Whether you eat too much or too little may depend on neurological circuitry in your brain, according to a new study from Harvard Medical School. Dr. Laura Holsen and her colleagues found that those who suffer from an eating disorder which can lead to starvation show less than normal activity in the hypothalamus, amygdala, and hippocampus areas of their brains. Conversely, those who suffer from an eating disorder characterized by an insatiable appetite show higher than normal activity in those areas. Dr. Holsen's team recruited people suffering from either anorexia nervosa or Prader-Willi Syndrome. Anorexics have a distorted image of their bodies and gradually starve themselves, sometimes to death, because they mistakenly feel that they are overweight. People with Prader-Willi Syndrome, on the other hand, cannot stop eating. Two other groups also participated: one was a group of people who are obese, and the other was comprised of people of normal weight. The research team hooked up participants to MRI technology to scan their brains, first after participants looked at pictures of food and then after they ate. The participants with anorexia or Prader-Willi syndromes showed the most differences in activity levels in the hypothalamus, amygdala, and hippocampus areas of their brains. Obese people and normal weight people had similar trends, but they were less extreme than the groups with eating disorders. Dr. Holsen, who is affiliated with Brigham and Women's Hospital in Boston as well as Harvard, said that her study may provide a new way to treat eating disorders through the development of new drugs that target certain regions of the brain active in the control of appetite and the sense of reward that food can elicit. The study was presented at the annual meeting of the Cognitive Neuroscience Society.