Babies given formula milk instead of being breastfed are 25 per cent more likely to become obese.
Almost one in six bottle-fed babies are obese by the time they reach primary school, an international study of more than 100,000 six to nine-year-olds found.
Children never given breast milk have 25 per cent higher odds of obesity than those whose mothers exclusively breastfed them for at least six months.
Experts believe formula may cause babies to gain more weight and grow faster because it is developed from cows' milk, which has higher levels of protein and may trigger the growth of fat cells.