Could there be a link between obsessive-compulsive behavior and obesity? A brain circuit study designed to examine compulsive behavior inadvertently discovered a connection with obesity. Researchers from the University of Iowa bred mice missing a gene that they suspect is involved in compulsive behavior – compulsive grooming in this case. The mice offspring were not compulsive groomers, as you might expect, but the scientists were surprised to find that they also were not obese. The findings suggest that the brain circuits that control obsessive-compulsive behavior are intertwined with circuits that control body weight and food intake.
Lead researcher Dr. Andrew Pieper’s work is focused on compulsive behavior. His mouse model of compulsivity lacks a brain protein called SAPAP3. These animals excessively groom themselves to the point of causing lesions to the skin. Another researcher, Dr. Michael Lutter, is focused on mice lacking a brain protein known a MC4R. Mutations in the MC4R gene have been shown to be the most common single-gene cause of morbid obesity and over-eating in humans. Previous research suggested that MC4R might play a role in compulsive behavior, in addition to its role in food intake and obesity, which prompted Lutter and Pieper to test the possible interaction. Their experiment proved their hypothesis in terms of compulsive behavior, and also uncovered an unexpected outcome, deleting SAPAP3 restored normal weight in mice without MC4R -a lack of which would normally make them obese.
While obsessive-compulsive behavior and obesity may seem unrelated, Dr. Lutter believes that the link may be ingrained in the evolutionary need to eat safe food in times of a food abundance, and to decrease this drive in times of scarcity. He said “Obsessive behavior, or fear of contamination, may be an evolutionary protection against eating rotten food.” The study proposes that the circuit is involved in determining whether or not people should eat calorie-dense foods. Small disturbances in this circuit could lead to disorders that link anxiety and obsessive behavior to limited food selection or intake, including Tourette syndrome, anorexia, or obsessive-compulsive disorder. Alternatively, disturbances could lead to obesity, where people indulge in high-fat foods and may have less anxiety and obsessive behavior.
We asked Dr. Toby Broussard, expert weight loss surgeon in Oklahoma, for his thoughts on the new study. He said that the results are “interesting and could help explain part of the complicated mechanism that cause morbid obesity”. Next the researchers want to figure out how these two pathways communicate with one another, which they hope could lead to the development of new drugs to treat both compulsive disorders and eating disorders.
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Weight Loss Studies & Clinical