For many people, stress and weight gain go hand in hand. Researchers, however, have maintained that stress-related fatness is triggered indirectly by unhealthy habits like overeating, smoking or excessive alcohol consumption, originating from emotional discomfort. Georgetown University scientists have now discovered a direct biological connection between stress and obesity in mice in a study published in Nature Medicine (2007; 13, 803–11).

Scientists found that when mice experienced repeated bouts of stress and were provided with a high-fat, high-sugar diet, they gained abdominal fat. Stressors directly trigger the release of a neuropeptide Y (NPY) in the body, stimulating the growth of fat cells in the belly area. (NPY triggers the growth of immature fat cells, causes mature fat cells to grow larger and promotes the formation of blood vessels necessary to sustain fat tissue.) The localized abdominal fat gained by the mice in this study contained high concentrations of NPY, and the mice soon developed the equivalent of metabolic syndrome in humans.

The researchers cautioned that mechanisms for weight gain might not be the same in humans as they are in mice. The authors hypothesized that drugs that prevented the release of NPY could inhibit the growth of abdominal fat cells. More research is required.