Will Switching to a Vegan Diet Lower My Athletic Performance? Here's What Science Says

People are choosing to eat vegan more often lately. Currently, about 2.5-6 million people in the U.S. now eat a vegan diet. A randomized controlled trial in 2023 looked at how switching to a vegan diet affects strength and body composition in active people who lift weights. This randomized controlled trial was called “Change to a Plant-Based Diet Has No Effect on Strength Performance in Trained Persons in the First 8 Weeks-A 16-Week Controlled Pilot Study“ Nobody wants to lose those gym gains worked so hard on or all of a sudden have a lower performance.

So here is the question we want to know: “Will a vegan diet lower athletic performance?”

This is what the randomized controlled trial showed. A few small studies in runners and other athletes found no change or even some improvements in endurance with a vegan diet. One study saw no difference in strength gains over 12 weeks between vegans and meat-eaters when protein intake was the same.

However, athletes do need to pay more attention to a vegan diet to get enough total calories, protein, iron, zinc, calcium, and vitamin B12. If they work with a sports nutritionist and eat a balanced vegan diet, most athletes see no change in performance.

Now you may be wondering: “What happens if a meat-eater switches to the vegan diet?”

Well, here it is. In one 16-week study, they took 15 normal gym-goers who ate meat and had them record their normal diets for 8 weeks. Then they had them switch to a vegan diet for 8 weeks. They measured the participants' strength and body composition before and multiple times during the study.

This is what they found:

• No change in strength for bench press or leg press after switching to a vegan diet

• No change in body weight or BMI

• Those who went vegan ate about 60 fewer calories per day

• The vegan group slightly ate more carbs

• Protein intake decreased while on the vegan diet

So in these healthy, active adults, there was no gain or loss in strength in the first 8 weeks of going vegan. This was likely because calorie and carb intake stayed stable. However, during the vegan phase, protein intake went below athlete recommendations. Lower protein intake, may lead to reduced muscle growth when combined with strength training.

What are some other vegan diet health benefits of the vegan diet mentioned in this research article?

• Lower BMI and body fat

• Lower blood pressure

• Lower cholesterol

• Lower risk of heart disease and diabetes

• Less inflammation and better immune function

This is likely because the vegan diet is low in saturated fat, high in fruits, vegetables, beans and whole grains.

In conclusion, the vegan diet comes with several health perks. But athletes should work with an expert to ensure they get optimal macros, micros and calories to fuel performance.

Isenmann E, Eggers L, Havers T, Schalla J, Lesch A, Geisler S. Change to a Plant-Based Diet Has No Effect on Strength Performance in Trained Persons in the First 8 Weeks-A 16-Week Controlled Pilot Study. Int J Environ Res Public Health. 2023 Jan 19;20(3):1856. doi: 10.3390/ijerph20031856. PMID: 36767221; PMCID: PMC9914713.