Yoyo dieting is the situation in which a person's weight fluctuates up and down repeatedly over a period of weeks, months or even years. It is generally not a consciously determined condition, but is rather the result of multiple periods of dieting and weight loss interspersed with other periods of weight gain, lack of exercise and potential overeating.
Yoyo dieting has long been the cause of frustration among women who hope to maintain a single weight for an extended period of time. However, yoyo dieting of this type and frequent weight fluctuations can also negatively impact your immune system. The reason for this is that people who have experienced changes in weight have a more difficult time constructing natural killer cells, which are an important part of the immune system.
Yoyo Dieting and Immune System Effects
When your weight moves up or down, your body takes a certain period of adjustment time in order to recalibrate certain systems. Among these are your immune system and your metabolism. For the immune system, you may be temporarily weakened and prone to sickness, particularly if the weight gain or loss happened over a short period of time (as is the case with crash diets and extended periods of binge eating). Generally speaking, you'll be more likely to get sick and have a lowered immune system if you've recently gained or lost weight overall.
Yoyo dieting may have more serious and long term effects on your immune system as well. Studies have shown that women with prolonged or multiple periods of weight gain and loss were less likely to produce sufficient natural killer cells, or NK cells. NK cells are responsible for attacking viruses and other pathogens that may ultimately lead to illness once they enter your body. With fewer of these active NK cells available to help protect you and to stop diseases from affecting your system, you'll be more prone to disease and infection.
Other Dangers of Yoyo Dieting
The other risks of yoyo dieting over the long term have more to do with your metabolism. Frequent metabolism shifts put extra strain on your body. This may lead to a difficulty in controlling your metabolism and a general slowing of the metabolism. The latter of these typically makes it much harder to lose weight in the end. Yoyo dieting may also put other strains on different parts of your body, as your system must constantly recalibrate to deal with a new weight.
Some minor change in weight is consistently minor in the effects on your body. However, if you lose more than a few percentage points of your body weight, or if you gain that much weight, you may run into problems associated with yoyo dieting. The best way to ensure that your immune system is healthy is to maintain a stable weight through healthy, balanced diets and moderate (but consistent) exercise.