Frequent intentional weight loss may have significant long-term detrimental effects on the immune system, study results show. On the other hand, maintaining a healthy weight benefits immune function.
A research team from the Fred Hutchinson Cancer Research Center in Seattle, Washington studied 114 healthy, currently overweight sedentary postmenopausal women. The team found that the immune function of natural killer (NK) cells was significantly lower in those who had ever intentionally lost 10 pounds or more compared with those without this history.
Moreover, the cell-killing ability (or "cytotoxicity") of NK cells was increasingly lower with the number of times a woman reported shedding 10 pounds or more.
Two or more episodes were associated with substantially decreased NK cytotoxicity, with the lowest NK cytotoxicity seen in those reporting the highest frequency of weight loss. According to the team, frequent intentional weight loss reduced both the proportion and absolute number of NK cells.
Maintaining a stable weight over several years, on the other hand, was associated with significantly greater NK cell numbers and cytotoxicity.
Lower NK cytotoxicity could contribute to an increased incidence of viral infections, and thus, to lost productivity or decreased quality of life, the researchers said. They suggest using a sensible approach to weight loss that combines dietary changes with regular exercise. Exercise may be key, in that it helps to keep weight off and also may boost the immune system.
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