A small part of the brain, not the sin of gluttony, may be responsible for that urge to heap on another scoop of ice cream, according to research from the School of Medicine.

An international team led by Dr. Tamas Horvath, neurobiology professor and chair of comparative medicine, and researchers in Germany identified two adjacent regions in the brain mandatory for hunger regulation. The study, published this month in Nature Neuroscience, found that one region suppresses appetite while the other promotes it.

The discovery was made by destroying cells in the promoter-region of mice. These animals demonstrated reduced hunger and were eventually diagnosed with acute anorexia, while weight gain and obesity were observed in mice whose appetite suppressing neurons were attacked.

It is generally thought that a complex system of hormones, neurons and proteins are responsible for the regulation of hunger. The results of this study suggest these specific neuronal regions play an extremely important role in the entire process, Horvath said.

“This kind of scheme, of promoter and suppressor, has been around before,” Horvath said.

Dr. Pasko Rakic, chairman of the Department of Neurobiology, said the real significance of the study was not the results, but the experimental procedure employed. The ability to target and destroy specific neuron cells allowed the researchers to provide final proof for a well-accepted theory of appetite control, and this method could be used in various other applications.

The study, begun two years ago, has implications for pharmaceutical endeavors. Using knowledge of these two regions, scientists can design drugs to alter appetite and combat eating disorders. Horvath said the pharmaceutical industry was pursuing research in this area before his paper was even published. None so far have achieved any success, he said, even though scientific understanding of hunger and appetite control has been progressing.

“[This] research will clarify the avenues they’ve already been taking,” Horvath said.

The current treatment for weight-related disorders involves primarily addressing psychological issues, Yale Center for Eating and Weight Disorders co-director Marlene Schwartz said. The common treatment for eating disorders is designed to help the person change their behavior and the way they think about food through self-monitoring, challenging distorted thoughts, and finding new ways to cope with negative emotions, she said.

“One of the most challenging aspects of treating both eating disorders and obesity is knowing that neither are simply due to psychological issues,” Schwartz said in an e-mail. “We know that there are many genetic and biological factors that influence our patients.”

Everyone has an innate set point that defines their balance of satiety and hunger, Horvath said, and the nature of this point often explains why some people are obese and others are not. However, a drastic change in diet can move this point closer to an extreme.

“Exposure to extreme diets could even change your set point,” he said.

Horvath said he and his collaborators plan to continue researching appetite control. He said the next step is to look more closely at the relationship between the suppressing and promoting regions of the brain. This research provides a starting point for greater understanding of how the feeding center develops and interacts with other parts of the brain, Rakic said.