The weight gain that frequently accompanies aging may be influenced by your head - or at least your brain - according to new work published by Diabetes Center researcher Dr. Laurence Tecott.

Dr. Tecott, a UCSF Associate Professor of Psychiatry, has found evidence that “middle-aged” mice expend less energy and burn fewer calories to carry out the same physical activity that they used to do at a younger age. This increase in “energy efficiency”, or “miles per gallon”could be a factor in the weight gain that mice and many people experience as they grow older, and which plays a major factor in the development of type 2 diabetes.

Dr. Tecott has observed that in middle-aged mice, less energy is expended and fewer calories are burned than in younger-adult mice, even though each performed the same activity. This difference is especially pronounced in mice that are genetically engineered to lack a receptor for the neurotransmitter serotonin.

If the same is true in humans, Dr. Tecott says "this could mean that I'd burn less energy today running an 8-minute mile at a given weight than I would have 20 years ago."

Traditionally, scientists and health care professionals have thought that an increase in weight was due to declines in metabolic rate and physical activity levels, especially as we age. Dr. Tecott's research shows that other factors may also be at work to affect this "energy balance".

Serotonin is one of the chemicals in the brain that allows neurons to communicate with each other and controls many vital brain functions. The brain's serotonin receptors are already the target of numerous drugs such as appetite suppressants and anti-depressants. Dr. Tecott and colleagues now aim to determine whether targeting this receptor in a different way might offer aging patients "more bang for the buck of exercise" allowing a greater calorie burn to be achieved.

Dr. Tecott's research was recently published in the medical journal, Diabetes.