A new study suggests that giving babies antibiotics before they are six months old can increase the risk of them becoming overweight or obese.
American scientists, who carried out a study of more than 10,000 children in the Bristol area, believe that prescribing antibiotics to young babies can damage their developing digestive systems.
As a result, their chance of being overweight by the age of three increases by almost a quarter.
The Telegraph reports that new babies are sometimes given antibiotics to prevent serious infections being passed on from their mother during birth.
However, the National Institute for Health and Clinical Excellence warns that they are sometimes given out too readily. In the long term, this could also make antibiotics less effective as we develop a resistance to them.
Dr Leonardo Trasande, a paediatrician at the New York University school of medicine, said: "We typically consider obesity an epidemic grounded in unhealthy diet and exercise, yet increasingly studies suggest it's more complicated.
"Microbes in our intestines may play critical roles in how we absorb calories, and exposure to antibiotics, especially early in life, may kill off healthy bacteria that influence how we absorb nutrients into our bodies, and would otherwise keep us lean."
ABC Science reports that children who were treated with antibiotics in the first five months of their life weighed more for their height than those who were not.
Although the difference was small between 10 and 20 months, by 38 months of age, children who had taken the drugs had a 22 per cent greater chance of being overweight.
The effect was not as pronounced in older children as those who were treated with antibiotics from the ages of six to 14 months did not have a significantly higher body mass.