Researchers made two significant findings regarding the correlation between immune function and weight loss. One of the findings showed that a woman’s immune function decreased in relation to the number of times she attempted to lose weight.

The other finding revealed that when a woman stayed at the same weight for many years, she was shown to have higher natural-killer-cell activity, a measurement of the immune system.

Components of The Study

• Participants included 114 overweight postmenopausal women who led sedentary lifestyles and were in good health.

• The women were questioned about their weight-loss history over the past 20 years.

• One of the requirements of the study was that the women were to remain at the same weight for three months before the study.

Results of The Study

• An isolated episode of losing 10 pounds or more over the past 20 years didn’t show any impact on the current natural-killer-cell activity.

• In the cases of several weight loss episodes over the past 20 years, there was a definite decrease in the number of natural-killer-cell activity. Women who reported over five attempts at weight loss had around a third less of the natural-killer-cell functions.

• Women who remained at the same weight for at least five years or more were shown to have 40 percent more natural-killer-cell function than those who maintained the same weight for two years or less.

Natural-killer-cells, also known as NK cells, are a critical component to the functioning of the immune system. Some of its valuable functions include destroying viruses and cancer cells. Decreased NK functioning has been linked to a rise in the cases of cancer and increased vulnerability to colds and other viruses.

Researchers noted that some of the limitations of the study were having to depend on self-recordings of weight-loss.

They recommended performing an ongoing longitudinal study, which would take place over a number of years, as a way to effectively assess the impact of yo-yo dieting on the immune system. They stressed this was particularly important considering 50 percent of Americans have tried to lose weight without positive long-term results.

Weight-loss Recommendations by The Experts

• Incorporate dietary modifications along with exercise

• Eat a lot of non-starchy vegetables and fruits and limit refined carbohydrate intake

• Stick to eating moderate amounts of lean protein, dairy products, legumes and whole grains

• Do some kind of cardiovascular exercise for at least 60 minutes a day, such as walking at a brisk pace

Experts concluded that exercise and proper eating habits were not only good weight loss strategies, but the two factors would also help improve the immune system in the long run.

Journal of the American Dietetic Association June 2004;104(6):903-12