For some time, scientists have suspected that the increase in insulin level caused by carbohydrates in food can reduce longevity. A recent experiment with genetically altered mice (Irs2 knockout mice) demonstrated that less insulin receptor substrate-2 (Irs2) signaling throughout the body or just in the brain extended life span up to eighteen percent.
Usually, life extension has been achieved only by reducing the calories of the experimental animals. The interesting finding in this study was that it did not matter that the mice were overweight, hyperinsulinemic, and glucose intolerant. The mice with the disabled insulin receptor were more active and displayed greater glucose oxidation than the control mice. The scientists conclude that less insulin signaling in the brain can promote healthy metabolism, attenuate meal-induced oxidative stress, and extend the life span of overweight and insulin-resistant mice.
Some day, there may be a pill to make us live longer, but for now, the best bet is to eat moderately to prevent obesity and avoid the diseases associated with being overweight, such as diabetes, hypertension, and cardiovascular disease.
 Akiko Taguchi, Lynn M. Wartschow, Morris F. White, Brain IRS2 Signaling Coordinates Life Span and Nutrient Homeostasis, Science 20 July 2007: Vol. 317. no. 5836, pp. 369 – 372. DOI: 10.1126/science.1142179