When it comes to packing on body fat, how many calories you eat seems to count more than where 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.

An experimental drug that chokes off the blood supply to fat cells helped obese monkeys slim down, a sign that it may work in people, too, U.S. researchers said on Wednesday.

The drug, known as Adipotide, takes a different approach from other weight loss medicines, which have generally tried to control appetite, alter the absorption of fat or increase metabolism in order to help people lose weight.