Obesity will be the greatest challenge for nutrition and is probably the greatest overall challenge to public health facing us in the next few decades. Being overweight or obese is a risk factor for many chronic diseases and the impact on wellbeing and mortality is well documented. Breastfeeding exclusively to six months of age is the most appropriate way to feed infants. A review of the international literature and an analysis of Australian data support the hypothesis that breastfeeding reduces the prevalence of obesity. Breastfeeding promotion should become a part of public health programmes for the prevention of obesity.