Infant feeding method and obesity: body mass index and dual-energy X-ray absorptiometry measurements at 9-10 y of age from the Avon Longitudinal Study of Parents and Children (ALSPAC)

Background: Previous studies reported inconsistent associations between breastfeeding and body mass index (BML in kg/[m.sup.2]). Associations with body fatness are unknown. Objective: We investigated the association of breastfeeding with fatness measured by dual-energy X-ray absorptiometry. Design: The prospective cohort study involved 4325 singletons with measurements at 9-10 y of age to assess the main outcomes of BMI and total and trunk fat masses. Results: Prevalence of any breastfeeding was 82%. In crude analyses. breastfeeding was inversely associated with total fat mass [% change per category increase (4 categories)] in breastfeeding duration (-4.4%; 95% CI: -3.1%, -5.6%) and trunk fat mass (-0.5%: 95% CI: - 1.1%, 0.1%); the odds of adiposity were measured by total [odds ratio (OR): 0.81 ; 95% CI: 0.75, 0.88] and trunk (OR: 0.78; 95% CI: 0.71,0.84) fat masses in the top decile. In adjusted models, the inverse association of breastfeeding with mean total fat mass was attenuated by 59% (% change per category increase in breastfeeding duration: -1.8%: 95% CI: -0.5%, -3.1%), but associations with trunk fat mass (% change per category increase in breastfeeding duration: -0.6%; 95% CI: 0.0%, -1.3%) and the ORs for total (0.76; 95% CI: 0.69, 0.84) and trunk (0.74; 95% CI: 0.67, 0.81) fat masses in the top decile were little altered. Children breastfed [greater than or equal to] 6 mo had the lowest odds of total fat mass in the top decile (OR: 0.45; 95% CI: 0.33, 0.62). In multivariate models, there was little evidence that breastfeeding was associated with mean or threshold values of BMI. Conclusions: The protective association of breastfeeding with mean total fat mass was attenuated somewhat after adjustment for con-founders, which indicated that confounding may explain this association. Breastfeeding may protect against obesity if maintained for [greater than or equal to] 6 too. KEY WORDS Avon Longitudinal Study of Parents and Children, ALSPAC, epidemiology, diet, prevention and control, energy metabolism, feeding behavior