Researchers from Boston University School of Medicine (BUSM) have shown that irregular access to foods rich in fat and sugar seems to stimulate changes in the brain which are comparable to those observed in drug addicts.
Forms of obesity and eating disorders can be defined as chronic relapsing conditions with alternating periods of abstinence and relapse that may continue in spite of negative consequences. Abstinence also known as dieting refers to avoiding ‘forbidden’ foods-rich in sugar and fat also called as palatable foods whereas relapse is a compulsive, often uncontrollable, eating of highly-palatable foods.
Though the positive reinforcing properties of palatable foods are recognized, less attention appears to have been given to the increased possibility of a behavioral response produced by removal of an aversive stimulus. Supposedly, aversive stimulus refers to intake of palatable food in order to relieve negative emotional states.
For the purpose of the study, the experts were believed to have used 155 rats to measure the neurobiological responses. They found that the first group i.e. the diet cycled subjects appear to have constantly ate standard rat chow for five days, followed by a highly palatable, high-sugar, chocolate-flavored chow for two days.
Whereas the second group seem to have eaten only standard food. Apparently, the amount of food consumed was not restricted for any group. When the diet-cycled rats were observed to have been fed standard chow, they showed less motivation to obtain it, refused it, although it was earlier acceptable, and they displayed anxiety. However when the rats resumed eating the palatable food, they seem to have over eaten and their anxiety-related behaviors returned to normal.
The study authors then examined the role of the brain’s stress system, which contributes to cycles of drug and alcohol binging and withdrawal, in driving these behaviors. They found that during abstinence from palatable foods, the rats were noted to have shown increased corticotropin-releasing factor (CRF) gene expression and peptide in the amygdala. Apparently, amygdala is an area of the brain involved in fear, anxiety and stress responses.
Moreover, similar to the anxiety, only when the diet-cycled group was fed palatable food did CRF levels appear to have returned to normal. Significantly, the blockade of the CRF receptor 1 with a selective antagonist may have been able to prevent all the behavioral outcomes of palatable food withdrawal. According to the experts, CRF is known to be a key stress neurotransmitter.
“In observing the activation of the amygdaloid CRF system during abstinence from palatable foods, we understood the causes of recurrent dieting failures,” says study co-author Pietro Cottone, PhD, an assistant professor and co-director of the Laboratory of Addictive Disorders in the Department of Pharmacology and Experimental Therapeutics at BUSM.
“CRF activation during abstinence from palatable foods induces a negative emotional state which is responsible for signs of anxiety and contributes to relapse to ‘forbidden foods. The stress experienced by frequent dieters in abstinence from palatable food has neurobiological similarities to the negative emotional state of drug and alcohol addicts,” adds study co-author Valentina Sabino, PhD, an assistant professor and co-Director of the Laboratory of Addictive Disorders in the Department of Pharmacology and Experimental Therapeutics at BUSM.
The findings of the study could perhaps elucidate how abstinence from these foods contributes to relapse eating among dieters as well as related eating disorders. This study is called as ‘CRF system recruitment mediates dark side of compulsive eating.’
The findings of the study have been published in the journal, Proceedings of the National Academy of Sciences.