Early-life antibiotics linked to obesity?

Three studies have linked exposure to antibiotics in infancy with childhood obesity but these were all cohort studies which can only show an association, rather than proving cause or effect.1–3

The latest of these, published in November 2014,1 was a US study of nearly 65,000 children which reported a slight increase in the risk of obesity among children aged 2–5 who had been prescribed broad-spectrum antibiotics four or more times during their first 24 months. No increased risk was observed in children exposed to narrow-spectrum antibiotics such as penicillin and amoxicillin.