Ketogenic diets reduce performance in anaerobic exercise when compared to high-carbohydrate diets, according to a study published in The Journal of Sports Medicine and Physical Fitness. Researchers tracked performance for sixteen participants who consumed either a ketogenic diet or a high-carbohydrate diet for four days. Those who consumed the ketogenic diet lowered their average and peak performance power levels and ran shorter distances as well, compared with those who ate a high-carbohydrate diet. These data suggest low-carbohydrate diets impair intense, short-term physical activities. Source
