The ketogenic diet is likely not the ideal diet for most athletes, but in some cases it could be useful. A ketogenic diet could help with weight loss for athletes in bodybuilding and for sports that have weight classes. The ketogenic diet has not been conclusively shown to increase the risk of losing lean body mass while in a caloric deficit, so it can be an option for weight loss, muscle growth, or maintenance diets.[1][2] Current evidence also suggests that ketogenic diets do not negatively affect aerobic fitness or endurance performance, although more research is needed in this area.[3][4][1]
Overall, the evidence remains inconsistent on the effect a ketogenic diet might have on endurance, sprint, and strength athletes.[5][6]