A new study in this week's New England Journal of Medicine evaluates the health effects of three of the most popular diets to combat overweight and obesity.  VOA's Jessica Berman reports from Washington obesity has reached epidemic proportions globally and is a risk factor for illness and death.

According to the World Health Organization, 1.6 billion adults are overweight or obese, putting them at risk for heart disease, diabetes and cancer.  That number is expected to soar to 2.3 billion by 2015, owing to fast food and under-active lifestyles.

Experts agree that getting the weight off can be life saving, but an international team of researchers wanted to find out the long-term health effects of three of the most popular diet plans.

Investigators compared the standard calorie-reduction diet, the Mediterranean diet that is high in olive oil and grains, and the popular high-protein diet in a group of 322 middle-aged, moderately obese individuals working at a research center in Israel.

At the end of the two year study, researchers found those on the high-protein diet lost the most weight at 4.7 kilograms and kept it off, followed by those on the Mediterranean diet at 4.4 kilograms.  Those on the calorie-reduction diet lost the least amount of weight - 2.9 kilos.

More important, according to study lead author Iris Shai of Ben Gurion University of the Negev, were the cholesterol levels.

Shai says the high protein dieters, who were not calorie restricted, had a 20-percent reduction in their total cholesterol levels compared to a 12-percent reduction among low calorie dieters, whose plans included carbohydrates.

Shai says that could be important for a dieter with high cholesterol who has to lose weight. "So maybe the message here is carbohydrates must be much more risky than we thought and omitting them benefit obese patients."

Among diabetic participants, researchers found the Mediterranean diet did a better job in maintaining blood glucose levels.

Lawrence Cheskin runs a diet and nutrition program at Johns Hopkins University in Baltimore, Maryland.  For now, Cheskin cautions against reading too much into the study. "You know, even though we have studies such as this one that we are discussing suggesting that you can lose weight better on a low carbohydrate diet, we have the evidence from many people in non-Western countries that a low fat, relatively high carbohydrate diet results in good weight control," he said.

Meanwhile, Shai believes the results of her study in the New England Journal suggest that people need to work with their doctors to tailor a weight loss reduction plan to their particular medical needs.