January 4/ Los Angeles/KABC -- There are two schools of thought when it comes to weight loss diets: some say it is all about calories, while others say it is more about what you eat.

Experts are now providing some scientific guidance.

Daniel Kuhn is a big believer in portion control. However, for the sake of science, he allowed himself to over eat to see just how certain foods and different amounts of protein intake will affect his fats and muscle growth.

"I was eating a lot of real butter, for instance, real whipped cream and things of that nature that I don't normally indulge in," he said.

The idea was to examine how low, normal and high levels of protein affected the body when people were overfed by almost 1,000 calories a day.

"Fat storage was exactly the same with all three levels of protein," said Dr. George Bray, a diet researcher. "That is, it was the calories that they ate that affected the body fat that they stored."

Kuhn ate low protein and gained less than his protein-eating counterparts, but the low-protein group had less weight gain because they lost lean body tissue.

The normal and high protein group increased their lean body tissue. Losing lean body tissue is bad for health, Therefore, researchers say low protein diet was worse than the normal and high protein diet, even though it produced less weight gain.

"So protein has one set of effects, calories have another set of effects, and they are not directly connected," Bray said.

Researchers in the Journal of the American Medical Association say calorie intake remains the major determinant of whether people gain weight when they eat more than they should, although protein does influence what happens to lean body muscle mass. 

"I would encourage patients to watch their scales on a regular basis, so they can keep track of those added pounds and catch them early," Bray said.

For optimal health, experts say do not forget the body's basic building blocks: a healthy amount of carbohydrates, fats protein and water.

Researchers say participants eating low protein gained about half the weight of those on the normal and high protein diets.

 From the January 5, 2011, Prepared Foods' Daily News.