[Protective effect of breastfeeding against childhood obesity].

OBJECTIVE To review the literature concerning the hypothesis that breastfeeding has a protective effect against obesity. The biological plausibility of this hypothesis and the potential mechanisms involved are discussed. SOURCES OF DATA Articles published in indexed scientific journals, books and graduate theses and dissertations. Most articles were obtained from the Medline and Scielo databases using the keywords "breastfeeding," "overweight," "obesity," "children" and "adolescents" for the period between 1980 and 2002. Some articles were identified from the references cited in the first articles. SUMMARY OF THE FINDINGS Most studies report a protective effect of breastfeeding against childhood obesity. Some studies found no association between breastfeeding and obesity. One study including a small sample reported greater adiposity in breastfed children. Different definitions of exposure and outcome were used in different studies, making comparison difficult. Metabolic imprinting is suggested as a potential mechanism to explain the association. Behavioral aspects may also be involved. CONCLUSION Breastfeeding seems to have a protective effect against childhood obesity, but this issue still deserves further investigation.