Bogen DL, et al. The effect of breastfeeding with and without formula use on the risk of obesity at 4 years of age. Obes Res. 2004;12:1527-1535.
The purposes of this study were to determine (1) the shortest duration of breastfeeding required to have a protective effect against obesity, (2) whether formula lessened the effect, and (3) what, if any, maternal or child characteristics influenced the effect. The study found that exclusively breastfeeding for at least 16 weeks, or breastfeeding with some formula supplementation for at least 26 weeks, was associated with a reduced risk of obesity at age 4 in white children whose mothers had not smoked in pregnancy.