Relations of Sex Differences in Initial Body Mass Index and Physical Activity with Observed Changes over 12 Weeks among Children in the Youth Fit for Life After-School Care Intervention

Abstract

Relations of changes in Body Mass Index and voluntary physical activity, with sex, were assessed in children participating in the Youth Fit For Life after-school care program. Consistent with previous reviews and meta-analyses on children, the present physical activity effect sizes for improvements in Body Mass Index and voluntary moderate-to-vigorous physical activity were greater for girls (n = 75) than for boys (n = 60; overall M_age = 9.8 yr., SD = 0.8). The girls also had significantly higher Body Mass Index and fewer days of physical activity than the boys at baseline. When scores at baseline were controlled, correlations for sex with changes in the preceding measures over 12 wk. were not significant (r_12.3 = .06 and .15, respectively). Further study of the implications of children's sex in the health behavior-change process was suggested.