Prospective data from the CARDIA Study (4,995 men and women aged 18-30 years at baseline) was used to evaluate the association between changes in leisure-time walking and weight gain over a 15-year follow-up period. The mean weight gain was approximately 1 kg/year, and the mean duration of walking at baseline was less than 15 minutes per day. After taking into account several covariates, the greatest association between body weight and walking duration was for individuals with an elevated body weight at baseline (75th percentile). For instance, among individuals above the 75th percentile of body weight at baseline, 4 hours/week of walking was associated with 8 kg less weight gain in women and 4 kg less weight gain in men over the 15-year follow-up than their sedentary counterparts. These results emphasize the important role of physical activity in order to control the weight gain generally observed with age. This article was accompanied by an editorial underlining the fact that the study was the first long-term investigation conducted in a large sample of men and women to examine the impact of walking on body weight control. Results are of interest for public health reasons as walking is inexpensive, accessible, and accepted among adults. The study by Gordon-Larsen et al. is also the first to report an independent protective effect of walking on weight gain. It is hoped that these results will have an impact on public health guidelines.
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