Babies born by caesarean section are at greater risk of becoming obese in later life than those delivered naturally.
The report said lack of exposure to beneficial bacteria in the birth canal could explain the link, reports the Daily Mail.
Given that obesity in pregnancy is a risk factor that leads to more caesarean section births, it may be that this relationship between the weight of mother and child explains the findings.
In the study, Brazilian researchers looked at obesity rates in 2,000 people aged 23 to 25.
They found 15 per cent of those delivered by caesarean were obese compared with 10 per cent of those born naturally.
Dr Helena Goldani, who carried out the study with colleagues at the Universidade Federal de Rio Grande do Sul in Porto Alegre, said that the findings did not prove a causal link between surgical deliveries and weight problems.
But she explained that, because infants born surgically are not exposed to beneficial bacteria in the birth canal, they might take longer to accumulate good bugs, which affect the metabolism.
Obese adults tend to have fewer of these friendly bacteria in their digestive tract than normal-weight people.
The study has been published in the American Journal of Clinical Nutrition.