Dose-dependent effects of training and detraining on weight in 6406 runners during 7.4 years.

OBJECTIVE: Prior randomized and non-randomized training studies have failed to establish a dose-response relationship between vigorous exercise and weight loss; this failure may be due, in part, to their short durations and small sample sizes. The objectives of this study were to determine whether exercise reduces body weight and to examine the dose-response relationships between changes in exercise and changes in total and regional adiposity.

RESEARCH METHODS AND PROCEDURES: This was a large prospective study of 3973 men and 1444 women who quit running (detraining), 270 men and 146 women who started running (training), and 420 men and 153 women who remained sedentary during 7.4 years of follow-up. The outcomes measured were weekly running distance, body weight, BMI, body circumferences, and bra cup size.

RESULTS: There were significant inverse relationships between the changes in the amount of vigorous exercise (km/wk run) and the changes in weight and BMI in men (slope +/- standard error: -0.039 +/- 0.005 kg/km per week and -0.012 +/- 0.002 kg/m(2) per km/wk, respectively) and in older women (-0.060 +/- 0.018 kg/km per week and -0.022 +/- 0.007 kg/m(2) per km/wk) who quit running, and in initially sedentary men (-0.098 +/- 0.017 kg/km per week and -0.032 +/- 0.005 kg/m(2) per km/wk) and women (-0.062 +/- 0.023 kg/km per week and -0.021 +/- 0.008 kg/m(2) per km/wk) who started running. Changes in waist circumference, an indicator of intra-abdominal fat, were also inversely related to changes in running distance in men who quit (-0.026 +/- 0.005 cm/km per week) or started running (-0.078 +/- 0.017 cm/km per week).

DISCUSSION: The initiation of vigorous exercise and its cessation decrease and increase, respectively, body weight and intra-abdominal fat, and these changes are proportional to the change in exercise dose.