Many studies suggest that some breastfeeding may be a protective factor against obesity. Our aim was to evaluate whether exclusive breastfeeding for six months, as recommended by the Danish National Board of Health, prevents obesity among children. A literature search found four epidemiological studies comparing children who were exclusively breastfed for six months with children who were never breastfed. Exclusive breastfeeding for six months reduced the risk of obesity among children 12 months of age. In children aged 3-14 years the result was inconsistent.