PHILADELPHIA (CBS) – We talked about this many times before. What is the best diet to not just lose weight but to keep it off?

Harvard University researchers have been at this for quite some time. They believe there are certain common criteria that all diets should follow.

First, there needs to be emphasis placed on portion size. Meals should not be too big. The second most important point is the nutritional content of meals and finally, in fact, most importantly, the fat content of meals.

Researchers say the South Beach diet, a popular trendy diet, is very effective because it encourages the body to burn fat before the fat can be converted into tissue. Using fat as an energy source is the best way to rid the body of it but the key premise of the South Beach diet is to reduce the sugar, preprocessed foods, and carbohydrates.

But according to the Harvard scientists, the most important factor is that sticking to a higher protein and lower fat diet can help in losing weight and maintaining weight loss.

Reported By Dr. Brian McDonough, KYW Newsradio Medical Editor

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