What makes for a long and healthy life? Why, you say, how about a healthy diet and liberal quantities of exercise? True! A healthy lifestyle keeps you in shape and is one factor that promotes longevity. But have you ever wondered exactly how this works on a physiological level? How does the brain understand you skipped the gym all summer and had French fries for lunch yesterday?

The answer, according to the results of a new study published in Science (July 2007), could relate to insulin levels in the brain. Researchers induced lab mice to overeat until they became obese and some exhibited symptoms of diabetes. Yet some of those same mice actually lived eighteen percent longer than their slender mice buddies. The researchers attributed that longevity to a gene that affects insulin. Put simply: the longevity gene (called Irs2) effectively "tricked" the brains of those mice into thinking they were slim and fit, when in fact the opposite was true.

For diabetics, the study raises an additional question: if raising insulin levels decreases the body's sensitivity to it, is it really desirable to treat type 2 diabetics with insulin over the long-term? Lead author of the study, Morris White of Children's Hospital in Boston, says it's highly preferable (when possible) to get type 2 diabetes under control through old-fashioned diet and exercise, rather than through insulin or other meds.