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Antibiotics: repeated treatments before the age of two could be a factor in obesity

Antibiotics disrupt the intestinal flora (intestinal microbiota) and could be a factor in weight gain. Prescription of antibiotics for children should not be automatic but should be evaluated on a case-by-case basis.

Overweight and obesity are the result of an imbalance between energy intake and energy expenditure and can be associated with various known genetic, hormone, environmental and social factors.

There is some evidence that the intestinal flora can also be a factor, because of their role in energy metabolism. An infection, and likewise the number of antibiotic treatments, can alter the composition of the microbial flora and interact with the immune system. And this is thought to have long-term consequences on energy metabolism.

Although very diverse, 7 studies involving about 300 000 children converge to show that obesity is more frequent when children are exposed to antibiotics before the age of two, and that this is proportionate to the number of courses of treatment. Two other studies showed a relative increase of 10% to 50% in the risk of obesity in children exposed to four or more antibiotic treatments during their first two years of life, compared to children not exposed. Macrolides appear to be the antibiotics most often associated with higher risk compared with other antibiotics.

Although the level of evidence for all these data is low, there is convergence: obesity, excess weight and weight gain appear to be more frequent in children exposed to several systemic antibiotic treatments during their first two years.

The harm-benefit balance of antibiotic treatments for children should be considered on a case-by-case basis, and they should not be prescribed widely or automatically; macrolides should be reserved for cases of penicillin intolerance or treatment failure.

©Prescrire 1 June 2018

"Antibiotics during infancy: a risk factor for obesity?" Prescrire Int 2018; 27 (194): 155-157. (Pdf, subscribers only).

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