Breastfeeding does not protect babies against becoming overweight or obese children, according to a study of 10,000 mothers and babies.
Past research has suggested that babies who are breastfed are less likely to become obese.
But those studies compared mothers who chose to breastfeed, so they and their children could have been different in other important ways, researchers said.
Lead author Richard Martin, from the University of Bristol in south west England, said that while breastfeeding had other health benefits, it is "unlikely to have any effects on stemming the obesity epidemic".
The study, which appeared in Journal of the American Medical Association, included 17,000 mothers and babies in Belarus.
About half the babies were born at maternity hospitals that used a World Health Organisation-designed initiative to promote breastfeeding.
All mothers originally breastfed their babies, so the study was meant to compare how long infants were breastfed, rather than whether they were breastfed at all, Martin said. The program to encourage breastfeeding seemed to work. After three months, 43pc of mothers who gave birth at intervention hospitals were still breastfeeding, compared to 6pc in the comparison group.
Martin said over the years his team's study has found fewer stomach infections and eczema, as well as better memory skills among kids in the breast-feeding promotion group.
However, the researchers compared weight and body fat in 14,000 children who were tracked up to the age of 11 and found no differences tied to breastfeeding.
Between 14 and 16pc of all the children were overweight and about 5pc obese.