The researchers then looked at 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 showed increased corticotropin-releasing factor (CRF) gene expression and peptide in the amygdala, an area of the brain involved in fear, anxiety and stress responses. Similar to the anxiety, only when the diet-cycled group was fed palatable food did CRF levels return to normal. Importantly, the blockade of the CRF receptor 1 with a selective antagonist was able to prevent all the behavioral outcomes of palatable food withdrawal.

According to the researchers, CRF is 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," said 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,'" added 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 stress experienced by frequent dieters in abstinence from palatable food has neurobiological similarities to the negative emotional state of drug and alcohol addicts."

Source: Boston University Medical Center