Benefits of Plant-Based Diets in Athletic Performance

This article was originally published in our Spring 2021 print issue.

Today, there are several elite athletes who successfully compete and win while eating a plant-based diet. From tennis player Venus Williams to basketball player Kyrie Irving to ultramarathoner Scott Jurek, athletes who compete at high levels in different sports proudly support and talk about the importance of their plant-based diets.   Because of these correlations, researchers in recent years have been studying how nutrition plays a role in optimizing athletic performance.  Researchers want to know if these athletes have better results in performance because of their plant-based diets, and if so, how these diets actually improve athletic performance.  Recent research shows that plant-based diets can help athletes improve their performance by decreasing weight, creating leaner bodies, and improving stamina.  While better performance is not dependent on a complete plant-based diet and can also be achieved by  eating meat products, athletes who particularly require weight restrictions, speed, and endurance should consider the benefits of plant-based diets. 

Several research studies have shown that plant-based diets reduce body fat. One clinical study by Barnard et. al researched the effects of a plant-based diet  in postemenopausal women after 14 weeks.  From this study, it was reported that the adoption of a plant-based diet had a statistically significant mean weight loss of 5.8 kg  compared to a weight loss of 3.8 kg in the control group which adopted a meat-inclusive diet following the National Cholesterol Education Program guidelines.  One could argue that perhaps the women who had the plant-based diets ate less food than the individuals who were on a diet plan that included meat.  Looking further into the study, the women had no absolute limit to the amount of food they could eat, and both the intervention  and  control groups had similar caloric intakes throughout the study.  While Barnard’s study was done in postmenopausal women to control for hormonal changes that occur in pre-menopausal women, other studies using different populations have also showed similar results. For example, a randomized study by Wright et. al found that male and female participants aged 35-70 who followed a plant-based diet had a significant reduction in mean BMI (body mass index) compared to the control group of participants who did not use a plant-based diet, a 4.4 BMI point reduction versus 0.4 point reduction respectively.  Plant-based diets not only reduce an individual’s weight and BMI scores, but they also are associated with overall leaner bodies, which can be measured by adiposity throughout one’s body. In a large, prospective, population-based study performed in the Netherlands over a period of seven years, researchers found that a greater adherence to a plant-based diet resulted in a statistically significant decrease in BMI as well as a statistically significant decrease in waist circumference, fat mass index, and body fat percentage. For the study’s analysis, the researchers stratified 9,633 individuals into quintiles according to  how plant-based their diets were.  Findings highlighted that the higher the quintile – or the more plant-based the individuals’ diets were – the greater the change in BMI, waist circumference, fat mass index, and body fat percentage over time. One potential counterargument could be that individuals who ate less meat were individuals who naturally led healthier lifestyles.  In order to try and address such variables, the authors built two models that assessed for confounders, including lifestyle behaviors like smoking status and physical activity.  The article did show that individuals with more plant-based diets were more educated and exercised more overall, which could contribute to the findings.  Nevertheless, as the research suggests, even a relative decrease in meat-based foods and increase in plant-based foods can help decrease body fat composition, and thus leaner body mass.

Leaner body mass is desirable for improved athletic performance.  One of the first published studies of the body composition of U.S. Olympians showed that they had lower body fat percentage and higher lean body mass compared to college athletes.  More recent studies have been conducted to examine the body composition of elite athletes.  In several studies of collegiate athletes, body fat percentage and lean body mass differed across different sports, but athletes still had less overall body fat percentage than other college students.  A weakness of these studies is that they did not show specifically a causation between leaner bodies and athletic performance; these studies did not prove whether leaner bodies result in better athletic performance, or if elite athletes spend more time and energy practicing and thus have leaner bodies.   However, the fact that these athletes are collegiate athletes and Olympians implies that these are some of the most elite athletes in their respective sports, and at the very least, that leaner bodies are  desirable for top athletic performance. Other national sports organizations also discuss the benefits of achieving greater lean body mass.  For example, the National Strength and Conditioning Association states that athletes who compete in weight classes, such as boxers and weightlifters, benefit from leaner bodies because they can improve strength and power while maintaining their weight classes.  Other than making the cut for weight classes, “body weight can influence an athlete’s speed, endurance, and power… and body composition can affect an athlete’s strength, agility and appearance.” The Nutrition and Performance position paper written by the American College of Sports Medicine recognizes that measuring ideal body fat composition depends on age, gender, sex, and sport of an individual athlete. But, the position paper does mention that the United States Olympic Committee uses the sum of seven skinfolds (measured in mm) as a standard for measuring percentage of body fat, and suggests “the range of values for the athletic population is 30-60 mm for males and 40-90mm for females” if you use the sum of seven skinfolds measurement as a guideline for elite athletes and their coaches.  

One can argue that there are several other ways to reduce body fat percentage other than plant-based diets.  Human physiology shows that body fat increases because our bodies store extra calories.  As stated in the Harvard Medical School’s Website, “excess calories are stored throughout your body as fat. Your body stores this fat within specialized fat cells (adipose tissue).”  If this is the case, then athletes can also decrease their body fat percentage through other methods of decreasing calories, such as other diets.  For example, a recent large study DIETFITS (Diet Intervention Examining the Factors Interacting with Treatment Success) concluded that both low-fat and low-carb diets were successful in weight loss.  Similarly, studies also show significant reduction in weight, BMI and waist circumference when individuals used the Italian Mediterranean Diet and Paleolithic Diet, which both include animal products.  However, several meats are unhealthy and are loaded with saturated fat, making it more likely for individuals to gain weight given a similar intake of food. That’s because fat has more than twice the amount of calories per gram compared to carbohydrates and proteins.  In other words, eating 1 gram of red meat will have a greater percentage of fat, and thus contain more than twice as many calories than if you ate 1 gram of vegetables. If an individual were to eat an equal number of plant-based calories versus meat-based calories, the individual can eat twice as much vegetables than red meat.

While some athletes make it a goal to decrease body fat percentage, it is important for athletes to also get enough calories in order to optimize their athletic performance.  Since athletes are doing more physical activity each day than the average person, they also need to consume more calories to match their energy expenditure.  As Dr. Theodore Shybut at the Baylor College of Medicine explained, “for an average person, the daily caloric intake might be 1,800 to 2,000 calories. An athlete who is a competitive heavyweight rower or training for long distance running races, for example, may need to eat two or three times that amount of calories daily.”  It’s important to note that athletes need to consume the right kind of calories, and the foods that athletes consume determine that types of calories his or her body receives.  Not all calories are the same.

Carbohydrates are important sources of our body’s energy and are necessary for athletes.  Carbohydrates are either broken down into glucose, which our body can quickly use as energy , or stored in our bodies as glycogen, which can be used as energy once all the glucose is consumed.  A review article by Murray and Rosenbloom stated, “a high-carbohydrate diet remains the evidence-based recommendation for athletes who engage in hours of physical activity on a daily basis.”  There are two types of carbohydrates.The first is a simple carbohydrate which naturally occurs in small amounts in sweet foods like fruits. These are more commonly consumed by people through sugar, fruit juice concentrate, soda, and several other processed foodsThe second type is a complex carbohydrate found in whole grain foods, fruits, and starchy vegetables. 

Complex carbohydrates, and not simple carbohydrates, are important for enhanced athletic performance, particularly for endurance training lasting more than 90-minutes.  First, because simple carbohydrates are often digested more easily and quickly, individuals experience a “sugar rush,” which provides the body with an immediate but short-lasting source of energy.  Because competitive athletes practice for multiple hours per day, it is important for them to have a constant supply of energy rather than having short energy spikes.  Thus, plant-based diets are beneficial because they contain a significant portion of complex carbohydrates and will help athletes have a longer, more stable, and more constant supply of energy throughout the day.  Second, complex carbohydrates are important for glycogen storage.  Glycogen synthesis is a slow process, taking hours to days to replete glycogen storages after an intense workout.   In fact, Murray and Rosenbloom summarized, “if daily carbohydrate intake is insufficient to fully replace the glycogen metabolized during hard labor or training, muscle glycogen concentration in active muscles will fall progressively over a period of days.”  In order to maintain glycogen stores, athletes need to consume a high-carbohydrate diet that contains complex carbohydrates so that there is a longer-lasting supply of carbohydrates that will be available for on-going glycogen repletion.

Recently, competitive athletes have been promoting high-fat diets contributing to their elite performance.   Some individuals misconceive that eating a high-fat diet leads to high levels of fat stores, which can be utilized for long-distance efforts or endurance sports.  However, as mentioned earlier, eating fats does not equal increased adipose tissue.   Another hypothesis by sports nutritionists is that athletes are not utilizing fat stores enough. In an article by Volek et. al Rethinking Fat as a Fuel for Endurance Sports, the authors explain the science behind high-fat diets and exercise physiology: “Current fueling tactics that emphasize high-carbohydrate intakes before and during exercise inhibit fat utilization. The most efficient approach to accelerate the body’s ability to oxidize fat is to lower dietary carbohydrate intake to a level that results in nutritional ketosis (i.e., circulating ketone levels >0.5 mmol/L) while increasing fat intake for a period of several weeks.”  However, recent research has proven that high-fat diets do not enhance exercise capacity and performance.  A review article by Hawley and Leckey summarized findings about high-fat diets in existing literatures.  First, biochemistry research found that endurance events lasting up to 3 hours depend on carbohydrate-based energy sources, like glucose and glycogen, rather than fat.  Second, it was found that high-fat, low-carb diets in fact do not bypass glycogen stores to tap into fat stores nor do they improve training capacity or endurance.  Finally, high-fat, low-carb diets are actually found to be detrimental to athletic training because they impair normal energy breakdown pathways and limit energy in the form of “high-intensity ATP production.”  Given this evidence, athletes should aim to have enough glucose and glycogen stores in their bodies, and plant-based diets are helpful in achieving those goals. 

Nutrition is an important factor that helps athletes reach peak athletic performance.  Other behavioral health factors that are important include muscle strengthening, endurance training, sleep, and mental health.  Research studies have found that plant-based diets are effective in decreasing weight, creating leaner bodies through decreases in body fat percentage, and enhancing athletic endurance.  However, there is still a lot of research that needs to be conducted to further clarify  the specific beneficial effects of plant-based diets on athletic performance. For example, researchers can look at the effect of plant-based diet on individual sports.  Or, researchers can conduct studies to see if plant-based diets impact competition results, such as athletes’ times during track competitions.  Different individuals may seek out different benefits from plant-based diets; some individuals may desire to have leaner bodies while others may desire to increase stamina.  However, for athletes who are trying to gain a competitive edge on all aspects of health that contribute to their performance, they should at least consider trying a plant-based diet because of its potential benefits.