How can diet affect muscle size and strength?

    Written by:
    Mike Murray

    Fact-checked

    by:

    Natalka Roshak, Bill Willis
    Last Updated: May 16, 2025

    Diet significantly affects muscle size and strength by providing essential nutrients for exercise, recovery, and muscle building; a protein intake of 1.6 to 2.2 grams per kilogram of body weight and a carbohydrate intake of 3 to 5 grams per kilogram are recommended. Although carbohydrates are crucial for fueling resistance exercise, studies show that strength gains may not differ significantly between high-carbohydrate and low-carbohydrate diets due to the nature of strength-focused workouts.

    Nutrition plays an important role in increasing muscle size and strength by fueling exercise, promoting recovery, and providing the materials to build up muscle. These processes are mainly influenced by protein and carbohydrate intake. Evidence suggests that a total daily protein intake of 1.6–2.2 grams per kilogram of body weight is ideal for supporting increases in muscle size and strength.[1][1]

    Muscle glycogen is the primary fuel source during resistance exercise,[2] and glycogen depletion is associated with muscular fatigue and impaired muscle contraction efficiency,[3] so consuming at least 3–5 grams of carbohydrate per kilogram of body weight per day is recommended to maximize increases in muscle size and strength.[4][5]

    Nonetheless, many studies have not found differences in strength gains between higher- and lower-carbohydrate diets.[6] This is likely due to the fact that compared to muscle-gain-oriented workouts, those focused on strength adaptations tend to feature lower volumes and longer rest periods, relying less on carbohydrates for energy.