Kids who repeatedly take antibiotics may gain weight faster than children who did not take them, according to a new study. The research, published online Oct. 21 in the International Journal of Obesity, suggests that frequent use of antibiotics in childhood may have a lasting effect on body mass index (BMI) well into adulthood.
“Your BMI may be forever altered by the antibiotics you take as a child,” study leader Brian S. Schwartz, MD, a professor in the department of environmental health sciences at Johns Hopkins Bloomberg School of Public Health, said in a news release. “Our data suggest that every time we give an antibiotic to kids they gain weight faster over time.”
For the study, Schwartz and his colleagues analyzed the electronic records of 163,820 children between the ages of 3 and 18. The researchers focused on body weight and height – the factors used to calculate BMI – and antibiotic use in the previous year, as well as any earlier years for which data existed.
The team found that approximately 21 percent of study participants, or about 30,000 children, had received seven or more prescriptions for antibiotics during childhood. Among this group, findings showed that by age 15, the children weighed three pounds more than those who had received no antibiotics.
Schwartz said that the weight gain among those who had frequent antibiotic use is likely underestimated because the researchers did not have the health records for participants throughout their entire childhood. He also noted that the effect of certain antibiotic types was even stronger than the overall average.
Then there is the long-term impact. “Our models suggest that the effect is likely to continue into adulthood and the BMI trajectories of children who did and did not receive antibiotics are increasingly divergent at older ages,” Schwartz told CBS News. “Although we did not observe children past 18 years, I would bet that this kind of pattern would continue.”
Scientists have long known that antibiotics cause weight gains in animals. In humans, there is growing evidence that antibiotics could lead to weight gain because of the effect they have on the microbiota – the microorganisms that inhabit the body.
Antibiotics kill harmful bacteria but also do in those vital to gastrointestinal health. Research has shown that that repeated use of antibiotics can forever change gut microbiota, altering the way it breaks down food and increasing the calories of the nutrients it absorbs. This, in turn, can lead to an increased weight gain.
Schwartz emphasized that the study findings do not mean that children should never take antibiotics. They can be life-saving and, in some instances, life-long prophylaxis antibiotics are necessary.
Still, Schwartz cautioned against the misuse of antibiotics for treating cold viruses and other ailments that will not be eased by the drugs. He called on 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.”
And to parents, Schwartz offered this advice in a CBS News interview: “If your doctor tells you that you or your child does not need antibiotics, don’t ask for them, don’t take them, don’t try to find another doctor who will give them to you. Don’t change your gut microbiota unnecessarily by taking antibiotics if you don’t need them.”