❓Is it true that athletes and fitness enthusiasts can't eat vegetarian?

This claim has been thoroughly debunked by a huge number of real-world examples and studies — numerous professional tennis, marathon, NFL, and NBA athletes, along with weightlifters and powerlifters from multiple countries, have followed vegetarian or vegan diets long-term while reaching the top competitive level in their respective sports. From a nutrition science standpoint, athletic performance and muscle synthesis require adequate total calories, enough high-quality protein (roughly 1.6-2.0 grams per kilogram of body weight, with higher needs at higher training intensity), and proper training stimulus, and a plant-based diet can absolutely meet all of that. In multiple controlled studies, plant protein powders like soy and pea protein produce muscle-building effects very close to whey protein. Vegetarian athletes do need to plan their diet more carefully than omnivorous athletes (getting the same grams of protein requires eating a larger volume of food), but the claim that they "can't eat vegetarian" itself just isn't backed by evidence. A more accurate way to put it would be: vegetarian athletes need to plan their diet more diligently.