Ketogenic diet

A ketogenic diet severely restricts carbohydrate so that ketones become a more dominant fuel.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 126.} Roughly 50 to 100 g of carbohydrate a day is enough to prevent ketosis.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 126.} Keto is sometimes defined as 50 g or less, with fat often supplying 60% or more of calories to keep intake up.^{2Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 93.}

For fat loss, very-low-carbohydrate diets perform about as well as higher-carbohydrate diets and may improve satiety even when protein is matched.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 126.} Carbohydrate restriction isn’t necessary to lose fat.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 126.} Burning more fat for fuel doesn’t mean losing more body fat, because the client is also eating more fat.^{2Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 93.}

In practice

• Most people experience 1 to 4 weeks of fatigue, irritability and poorer performance while adapting.^{2Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 93.}
• Keto is a poor fit for muscle gain: competitive powerlifters and weightlifters lost 2.3 kg (5.1 lb) of lean mass in one crossover study.^{3Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 229.} Most keto groups in this research were probably also in a calorie deficit, which makes the cause hard to isolate.^{3Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 229.}
• Cutting out staples such as bread can make the diet harder to follow.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 126.}
• Helms and colleagues identify insulin resistance as the clearest use for low-carbohydrate diets and describe it as occurring mostly in sedentary people with obesity.^{4Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 94.}