The effects of changing exercise levels on weight and age-related weight gain

To determine prospectively whether physical activity can prevent age-related weight gain and whether changing levels of activity affect body weight. The study consisted of 8,080 male and 4,871 female runners who completed two questionnaires an average (+/-standard deviation (s.d.)) of 3.20+/-2.30 and 2.59+/-2.17 years apart, respectively, as part of the National Runners' Health Study. Changes in running distance were inversely related to changes in men's and women's body mass indices (BMIs) (slope+/-standard error (s.e.): -0.015+/-0.001 and -0.009+/-0.001 kg/m(2) per Deltakm/week, respectively), waist circumferences (-0.030+/-0.002 and -0.022+/-0.005 cm per Deltakm/week, respectively) and percent changes in body weight (-0.062+/-0.003 and -0.041+/-0.003% per Deltakm/week, respectively, all P