Yo-yo dieting or yo-yo effect, also known as weight cycling, is a term coined by Kelly Brownell at Yale University, in reference to the cyclical loss and gain of weight, resembling the up-down motion of a yo. In this process, the diet is successful in the pursuit of weight loss and is unsuccessful in maintaining the weight loss. 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 a hypocaloric diet that was initially too extreme. At first the dieter may experience elation at the thought of weight loss and pride in their rejection of food. Over time, however, the limits imposed by such extreme diets cause such depression or fatigue that make the diet impossible to sustain. Ultimately, the dieter reverts to their old eating habits, with the added effects of failing to lose weight by restrictive diet. Such an emotional state leads many people to eat more than they would have before dieting, causing them to rapidly regain weight. The process of regaining weight and especially body fat is further promoted by the high metabolic plasticity of skeletal muscle. The Summermatter Cycle explains how skeletal muscle persistently reduces energy expenditure during dieting. In addition, food restriction increases physical activity which further supports body weight loss initially. When food becomes available again, the thrifty program promotes the refilling of energy stores which preferentially occurs as fat catch-up.
This type of diet is associated with extreme food deprivation as a substitute for good diet and exercise techniques. As a result, the dieter may experience both muscle and body fat during the initial weight-loss phase (weight-bearing exercise is required to maintain muscle). After filling the diet, the dieter is likely to experience the body’s starvation response, leading to rapid weight gain of only fat. This is a cycle that changes the body’s fat-to-muscle ratio, one of the most important factors in health. A report by the American Psychological Association reviewed thirty-one diet studies and found that after two years of dieting up to a third of dieters weighed more than they did before they began the diet. One study in rats showed that they were more effective at gaining weight. However, the research compiled by Atkinson et al. (1994) shown that there are “no adverse effects of weight cycling on the body composition, resting metabolic rate, body fat distribution, or future successful weight loss”, and that there is not enough evidence for cardiovascular disease on cyclical dieting patterns. Yo-yo dieting can have extreme emotional and physical ramifications due to the stress that someone puts on themselves to lose weight quickly. The moment gratification of losing weight makes way to old eating clothes that causes weight gain and emotional distress. A more recent review concluded “… evidence for an adverse effect of weight loss, if it exists at all”. Since there is “no single definition of weight cycling [that] can be endorsed”,