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Losing Weight May Lower Cholesterol, Boost Immunity

By Rosalie Marion Bliss
September 2, 2003

Scientists funded by the Agricultural Research Service found that volunteers with high cholesterol and/or triglycerides--who followed both a low-fat and low-calorie diet--not only lost weight, but also significantly enhanced their immune response. Experts estimate about 102 million Americans with high cholesterol are at increased risk of heart and other disease.

The lead researcher, Simin Nikbin Meydani, is director of the Nutritional Immunology Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, Mass. She and colleagues reported the findings in a recent issue of the Journal of the American College of Nutrition. ARS is the U.S. Department of Agriculture's chief scientific research agency.

The volunteers consumed different diets during four distinct test phases lasting more than one month each. The first three phases were designed to maintain body weight, and the last phase was not. The researchers tested the volunteers' immune functions through blood tests and skin-patch tests geared to measure immune response at the end of each phase.

As a baseline for comparison, the 10 volunteers were provided an average American diet with 35 percent of calories as fat (16 percent as protein and 49 percent as carbohydrate). The researchers then gave the volunteers three additional diets: one with 26 percent fat (reduced fat); one with 15 percent fat (low fat); and the last with 15 percent fat, but also with reduced caloric intake.

Cholesterol levels were significantly reduced during all phases, compared to the baseline-diet phase. But during skin-patch tests after the last phase, the volunteers showed significantly better immune responses than after any of the other three phases of the study. Blood tests also indicated enhanced cellular immune response.

The study's authors concluded that high-cholesterol individuals who follow recommended low-fat diets are unlikely to erode their immune systems, and they may well improve their immune response if they lose weight at the same time. The researchers now are planning more studies to gauge the effects of caloric restriction on health status and immune response in larger groups of volunteers.