Frequent use of antibiotics appear to make children gain weight faster than those who have never taken the drugs, according to new research.

The study, published in the International Journal of Obesity, sggests childhood antibiotics may have a lasting effect on body weight well into adulthood, The New York Times reports.

For the study, researchers examined the medical records of 163,820 children ages 3 to 18, counting antibiotic prescriptions, body weight and height. The records, which covered pediatric exams from 2001 through 2012, showed that one in five — over 30,000 children — had been prescribed antibiotics seven or more times.

By the time those children reached age 15, those who took antibiotics weighed, on average, about 3 pounds more than children who had received no antibiotics.

“Not only did antibiotics contribute to weight gain at all ages, but the contribution of antibiotics to weight gain gets stronger as you get older,” said Brian S. Schwartz, M.D., the first author and a professor in the department of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health.