(BATON ROUGE, La.) — It’s no secret that consuming excess calories leads to excess body fat, and new research suggests that, despite the belief that packing in a lot of protein can pack on the pounds, protein intake may actually have no impact on body fat.
But, says the study published in the Journal of the American Medical Association, protein consumption does appear to be associated with the gain or loss of muscle mass and how the body burns calories.
Researchers led by Dr. George Bray of the Pennington Biomedical Research Center in Baton Rouge, La., overfed 25 healthy adults during an eight-week period under very carefully controlled laboratory conditions. The participants were fed diets consisting of about 40 percent more calories than they normally consume. The only dietary elements that varied among participants were fat and protein levels: Some ate a low-protein diet (5 percent protein), others a normal-protein diet (15 percent), and a third group a high-protein diet (25 percent).
Participants who were fed the low-protein diet gained significantly less weight than the other groups, but all three groups gained a similar amount of body fat.
“The hypothesis was that the low-protein and high-protein diets might affect fat gain, but they didn’t. Fat gain isn’t modulated to any significant degree by protein intake,” he added.
Although participants in the low-protein group gained less weight, they also lost more muscle mass, which experts say could be detrimental to their overall health.
“Five percent [protein] is too low and is not good, even if one loses weight, as dietary protein is used to build and repair tissue. Low protein is a form of malnutrition,” said Carla Wolper, research faculty at the New York Obesity Research Center at St. Luke’s Hospital.
But that doesn’t mean people should gorge themselves on protein. The study’s normal and high protein groups gained muscle mass, but also gained body fat.
“What the public should take away here is that total caloric intake matters when it comes to weight gain,” said Lona Sandon, a spokesperson for the American Dietetic Association. “Choosing more of your calories from protein may help increase lean muscle mass, but people must keep calories in balance to avoid body fat gain.”
In an accompanying editorial, Drs. Zhaoping Li and David Heber of the Center for Human Nutrition at UCLA’s David Geffen School of Medicine wrote that the study highlights the importance of dietary protein.
“The results suggest that overeating low protein diets may increase fat deposition leading to loss of lean body mass despite lesser increases in body weight,” they wrote.
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