Study: Antibiotics add weight to children

Oct 22, 2015, 4:24 PM EDT
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A study published in the International Journal of Obesity looked at records of 163,820 children ages 3 to 18. It found that one in five — over 30,000 children — had been prescribed antibiotics seven or more times. By the time those children reached age 15, they weighed, on average, about 3 pounds more than children who had received no antibiotics. The New York Times reports:

While earlier studies have suggested a link between antibiotics and childhood weight gain, they typically have relied on a mother’s memories of her child’s antibiotic use. The new research is significant because it’s based on documented use of antibiotics in a child’s medical record.
“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 Dr. Brian S. Schwartz, the first author and a professor in the department of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health.
Scientists have known for years that antibiotic use promotes weight gain in livestock, which is why large food producers include low doses of antibiotics in the diets of their animals.
Led by Brian Schwartz, professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health, the team looked at electronic health records of 142,824 children between the ages of three and 18 years. They broke down antibiotic prescriptions by what effect they had on BMI—whether it was temporary, or reversible and the weight that was gained associated with the drugs was lost within a year, or whether the effects were more long lasting, and the weight didn’t come off.
Reporting in the International Journal of Obesity, they found that having any antibiotic prescription in the past year (most received two prescriptions on average) before children’s BMI was measured resulted in a weight gain, but that this weight was lost soon after the medication was stopped. When the researchers looked at the cumulative effects of the drugs, however, they found that compared to children who did not take any antibiotics, those who did were more likely to gain and hold onto weight, and eventually even gain more weight by the time they were 18 years old.
“The more antibiotics you get, the stronger the effect,” says Schwartz. “And this effect seems to get larger as you get older.”
Overall, using antibiotics contributed to anywhere from 1.6 pounds to 3.3 pounds of weight gain during childhood.