effects of low-carbohydrate diets have shown higher rates of all-cause mortality,¹¹⁴ decreased peripheral flow-mediated dilation,¹¹⁵ worsening of coronary artery disease,¹¹⁶ and increased constipation rates, headache, halitosis, muscle cramps, general weakness, and rash.¹¹⁷ Thus, while some evidence exists that low-carbohydrate diets may aid in weight loss, the cardiometabolic side effects are cause for concern, and dietary treatment decisions should be made on an individual basis weighing risks and benefits for the patient, as well as adherence.

Common Questions and Concerns

Don’t carbs make people gain weight?

Though refined carbohydrate products like baked goods are associated with weight gain, increased carbohydrate and fiber intake as part of a plant-based, high-carbohydrate, low-fat diet are associated with beneficial effects on weight, body composition, and insulin resistance.¹⁰³ WFPB diet is primarily composed of complex and unrefined carbohydrates.¹⁰⁰ The healthiest cultures in the world eat a high-carbohydrate diet.¹¹⁸ Carbohydrate quality is important, and complex and unrefined carbohydrates from legumes, vegetables, whole grains, and fruits differ in their health effects from refined carbohydrates found in soda, pastries, cookies, and white bread.¹¹⁹

Doesn’t a low-carbohydrate diet work for weight loss?

Low-carbohydrate diets have produced weight loss in experimental and real-world settings, but the effectiveness is based on energy restriction, not the quality of the diet. Low-carbohydrate diets are typically based on high amounts of animal foods, substituting carbohydrate, the body’s preferred energy source, for fat and protein. The body breaks down protein first and then fat for energy. Low-carbohydrate diets increase LDL cholesterol, which can have long-term cardiovascular effects.89, 120 Substantial reduction of dietary carbohydrate can induce a state of ketosis, which may suppress appetite.

Researchers examining data from The New DIETs study found that non-compliant vegan and vegetarian participants (n=16) were still consuming a more plant-food diet at six months than other groups such as non-adherent pesco-vegetarian/semi-vegetarian (n = 15, −2.3 ± 200.3 mg; P = 0.02) and omnivorous participants (n = 7, 17.0 ± 36.0 mg; P = 0.04).2, 65 Clinicians treating patients on low-carbohydrate diets, such as ketogenic-style diets, should be vigilant in encouraging them to consume healthy whole carbohydrate foods, such as an abundance of non-starchy vegetables, berries and citrus, and those vegetables low in starch but high in resistant starch such as jicama. Some individuals on ketogenic diets have been shown to have reduced exercise tolerance due to higher levels of blood ketones.¹²¹ Further, the long-term effects of the ketogenic diet on the gut microbiota are yet unclear. Physicians supervising patients on a ketogenic diet should consider supplementation with inulin, lactulose, fructooligosaccharides, and galacto-oligosaccharides, to increase the population of Bifidobacterium.⁸⁰

Some research demonstrates greater weight loss among obese subjects on a low-carbohydrate diet compared to a low-fat, plant-based diet, though greater improvements in triglyceride levels and insulin sensitivity have been demonstrated using a low-fat diet of any kind. In a patient-centered decision-making discussion, the physician should weigh the risks and benefits of carbohydrate-restricted diets with the patient, explaining that the ketogenic mechanism ends as soon as individuals stop the diet, often resulting in regaining of weight.¹²² As with any treatment to overcome disease and decrease mortality risk, including bariatric surgery with its risk of ulcers or dumping syndrome, the benefits in any particular situation may outweigh the risks. The risk of relapse with low-carbohydrate diets is the same as with any other diet.

Some people report they have tried a vegetarian diet in that past and felt hungry.

A vegan or vegetarian diet consisting of processed foods and refined grains may not supply enough nutrients, intact fiber, and water to feel satiated. Legumes and whole grains, potatoes, and soybean products like tempeh and tofu may have been lacking, and these foods allow for the feeling of fullness and satiation.¹²³ Potentially addictive foods with saturated fats and refined sugars may make individuals consuming a vegetarian diet that is not a WFPB diet more hungry. A well-planned, plant-based diet has all the nutrients needed for health (except for possibly vitamins B12 and D), including vitamins A, D, E, C, folate, calcium, magnesium, potassium, and fiber.¹²⁴ For most individuals, it takes time for the body to get used to the different macronutrient content (a week or two), particularly if one is used to high-density foods such as cheese and meat. Additionally, when eating a less energy-dense diet, it may be necessary to increase food volume to consume enough calories.

Isn’t weight gain a normal part of aging?

Over the lifespan, metabolism naturally slows down, and body composition gradually shifts—the proportion of muscle decreases, and fat increases. This shift makes it easier to gain weight if calorie intake and activity level stay the same. In addition, some people become less physically active as they age, increasing the risk of weight gain.¹²⁵ For those who continue eating a rich Western diet, weight gain may seem inevitable, but weight gain can be prevented using a high-fiber, plant-based diet and daily physical activity.

No diet has ever worked for me.

Generally, dieting is not associated with long term weight loss. Individuals are challenged by interactions between biology, behavior, and the obesogenic environment.⁵⁷ A dietary plan often leads to feelings of deprivation and restriction, which is hard to maintain. Losing weight using a nutritive plant-based approach as opposed to a calorically restrictive method may allow for long term success, healthier outcomes, and a healthier relationship with food. Further, food deprivation can lead to hormonal imbalances making us more prone to depression, a common state among dieters. Irritability, anger, anxiety, mood swings etc., are typical for dieters. A low-carbohydrate, high protein diet; low-protein, high-carbohydrate diet; and an energy-restricted low-carbohydrate diet have all demonstrated the effect of synthesis and metabolism of tryptophan, serotonin, noradrenaline, and dopamine.^{126, 127} Further, when the body senses calorie restriction, metabolism will slow down to preserve energy and burn fewer calories.^{81, 127} A nutritious, fiber-filled dietary pattern can avoid these pitfalls, as fiber fills the stomach and offers satiety.

I just can’t lose weight from diets.

Though some medical conditions can drive weight gain and prevent weight loss, including hypothyroidism, polycystic ovarian syndrome, and sleep apnea, for most individuals, weight is determined by energy intake vs. energy expenditures (calories in vs. calories out). Energy balance, the relationship between intake and expenditure, is affected by various dietary factors and physical activity behaviors. In the obesogenic modern food environment, it is extremely easy, for reasons previously discussed, to consume more energy than needed. According to a 2014 study, about 19.9% of people in North America and Europe satisfy the criteria for food addiction.¹²⁸ Further, weight loss can be a slow process, and many people have unrealistic expectations. Research indicates that any diet may work with consistent adherence,¹²⁹ but a nutritious plant-based diet may resolve many of these roadblocks related to satisfaction and enjoyment and become a life-long healthy alternative to unhealthy eating patterns.

Download the full 181 page Benefits of Plant-Based Nutrition White Paper for access to all references, key studies and more.

Promising Results—Examples of Disease Reversal

Many people feel demoralized after failing to lose weight and keep it off to control chronic health conditions associated with being overweight. These case reports reflect the relief that many patients experience using a WFPB diet to effectively treat cardiometabolic risk reduction and weight loss. The prescriptive solution to rising obesity prevalence caused by increased convenience and marketing of high-fat, low nutrient food is the use of a high fiber, high carbohydrate dietary protocol, which is both therapeutic and sustainable over the long term. A low-fat, plant-based diet shows the possibility of significant weight loss both in short-term studies, as well as maintaining weight loss over the years.^{81, 138, 139}

54-Year Old Woman Loses 50 Pounds in 6 Months

A 54-year-old female with a grade 3 obesity, BMI of 45.2 kg/m2, and type II diabetes (hemoglobin A1c 8.1%) succeeded in losing 22.7 kg and reversed her diabetes without the use of medications using a WFPB dietary pattern. After suffering from lower extremity edema, her x-Ray revealed lower extremity atherosclerosis. She was started on a beta-blocker, an ACE inhibitor, and a statin. She underwent cardiac catheterization revealing a cardiomyopathy of a 30% proximal left anterior descending artery stenosis, a 25% proximal and a 60% distal left circumflex artery stenosis, and a 65% first obtuse marginal artery lesion.140 Shaken by her diagnosis, she became determined to adopt a healthy WFPB diet. She lost 22.7 kg in <6 months. Her diabetes resolved, with her hemoglobin A1c falling to 5.7% without the use of diabetes medications. Her baseline dyspnea on exertion improved considerably, and a repeat echocardiography in six months revealed a normal left ventricular ejection fraction of 55%.¹⁴⁰

50-Pound Weight Loss and Reversal of Comorbidities in 9 Months

A 65-year-old male diabetic veteran lost 50 pounds after surviving two heart attacks within 62 days and triple bypass surgery. After participating in a Veteran’s Hospital-sponsored Heart Disease Reversal Program, he adopted a WFPB diet under the watch of the program’s doctor. He lost 9 pounds in the first month. At three months he was completely free of his angina, and at 9 months lost 50 pounds, and his diabetes medication was cut in half.¹⁴¹

Conclusion

To date, there is a wealth of data from observational and clinical studies establishing improvements in body weight using a healthy, plant-prominent diet, apparently attributable to reduced dietary energy density and increased postprandial energy expenditure. In addition to weight loss, plant-based diets led to favorable changes in overall nutrition, plasma lipid concentrations, blood glucose, and blood pressure, which lowers risk and, in some cases, reversed chronic comorbidities. In summary, the body of evidence presented here suggests that low-fat, plant-based diets and WFPB diets effectively reduce weight, reduce blood pressure, improve glycemic control, and reduce fat mass among individuals with obesity, as well as prevent weight gain.

Download the full 181 page Benefits of Plant-Based Nutrition White Paper for access to all references, key studies and more.