Well duh!

"They were given those extra calories as either a low-protein diet (5% of calories from protein, about 1.6 ounces of protein a day); normal-protein diet (15% of calories from protein, 5 ounces a day) or a high-protein diet (26% of calories, 8 ounces a day).

The carbohydrates stayed the same at 41% of calories."

You will be more likely to over eat from hunger if you eat a low fat low protein diet.