When doing strength training, consuming more protein leads to greater muscle growth than consuming the same amount of calories from carbohydrates or fats.

We analyzed the available evidence on whether protein builds more muscle than carbs or fat during weight training, and what we’ve found so far is mixed. Fifty-three studies suggest that consuming more protein during strength training leads to greater muscle growth compared to getting the same number of calories from carbohydrates or fats, while forty-four studies do not show this same pattern [1]. This means that in some cases, higher protein intake appears to be linked with more muscle gain when combined with resistance exercise, but in other cases, it isn’t. The difference may depend on factors like how much protein someone already eats, their training experience, or how the studies measured muscle growth. We don’t have enough detail to say why the results vary, only that they do. Protein is made of amino acids, which are the building blocks muscles use to repair and adapt after training. Carbs and fats provide energy but don’t supply those same building blocks. Still, just because protein has a unique role doesn’t mean it always leads to more muscle — especially if total calories and training are the same. What we’ve found so far doesn’t confirm that protein is always better, but it also doesn’t rule it out. The evidence leans slightly toward protein having an advantage, but the number of studies refuting that idea is nearly as large. For someone lifting weights, this means focusing on getting enough protein each day — around 1.6 to 2.2 grams per kilogram of body weight — may help, but it’s not the only factor. Eating enough total calories and training consistently matter just as much.