Childhood antibiotics and weight gain: New study finds a lasting link

Treatments that fight off harmful bacteria could also affect bacteria that's vital to gastrointestinal health

The antibiotics you take during childhood could have a lasting impact on your weight, according to new research from the Johns Hopkins Bloomberg School of Public Health.

The findings, published Oct. 21 in the International Journal of Obesity, reveal that those who take antibiotics numerous times during childhood are more likely to gain weight quickly than those who don't.

"Your [body mass index] may be forever altered by the antibiotics you take as a child," says study leader Brian Schwartz, professor in the Department of Environmental Health Sciences at the Bloomberg School. "Our data suggest that every time we give an antibiotic to kids they gain weight faster over time."

The study found that kids who had taken antibiotics seven or more times during childhood weighed about three more pounds at age 15 than those who hadn't received antibiotics.

Researchers analyzed records from the Geisinger Health System in Pennsylvania, looking at 163,820 children between the ages of 3 and 18 from 2001 to 2012. They examined body mass index (BMI) using weight and height, as well as antibiotic use in previous years. Approximately 21 percent of the kids in the study, or nearly 30,000 children, had received seven or more prescriptions during childhood.

Schwartz notes that the weight gain this study uncovered is likely an underestimate, since the full antibiotic history wasn't known for many patients who didn't stay with Geisinger throughout their childhoods.

Though it's common knowledge that penicillin can lead to weight gain in animals, scientists in recent years have also found growing evidence that antibiotics can impact human weight. Research has shown that repeated use of antibiotics can forever change the microbiota, or the microorganisms that inhabit the body. While antibiotics kill off harmful bacteria, they also affect bacteria that's vital to gastrointestinal health, altering the way it breaks down food and increasing the calories of nutrients absorbed.

Past studies have found a link between antibiotic use and weight gain in very young children, but the new Johns Hopkins research suggests antibiotic use at any age of childhood contributes to weight gain that accelerates with age.

Schwartz says he thinks physicians have become more judicious in prescribing antibiotics, but that can be a challenge. Parents, for example, often demand antibiotics for treating their children even when the drugs may not be needed.

"Systematic antibiotics should be avoided except when strongly indicated," Schwartz says. "From everything we are learning, it is more important than ever for physicians to be the gatekeepers and keep their young patients from getting drugs that not only won't help them but may hurt them in the long run."

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Tagged obesity