Breastfeeding has been found to generally reduce the risk of obesity. A number of studies have been published. Three good and moderate meta-analyses of methodological quality which infer that the risk of obesity is reduced in later life by breastfeeding have been published. Harder (2005) reviewed 17 studies including over 120,000 babies. They concluded that every month of breastfeeding was found to be associated with a 4% decrease in risk. Arenz (2004) reviewed 9 studies, 69,000 babies and concluded that breastfeeding appears to have a small (odds ratio 0.78, 95% CI (0.71, 0.85) but consistent protective effective against obesity. Owen (2005) reviewed 61 studies, 29,800 babies again found a reduced risk of obesity in later life even when confounding variables such as parental obesity, maternal smoking and social class were taken into account.

Harder T, Bergman R, Kallischnigg G et al (2005) Duration of breastfeeding and risk of overweight: a meta-analysis. American Journal of Epidemiology; 162:397-403

Arenz S, Ruckeri R, Koletzko B et al (2004) Breastfeeding and Childhood obesity: a systematic review. International Journal of Obesity related metabolic Disorders: 28: 1247-1256

Owen C, Martin R, Whincup P et al (2005) The effect of breastfeeding on mean body mass index throughout life: a quantitative review of published and unpublished observational evidence. Am. J. Clin. Nutr; 82: 1298-1307