Eating excess calories triggers fat gain that’s not always revealed in pounds on the bathroom scale, according to a study.
In one of the most rigorous studies to date on differences among food types, researchers found that overeaters gain less weight if they shy away from protein. The results aren’t reassuring, said George Bray, an obesity specialist and the study’s lead researcher. Low-protein eaters gained just as much fat, and lost lean body mass, the study in the Journal of the American Medical Association found.
“There is nothing in medicine that would suggest losing lean body mass is a good idea,” said Bray, a professor at Louisiana State University’s Pennington Biomedical Research Center in Baton Rouge. “People on the low protein diet could think they were doing a good thing by gaining less weight, but they gained the same amount of fat and lost lean body mass.”
The results suggest the obesity epidemic may be worse than is currently known because those with lower body weight may have undetected layers of fat that can harm their health, the researchers said. About 65 percent of Americans are overweight, and one-third are considered obese, according to the U.S. Centers for Disease Control and Prevention.
The study tracked 25 young adult volunteers who agreed to live in a university metabolic unit for three months. Staff members prepared their meals, including an extra 1,000 calories a day, and watched to make sure they ate every bite. Volunteers were divided into three groups getting a low-protein, high-protein or normal protein diet, with the same calories.
Those getting just 5 percent of their calories from protein gained significantly less weight than those given more protein, adding 3 kilograms (6.6 pounds), compared with 6 kilograms (13 pounds), the study found. Volunteers in the highest protein group increased metabolism levels, though not enough to curb weight gain, and led to more lean body mass.
“The calories are the critical factor,” Bray said in a telephone interview. “Protein will change the scale weight, but not your fat rate,” he said. “Don’t be fooled by the scale, it may not be your friend.”
The study shows how low-protein foods with extra sugar and fat are contributing to the obesity epidemic, wrote Zhaoping Li and David Heber, from the University of California, Los Angeles’ Center for Human Nutrition, in an editorial.
“The Western diet tends to be high in fat and carbohydrates and low in protein,” they said. “Because this diet increases the risks of over-nutrition through fat deposition beyond that detected by body mass index, the method used to assess the current obesity epidemic and the magnitude of the obesity epidemic may have been underestimated.”