Improving VO2 Max: A Look at Vegetarian and Vegan Athletes

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Intro: VO2 max—or peak oxygen uptake—is an indicator of aerobic capacity. The higher the rate, the greater potential for athletic endurance. Watch this video to see how vegetarian vs. nonvegetarian diets differ in this capacity.

In my video about comparing vegetarian and vegan athletic performance, endurance, and strength, I discussed a 2020 study that found that vegan athletes—even though they were significantly older—had significantly superior aerobic capacity and endurance, lasting 25 percent longer on a time-to-exhaustion cycling test. The question is: why? One potential mechanism that could explain the greater level of endurance performance in vegans may be a higher amount of carbohydrate intake, which could lead to better endurance performance through higher muscle glycogen storage. Other potential mechanisms that may explain the better endurance performance in vegans could be due to the anti-oxidant and anti-inflammatory profiles of their diet.

Maybe it’s even their hearts. Yet another study showing superior VO2 max in vegan athletes––meaning superior aerobic capacity. This time they also did echocardiograms, looking at their hearts in real-time using ultrasound, and the lower relative wall thickness and better main ventricle systolic and diastolic function in the vegans are most likely positive findings.

Now wait a second; given the higher VO2 max reached by the vegan athletes, maybe they were just better trained than the nonvegan athletes, and that’s why their hearts looked like they were working better. However, the weekly training frequency and running distances were similar in both groups, suggesting benefits even with the same amount of training.

So, it’s important to educate healthcare professionals so they don’t try to discourage a vegan diet, and may even want to consider telling folks implementing an exercise training program to give it a try. But you don’t know if it has the same kinds of effects in nonathletes, until you put it to the test.

A vegetarian vs. conventional calorie-restricted diet: the effect on physical fitness in response to aerobic exercise in patients with type 2 diabetes. Diabetics were randomized to the same caloric restriction, the same exercise, but just vegetarian versus nonvegetarian. They provided all the meals so they could ensure compliance and closely monitor the exercising.

VO2 max increased by 12 percent in the vegetarian group, significantly better than in the nonvegetarian group who didn’t significantly improve at all. Maximal performance increased by 21 percent in the vegetarian group––again, significantly better than in the nonvegetarian group, who didn’t significantly improve at all. In other words, the results indicated that more plant-based diets led more effectively to improvement in physical fitness than less plant-based diets, after the same aerobic exercise program. Here’s what the graphs look like: significantly better power output and aerobic capacity in the group that was randomized to a vegetarian diet.

It seems that those eating vegetarian were able to better burn off carbohydrates compared to nonvegetarians, and had better insulin sensitivity––both markers of improved metabolic flexibility, meaning the ability to switch back and forth between burning sugar and fat.

Besides physiological mechanisms, there may also be psychological factors. They observed reduced hunger and reduced feelings of depression in the vegetarian group, which may have given them a more positive attitude toward exercise. Here’s the psychological data. Those randomized to eat vegetarian had a greater improvement in quality of life and mood. They felt less constrained, meaning the calorie restriction didn’t seem as burdensome; they had less disinhibition, meaning less tendency to binge and overeat, along with maybe less feelings of hunger. Not to mention the superior effects of a vegetarian diet on body weight, glycemic control, blood lipids, insulin sensitivity, and oxidative stress.

Wait, better body weight? I thought they were given the same number of calories. Yes, both diets were isocaloric, the same calories. Yet just eating meat-free led to significantly more weight loss—about six pounds more; more waist loss, a slimmer waist; lower cholesterol, of course; and less superficial fat, meaning the external jiggly fat; and most importantly, significantly more visceral fat loss––the most metabolically dangerous deep belly fat. Same calories, yet more loss of body fat. And not surprisingly, better control of their diabetes. All in addition to leading more effectively to improvements in physical fitness.

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• Boutros GH, Landry-Duval MA, Garzon M, Karelis AD. Is a vegan diet detrimental to endurance and muscle strength? Eur J Clin Nutr. 2020;74(11):1550-5.
• Król W, Price S, Śliż D, et al. A Vegan Athlete's Heart-Is It Different? Morphology and Function in Echocardiography. Diagnostics (Basel). 2020;10(7):477.
• Veleba J, Matoulek M, Hill M, Pelikanova T, Kahleova H. "A Vegetarian vs. Conventional Hypocaloric Diet: The Effect on Physical Fitness in Response to Aerobic Exercise in Patients with Type 2 Diabetes." A Parallel Randomized Study. Nutrients. 2016;8(11):671.
• Kahleova H, Hrachovinova T, Hill M, Pelikanova T. Vegetarian diet in type 2 diabetes--improvement in quality of life, mood and eating behaviour. Diabet Med. 2013;30(1):127-9.
• Kahleova H, Matoulek M, Malinska H, et al. Vegetarian diet improves insulin resistance and oxidative stress markers more than conventional diet in subjects with Type 2 diabetes. Diabet Med. 2011;28(5):549-59.

Motion graphics by Avo Media

• abdominal fat
• athletes
• body weight
• caloric restriction
• calories
• cardiovascular health
• cholesterol
• diabetes
• exercise
• fat
• insulin
• oxidative stress
• Plant-Based Diets
• sugar
• vegans
• vegetarians
• weight loss