Children who receive antibiotics often during childhood gain weight significantly faster than those who don’t, researchers found.
The findings suggest that antibiotics may have a compounding effect on body mass index, a measure often used to determine whether someone is at a healthy weight. Says study leader Brian S. Schwartz, a professor of environmental health sciences at the Johns Hopkins University Bloomberg School of Public Health:
“Your BMI may be forever altered by the antibiotics you take as a child. Our data suggest that, every time we give an antibiotic to kids, they gain weight faster over time.”
Antibiotics 7 or More Times
Schwartz and his colleagues analyzed electronic health records on 163,820 children between 3 and 18 years old who were patients of Pennsylvania’s Geisinger Health System. They examined body weight and height, which are used to determine BMI, and antibiotic use in the previous year as well as any earlier years for which Geisinger had records.
At age 15, children who had taken antibiotics seven or more times during childhood weighed about 3 pounds more than those who received no antibiotics, they found. Approximately 21 percent of the kids in the study, or almost 30,000 children, had received seven or more prescriptions during childhood.
Schwartz says that the weight gain among those frequently prescribed antibiotics is likely an underestimate. Children were not necessarily Geisinger patients throughout childhood, and the health system would not have records of antibiotics prescribed elsewhere.
“While the magnitude of the weight increase attributable to antibiotics may be modest by the end of childhood, our finding that the effects are cumulative raises the possibility that these effects continue and are compounded into adulthood,” Schwartz says.
Scientists working with penicillin learned early on that it caused weight gain in animals.
This led to the modern industrial farming practice of including small quantities of antibiotics in daily animal feed to fatten up the animals in an accelerated time frame. So a connection between antibiotics and weight gain does make biological sense, Schwartz says.
In humans, there has been growing evidence that antibiotics could lead to weight gain because of the effect that the drugs have on the microbiota, or the microorganisms that inhabit the body.
There are 10 times more bacterial cells in the human body than our own cells. Many do their work in the gastrointestinal tract, helping the body digest food and absorb nutrients.
Antibiotics kill off harmful bacteria but with collateral damage to bacteria vital to gastrointestinal health. Research has shown that repeated antibiotics use can forever change the microbiota, altering the way it breaks down food and increasing calories absorbed. This, in turn, can increase weight gain.
Prior studies had suggested that use in the youngest children may cause weight gain, but this study shows that use at any age during childhood contributes to weight gain that accelerates with age.
Schwartz says he thinks that physicians are becoming more judicious in their prescribing, but that can be difficult. Parents often demand antibiotics for apparent cold viruses and other ailments that the drugs cannot treat.
There have long been concerns that excessive antibiotic use is making bacterial strains resistant to potentially lifesaving drugs. But this study suggests that antibiotics also can have long-term negative effects in individual children, he says.
“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.”
B S Schwartz, et al.
Antibiotic use and childhood body mass index trajectory
International Journal of Obesity doi: 10.1038/ijo.2015.218