Breast-feeding, adipokines, and childhood obesity.

One mechanism by which breast-feeding may protect against the development of childhood obesity is through the activity of components of breast milk. In an article published in this issue of Epidemiology, Weyermann et al found that overweight at age 2 years was associated with higher levels of adiponectin, a hormone secreted by fat cells, in the breast milk of mothers who breast-fed their infants for at least 6 months. This finding is surprising for several reasons: it is doubtful that infants absorb ingested adiponectin; prior literature suggests that adiponectin would reduce, rather than increase, risk for overweight; and the authors did not find associations with breast milk leptin, another adipokine. It is possible that adipokine exposure in infancy determines later weight status, but fundamental research is needed on associations of circulating adipokines with excess weight gain and on determinants of adipokine levels.