BEIJING, Jan. 4 (Xinhuanet) -- A new research has found that low-protein foods with extra fat leads to unhealthy weight, according to Wednesday's Journal of the American Medical Association.

The resarch, in which 25 participants overate diets containing different levels of protein for a period, found that those who ate low-protein diets gained less weight than the other groups, but the quality of the weight gained was worse, as it came from an increase in body fat.

Everyone gained weight during the period. However, people in the low-protein diet lost 2.2 pounds (1 kilogram) in muscle mass, while those in the normal- or high-protein groups gained muscle mass. Muscle weighs more than fat, which is why they gained more weight. The excess calories turned to fat among participants who ate a low-protein diet.

In contrast, the high-protein diets led to changes in lean body mass and helped participants burn calories.

“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,” said George Bray, a professor at Louisiana State University’s Pennington Biomedical Research Center in Baton Rouge.

Researchers of the study encourage a high-protein, low-fat diet that is rich in colorful fruits and vegetables.