THERE’S A RUMOR going around the gym, and it goes something like this: Eat too much protein, and it’ll just get converted to fat.
Now, as dudes who eat roughly our body weight in chicken breast every week, we don’t like anyone talking smack about our best friends, so we decided to put this rumor to rest: Yes, eating too much protein can result in fat creation.
“Protein is insulinogenic, meaning it can stimulate an insulin response, which puts the body in storage mode,” explains Jackie Buell, Ph.D., C.S.S.D., an assistant professor and sports dietitian at Ohio State University. But here’s the thing: Your body has a harder time converting protein into a non-protein substance, and no study has yet conclusively shown how much protein you can eat before your body starts changing it to fat.
Chances are, though, that the protein-to-fat ceiling is pretty darn high, because tons of studies have researched what happens when people eat lots of protein, and none has reported changes in body fat composition.
A 2016 study in the Journal of Nutrition and Metabolism found that when healthy guys consumed 3.3g of protein per kilogram of body weight per day (g/kg/d) for four months, they didn’t gain any fat compared to when they ate a traditionally healthy diet. (Nor did they have any changes to their blood lipids or liver and kidney function, by the way).
Another widely cited study in the Journal of the International Society of Sports Nutrition found that when healthy, resistance-trained guys upped their protein to 4.4g/kg/d—that’s five and a half times the recommended daily allowance—their body fat didn’t go up whatsoever over two months. (Competing interest alert: One of the study authors is the CEO of the ISSN, which is sponsored by two supplement companies that supplied protein supplements for the study. Make of that what you will.)
What’s more, a small 2016 study published in the Journal of the International Society of Sports Nutrition found that when healthy guys ingested up to 3.3g/kg/d of protein and continued their normal strength regimen, they actually lost fat over the four-month period.
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