It’s well established that consuming protein after weightlifting helps repair and build muscle. But how much do you need in order to maximize muscle-protein synthesis? Experts have long believed that body weight dictates intake, but that anything above 25 grams of protein is moot. Not so fast.
A new study turns that whole more-brawn-more-protein thinking on its head. Exercise scientists from Stirling University in Scotland have determined that ideal post-exercise intake isn’t as much about body weight as the type and intensity of strength training. Also contrary to previous thinking, after certain resistance exercise sessions, 40 grams of protein is indeed more effective than 20 grams at stimulating muscle protein synthesis.
To determine this, the researchers recruited 30 resistance-trained men. They assigned those who weighed 143 pounds or less to the lower lean body mass group, and guys weighing 154 pounds or more to the higher lean body mass group. Both sets of men completed two sessions of whole-body resistance training in random order. After one, they were given 20 grams of whey protein; after the other, they got 40 grams. Next, the researchers took tissue samples to assess muscle-protein synthesis following each workout.
The biopsies revealed that in all men, regardless of how much lean muscle mass they had, muscle repair and growth was about 20 percent greater following ingestion of 40 grams of whey than after 20 grams. This shoots down the theory that you don’t glean additional benefits above 25 grams. Also, the results didn’t vary from one group to the other, meaning a 140-pound guy got the same benefit from 20 grams and from 40 grams of protein as a 160-pound man.
In other words, you shouldn’t just assume you need more protein than your buddy just because you’re bigger. “We think the reason we didn’t see a difference between the larger and smaller athletes is that the activation of the larger amount of muscle ‘swamps’ the response, so that having a more lean body mass doesn’t matter,” says Kevin Tipton, the lead researcher on this study.
Tipton notes that the results may have been different if they’d have pitted heavier, more muscular men against even scrawnier guys. Or if they’d had the men perform leg-only exercises, like most studies do, instead of total-body workouts. “Comparing our study to previous research,” Tipton says, “the simplest, most logical explanation is you’ll likely need more protein to get the maximum effect after a full-body workout than you would after doing only leg weights or only arm weights.”
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