Think because you’re thin you don’t have to exercise? Good DNA won’t get you out of gym class. Fitness is a greater predictor of longevity than body fat is, according to a study in the Journal of the American Medical Association.

So even if you’re blessed with skinny genes, you still have to huff and puff your way to cardiovascular strength. The research, which followed 2,603 adults over the age of 60, found that fit people outlived the out-of-shape, and that obese people who exercised regularly were less likely to die than sedentary people of normal weight. To get yourself in prime condition, lace up your walking shoes and hit the pavement for 30 minutes most days of the week.