Background: Hypothesis 1--sustained changes in physical activity are inversely related to changes in body weight. Hypothesis 2-those who attenuate weight gain because of a temporary increase in physical activity (PA) may maintain a lower body weight over time.
Methods: Data were from the Coronary Artery Risk Development in Young Adults (CARDIA) Study, a cohort of black and white men and women, aged 18-30y at baseline, who attended up to five examinations over a 10y period (n=5,115 at baseline). Longitudinal associations between physical activity and body weight changes were assessed, adjusting for secular trend, age, clinic site, education, smoking, alcohol intake, parity, percentage energy intake from fat, and changes in these variables over time. For hypothesis 1, concurrent associations of physical activity and body weight changes were examined. For hypothesis 2, we explored whether weight gain attenuation associated with increased PA during the initial 2-3 y of follow-up was sustained over 5 y. The study 2 analyses were conducted with three separate 5y intervals: baseline to year 5 (n= 3,641), years 2-7 (n= 3,160), and years 5-10 (n= 2,617).
Results: Hypothesis 1 -change in physical activity was inversely associated with change in body weight within all four race and sex sub-groups (P<0.005). The predicted weight change associated with change in physical activity was four to five times larger in participants who were overweight compared with those who were not were overweight at baseline. Hypothesis 2-an increase in physical activity during 2-3 y of follow-up was associated with an attenuation of weight gain that was sustained through 5y of follow-up whether or not the physical activity increase was maintained during the later years. This finding persisted whether the starting point for the 5y follow-up was year 2, year 5 or baseline (women only). Comparing participants who increased physical activity with those who decreased physical activity in the first 2-3 y of follow-up (eg by at least 2 h per week of stationary cycling for at least 6 months per year), the mean 5y weight gain attenuation ranged from 0.8 to 2.8 kg.
Conclusions: The results of these analyses support the need for public health messages for promoting increased physical activity for weight maintenance and attenuation of age-related weight gain, especially for higher weight sub-populations.