Most of us think that eating more food causes you to pack on the pounds, but it’s what we eat to gain that weight could determine exactly how much actual fat we’re packing on.

Researchers led by Dr. George Bray from the Pennington Biomedical Research Center in Baton Rouge, found study participants who ate 1,000 excess calories per day for eight weeks all gained weight, but accumulated body fat differently depending on the protein makeup of their diets.

Those who ate low-protein diets put on about seven pounds, compared to the 13 and 14 pounds gained by those in normal and high-protein groups, respectively. But while the low-protein group gained less weight, they stored more than 90 percent of their extra calories as fat and lost muscle mass, whereas the other participants gained both fat and healthier lean muscle.

What’s more, since our bodies use more calories to build muscle than to store fat, people on the higher protein diets burned more calories while their bodies were at rest.

Wondering how this applies to you? Most Americans tend to eat a high-fat, high-carb, low-protein diet — and this study shows that overeating on that type of diet will cause you to pack on fat, even you aren’t packing on pounds.

Dr. Bray summed up the results by saying, “The scale that you step on isn’t necessarily a good guide to the kind of weight you’re gaining … [It] can fool you into thinking that you’re winning when you aren’t.”