Why are periods of dieting often followed by rapid weight gain or binge eating? Researchers at the University of Pennsylvania found that calorie restriction or dieting rewires the brain. In experiments with mice, researchers discovered that several genes regulating stress and eating changed after mice were calorie restricted to simulate human dieting. These gene changes persisted after mice were put on an unrestricted diet.
Mice on a continuous calorie-restricted diet are healthy and live longer than mice on a normal unrestricted diet. The researchers wanted to know what would happen if mice were put on cycles of a restricted diet, followed by cycles of non-restricted diet, similar to what many people do. Researchers fed the mice a restricted diet, which caused the mice to lose 10 to 15 percent of their body weight. This amount of weight loss is similar to what people achieve on a moderate diet. The “dieting” mice were more sensitive to stress, such as loud noises, than normal mice as measured by their stress hormone levels. When the mice were allowed to go back to their unrestricted diet and had gained back all their original weight, they were still more sensitive to stress. The ex-dieter mice had higher stress hormone levels and higher levels of appetite-stimulating hormones. Tracy Bale, the research team leader, says: “These results suggest that dieting not only increases stress, making successful dieting more difficult, but that it may actually ‘reprogram’ how the brain responds to future stress and emotional drives for food,’ as quoted by ScienceDaily.
New ways to think about dieting
The results from this study suggest that crash diets and even moderate diets will fail to keep the weight off once the diet is stopped, because the changes in genes and hormones will promote weight gain. So the best kinds of diets are continuous moderate diets or simply healthy eating habits.
Some people may find it difficult to follow an appropriate balanced diet and may need other treatment options. The ex-dieter mice were more sensitive to stress than normal mice. Stress has been linked to overeating. So far, all approaches to dieting deal with appetite suppression, calorie intake and the type of foods that should be eaten. These approaches have not worked for most dieters and even weight loss surgery does not always work. The researchers of this study suggest that treating stress during and after dieting may be more effective in reducing weight than other approaches. Discussing the changes in the genes and hormones in this study, the researchers write: “In humans, such changes would be expected to reduce treatment success by promoting behaviors resulting in weight regain, and suggest that management of stress during dieting may be beneficial in long-term maintenance” (Pankevich, D.E. et al.). Therefore, stress reduction is an untapped treatment approach to weight loss or keeping weight under control.
Pankevich, D.E. et al. Caloric Restriction Experience Reprograms Stress and Orexigenic Pathways and Promotes Binge Eating. J. Neuroscience (2010) 30: 16399