"In the study, 25 healthy participants were "divided into three groups getting a low-protein, high- protein or normal protein diet, with the same calories," and all were given "an extra 1,000 calories a day." Researchers found that participants "getting just five 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)," but "low-protein eaters gained just as much fat, and lost lean body mass," compared to high-protein eaters. Researchers concluded that "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."'

Note that carboyhdrates consumed were not adjusted.

I think it needs to be this simple. Tell people extra calories are extra calories. It doesn't matter if they came from a cookie or from eating a ton of carrots. This is also why Weight Watchers works because they teach people to count calories rather than omit this, eat this, drink that, etc.