Researchers from Boston University School of Medicine (BUSM) have shown that intermittent access to foods rich in fat and sugar induces changes in the brain which are comparable to those observed in drug dependence. The findings, reported in the journal Proceedings of the National Academy of Sciences, may explain how abstinence from these foods contributes to relapse eating among dieters as well as related eating disorders.
Forms of obesity and eating disorders can be defined as chronic relapsing conditions with alternating periods of abstinence (dieting to avoid "forbidden" foods-rich in sugar and fat also known as palatable foods) and relapse (compulsive, often uncontrollable, eating of highly-palatable foods) that continue despite negative consequences. Although the positive reinforcing properties of palatable foods are well known, less attention has been given to the increased probability of a behavioral response produced by removal of an aversive stimulus (intake of palatable food to relieve negative emotional states).
The researchers used 155 rats to measure the neurobiological responses. The first group, the diet cycled subjects, repeatedly ate standard rat chow for five days, followed by a highly palatable, high-sugar, chocolate-flavored chow for two days. The second group ate only standard food. The amount of food consumed was not restricted for either group. When the diet-cycled rats were fed standard chow, they showed less motivation to obtain it, refused it, although it was previously acceptable, and they exhibited anxiety. However when the rats resumed eating the palatable food, they overate and their anxiety-related behaviors returned to normal.