YO-YO DIETING
Yo-yo dieting, also known as weight cycling, is a repeated loss and gain of body weight due to excessive dieting.
The term "yo-yo dieting" was coined by Kelly D. Brownell, Ph.D., at Yale University, in reference to the cyclical up-down motion of a yo-yo. In this process, the dieter is initially successful in the pursuit of weight loss but is unsuccessful in maintaining the loss long-term and begins to gain the weight back. The dieter then seeks to lose the regained weight, and the cycle begins again.
The reasons for yo-yo dieting are varied but often include embarking upon a diet that was initially too extreme. At first the dieter may experience elation at the thought of loss and pride of their rejection of food. Over time, however, the limits imposed by such extreme diets cause depression or fatigue that make the diet impossible to sustain. The dieter reverts to their old eating habits, and begins to rapidly regain the weight.
This kind of diet is associated with extreme food deprivation as a substitute for good diet and exercise techniques. As a result, the dieter may experience loss of both muscle and body fat during the initial weight-loss phase. After completing the diet, the dieter is likely to experience the body's famine response, leading to rapid weight gain of only fat. This is a dangerous fat-cycle that changes the body's fat to muscle ratio, one of the more important factors in health.
According to The US National Task Force on the Prevention and Treatment of Obesity, "yo-yo dieting" carries psychological and health hazards.
Repeated cycles of loss and gain take a psychological toll. Many dieters perceive each unsuccessful attempt to keep weight off as a personal failure. The result, over time, is the erosion of self-esteem together with depression and even guilt.
People who repeatedly lose and regain weight are weakening their immune systems. Women who have tried losing weight more than five times will have about a third lower natural-killer-cell function. In contrast, women who maintain the same weight for five or more years have 40 percent greater natural-killer-cell activity as compared to those whose weight had remained stable for fewer than two years.
Some studies suggest that weight cycling may also increase the risk for certain health problems such as high blood pressure, high cholesterol, and gallbladder disease.
http://en.wikipedia.org/wiki/Yo-yo_dieting
