BALTIMORE, Oct. 22 (UPI) -- Children treated with antibiotics repeatedly in childhood gain weight faster than children treated less or not at all with the drugs, according to a new study.
The effect of antibiotics on weight has been known since at least the 1950s, one of two reasons the farming industry has included them in animal feed. Although living conditions and the realities of raising large numbers of animals together can lead to disease, which antibiotics can help control, farmers have been giving low doses of antibiotics to animals in order to increase yields of milk or muscle since early research with penicillin.
Antibiotics are known to alter the microbiome, the collection of microorganisms in the body that help with digestion and nutrient absorption.
"Your BMI may be forever altered by the antibiotics you take as a child," said Dr. Brian Schwartz, a professor at the Bloomberg School of Public Health at Johns Hopkins University, in a press release. "Our data suggest that every time we give an antibiotic to kids they gain weight faster over time."
Researchers analyzed electronic health data for 163,820 children between the ages of 3 and 18 collected by Geisinger Health System from 2001 to 2012. They considered height, weight, BMI and records of antibiotic treatment for the children, considering the possibility that some of them had been treated with anitbiotics outside of Geisinger.
The data showed 21 percent of the children, or 300,000, had been given antibiotics 7 or more times. By age 15, children who had been treated with antibiotics weighted on average 3 pounds more than children who had not.
The researchers suggest changes to the microbiome as a result of antibiotic use may be to blame for the weight gain. While antibiotics kill bad bacteria, they may also kill bacteria necessary for the body's ability to process food -- which can theoretically lead to weight gain, they said.
"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 said.
The study is published in the International Journal of Obesity.