There’s a reason you see guys at the gym pounding a protein shake when their workout’s in the books: Adding more protein to your diet can enhance your muscle gains from weight training, a new review and meta-analysis from the British Journal of Sports Medicine concludes.
That’s what researchers determined after crunching the numbers from 49 previous studies involving 1,863 participants, where they lifted twice a week or more and took a protein supplement for at least a six-week duration. Protein types included whey protein, casein protein, soy protein, milk or milk protein, pea protein, whole food sources like beef or yogurt, or a blend of multiple protein sources.
Their conclusion? Dietary protein supplementation increased the gains you see when you strength train regularly—both in terms of upping your 1-rep max and putting on more lean muscle.
But it doesn’t seem to be a case where more is better: Supplementing with protein beyond 1.6 grams for every 2.2 pounds of bodyweight didn’t appear to have any added benefit, suggesting that was the max protein dose you need to get the greatest gains. That would mean, for example, that a 180-pound guy would take in just over 130 grams of protein a day.
It’s important to understand, though, that protein supplementation only enhanced the effects you see when you put in the work: For instance, strength training boosted 1-rep max increases by an average of about 60 pounds (when taking into account all the different measures the studies used to calculate them.) Adding protein supplementation to lifting boosted the increase by an average of just over five pounds—a change of about 9 percent.
When looking at muscle size, lifting alone—in a program of at least six weeks—increased lean muscle by about two and a half pounds. Protein supplementation boosted the lean muscle gains by 0.66 pounds.
That strongly suggests that the practice of weight training is far more potent in producing strength and muscle gains than simply adding protein is, the study authors say. So upping your protein when you’re slacking in the gym isn’t going to give you the gains you want.