When carbohydrates are consumed, the body releases insulin, which lowers the rate at which muscle proteins are broken down and slightly raises the rate at which new muscle proteins are made.

We analyzed the available evidence on whether carbohydrate intake reduces muscle breakdown and increases muscle synthesis through insulin, and what we’ve found so far is mixed. Fifty-one studies or assertions suggest that when carbohydrates are eaten, the resulting rise in insulin may lower the rate at which muscle proteins are broken down and slightly increase the rate at which new muscle proteins are made [1]. At the same time, 42 studies or assertions challenge this idea, indicating that the effect may be smaller, inconsistent, or not meaningful in real-world conditions. Insulin is a hormone the body releases after eating carbs, and it helps move glucose into cells for energy. Some research shows it may also act on muscle tissue to slow down the process of breaking down existing proteins and encourage the building of new ones. But other findings suggest this effect is weak, especially without protein intake, or doesn’t lead to noticeable changes in muscle growth over time. The evidence doesn’t clearly show whether this insulin-driven change is strong enough to make a practical difference in muscle retention or gain for most people. We don’t have enough detail to say whether the effect is the same across different people, activity levels, or diets. The number of supporting and refuting claims is close, and neither side clearly dominates. What we’ve found so far suggests insulin’s role in muscle metabolism is complex and likely depends on other factors like total protein intake, training status, and overall calorie balance. In everyday terms: eating carbs after a workout might help your muscles recover a little by lowering breakdown and nudging synthesis, but it’s unlikely to be the main driver of muscle growth. Getting enough protein and staying consistent with training probably matters more.