Common drug used by millions linked to 20% higher obesity risk if taken before certain age

Exposure to the common drug before the age of two has been linked to a higher BMI in a new study

18:37, 25 Apr 2025

Exposure to a common medicine in early childhood has been linked to obesity in a new study(Image: Getty Images/iStockphoto)

A common infection-fighting could raise the likelihood of obesity in later life if taken as a toddler, according to new research.

The study, conducted by researchers in Finland, found that children who took antibiotics before the age of two were 20 per cent more likely to develop childhood obesity compared to children who were never prescribed the medicine.

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The researchers followed nearly 34,000 children born in Finland to see if antibiotic use at various points in pregnancy and early life was linked to higher BMI at age two and age 12.

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Not only did they find that children exposed to antibiotics in the first two years were more likely to have a body mass index (BMI) in the obese category, but they were also 10 per cent more likely to be overweight by the time they left primary school.

Children who took antibiotics before the age of two were more likely to develop childhood obesity(Image: PA)

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"Antibiotic exposure in the first two years of life has a stronger association with childhood weight gain than exposure during pregnancy stages or other early ages," said Sofia Ainonen, medical doctor at the University of Oulu in Finland and presenting author of the study.

"Providers need to be cautious about prescribing antibiotics for young toddlers, especially unnecessary antibiotics for upper respiratory tract infections," Ainonen added.

Nearly four million antibiotics prescriptions are given to children aged under 14 every year in the UK, official data shows. Amoxicillin is the most commonly prescribed antibiotic to children, accounting for 53 per cent of all antibiotic use in children aged 0-4 years old in the UK.

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Overuse of antibiotics is fuelling the growing threat of antimicrobial resistance(Image: PA)

Antibiotics are commonly used to treat suspected bacterial infections. However, according to the NHS, children do not often need antibiotics as most childhood infections are caused by viruses.

The UK Health Security Agency (UKHSA) warns that the overprescription of antibiotics is fuelling antibiotic resistance, which health officials warn is "the biggest threat to global health" and could make common infections harder to treat.

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The latest study suggests another health risk of taking antibiotics. Childhood obesity is an increasing health problem worldwide, with more than 159 million school-aged children diagnosed with obesity in 2022 alone.

Antibiotics are used by millions across the UK every year(Image: PA)

The authors wrote in the study: "Antibiotic exposure in the first 24 months of life was associated with a higher BMI at two years of age, compared to unexposed ones, and the same was seen in the long-term analysis until the age of 12 years."

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The research found no correlation between BMI and antibiotic use before pregnancy, during pregnancy, or at birth.

More studies are needed to fully understand the relationship between antibiotic exposure in early life and BMI – and to establish a causal link between the two.

The study will be presented at the Pediatric Academic Societies (PAS) 2025 Meeting, held between April 24-28 in Honolulu, Hawaii.