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SEATTLE, Jun 02, 2004 (United Press International via COMTEX) -- Yo-yo dieting, in which a person repeatedly loses and regains weight, may harm the body's immune function, U.S. researchers reported.
At the same time, maintaining the same weight over time appears to have a positive effect on the immune system, said researchers at the Fred Hutchinson Cancer Research Center.
The researchers interviewed 114 overweight but healthy post-menopausal women about their weight-loss history over the past 20 years. Based on the interviews, they found immune function decreased according to how many times a woman reported intentionally losing weight. Immune function was higher among women who had maintained weight over several years than those who had not.
Women who reported losing weight more than five times in the time period had one-third lower function of natural killer cells -- which attack viruses and cancer cells -- than women who maintained weight.
Researchers said these findings should not discourage healthy weight loss, which is recommended, but should alert dieters to avoid weight regain.
Copyright 2004 by United Press International.