There are people who say that ketohelps your athletic performance, and those who say it hurts it. "The literature is mixed on how an ultra low-carbohydrate diet like the keto diet affects athletic performance," says Grant Cox, C.S.C.S., head coach at Iron Tribe Fitness. But one thing is pretty clear: "A lot of it points to consistent decreases when athletes are looking for maximal power output (in weightlifting, vertical jumps,…

That might be part of the reason the keto diet is thought to be a better fit for endurance athletes. But even for them, evidence is mixed. "The ketogenic diet has been popular with athletes that engage in long endurance events, because it requires them to rely on less frequent carbohydrate feedings to fuel their exercise (think gummies, drinks, and goos) and more on their body fat stores," Brown explains. "This can decrease…