What is the best predictor for longevity? Many people may guess that weight is the key predictor. They assume that people who are thin will live longer than those who are overweight. Dr. Mark Stengler has reported on a University of South Carolina study in which researchers found that the best predictor of longevity is fitness level rather than weight. The best way to improve your fitness level is by regular aerobic activity. If you are having trouble getting motivated to exercise, see a clinical hypnotherapist for an exercise motivation session. Get fit, Be Well, live longer.