Frequent Weight Loss May Affect Immune Function.




J Am Diet Assoc

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Consumer Data: Obesity, Weight Loss
Professional Data: Obesity, Weight Loss


No one wants to be fat. Thin is in, especially today. The prevalence of slender, even skinny models in advertising is ample evidence of our society's attitudes about body weight. While being overweight is certainly unhealthy, the fear and loathing attached to body fat can also be detrimental when it leads to eating disorders such as anorexia. But consternation over the impact of obsession with thinness on our national psyche, especially where young people are concerned, should not obscure the obvious fact that too many Americans are overweight. Everywhere you look, people are fighting the "Battle of the Bulge." And it is certainly a positive trend that many of us seem more health-conscious these days.

Overeating and lack of exercise are the principle behavioral factors that lead to obesity. As technology and transportation dominate the 21st century, lifestyles have become increasingly sedentary. Societal pressure to produce and succeed leaves less time to plan and prepare wholesome meals. Add the ever-present ads for processed, high fat, high-sugar junk foods, and it is easy to see why obesity is so commonplace. At the same time, science is learning more about the physiology of obesity. Body fat, it has recently been discovered, contains a hormone called "leptin," that may be an internal anti-obesity factor.1 Leptin appears to play a role in appetite control; when nerve receptors for leptin are stimulated, appetite is suppressed. A relationship has been found between obesity and a deficiency of leptin or malfunction of leptin receptors. While the evidence is still preliminary, the leptin-obesity connection has been strengthened by positive results using synthetic leptin and leptin receptor-enhancing drugs on animals.

Investigators looked into the effects of “Yo-Yo” dieting on immune function. This study involved 114 healthy, inactive, overweight, postmenopausal women who were placed on an exercise regimen. Questionnaires were completed by these women to assess their past weight loss attempts. Then the Natural Killer Cell (NK) cytotoxicity was measured. These white blood cells are responsible for combating viruses, tumors, and are crucial to the immune system. After analyzing the data, the results showed that women who intentionally lost more than 10 pounds had lower NK cytotoxicity. In fact, the more times the women lost 10 pounds or more, the more their immune systems were suppressed. The authors concluded that, “this study provides evidence that frequent intentional weight loss may have long-term effects on immune function.”2


1. Halford JC, Blundell JE. Pharmacology of appetite suppression. Prog Drug Res. 2000;54:25-58.
2. Shade ED, et al. Frequent intentional weight loss is associated with lower natural killer cell cytotoxicity in postmenopausal women: Possible long-term immune effects. J Am Dietetic Assoc. Jun 2004;104(6)