NEW YORK  - When it comes to packing on body fat, the volume of calories you ingest seems to count more than whether those calories come from lots of protein, or very little.

Researchers found that people who ate high-calorie diets all gained about the same amount of fat. Those whose diets were low in protein gained less weight overall than people on high- and moderate-protein diets, but that’s because the low-protein group also lost muscle.

“Huge swings in protein intake do not result in huge swings in body fat gain,” said Dr. James Levine, who studies obesity at the Mayo Clinic in Rochester, Minnesota but wasn’t involved in the new study. “It really is the calories that count.”

Previous research has suggested that when people over-eat, the amount of weight they gain varies from person to person. Whether the make-up of individuals’ diets might be affecting how their body stores the extra calories has remained unclear. For the current study, researchers led by Dr. George Bray from the Pennington Biomedical Research Center in Baton Rouge, Louisiana, recruited 25 young, healthy volunteers to live in their lab and eat a prescribed diet for two to three months.