Good health and well being is partly achieved by a balance between caloric intake and expenditure. When caloric intake balance is disrupted by an excess of calories we gain weight.

The reason we consume more calories than needed is often thought to be psychological, but Maribel Rios, PhD, and Thaddeus Unger, graduate student at Sackler School, Tufts University School of Medicine, Boston, believe that appetites are regulated by 2 primary regions of the brain.

Researchers deleted a protein called brain-derived neurotrophic factor (BDNF) in animals and found they became significantly heavier than those animals with BDNF intact. Because the animals in the study were genetically altered to delete the BDNF gene in adulthood the researchers feel that it is a strong indication that BDNF acts as a satiety signal in the mature brain.

Because the animals did not show any signs of aggression, depression, or hyperactivity suggest that BDNF is not linked to behavioral control.

When the animals with the deleted BDNF gene were placed on a restricted diet, with the same level of calories as normal animals, they maintained a normal weight.