Childhood obesity, weight gain may be caused by high intake of antibiotics, study suggests

From 1980 to 2012, the rate of childhood obesity in children aged 6 to 11 years rose from 7 percent to about 18 percent, and 5 to about 21 percent in those aged 12 to 19 years, the CDC reports. In a new study published in the International Journal of Obesity, researchers showed a link between antibiotic exposure in children and an increase in body mass index (BMI), TIME reports.

Researchers conducted the largest and longest study so far determining how antibiotic exposure affects BMI, and found that the more doses and the longer kids consume antibiotics, the higher their risk for retaining weight gained and the higher their risk for gaining more weight over time.

According to Science World Report, researchers analyzed almost 164,000 children, aged 3 to 18, enrolled in Pennsylvania’s Geisinger Health System between 2001 and 2012. The scientists looked at body-mass index, antibiotic use, race, sex and other factors, and compared the typical BMI trajectory of children who did not take antibiotics against the BMI trajectory of those who took antibiotics. Results showed that those who took antibiotic gained a little weight, which they lost within the next year.

However, researchers also found that every time a child took an antibiotic, the weight gain became cumulative and progressive, widening the difference between their weight and the weight of the kids who did not take antibiotics. According to researchers, the consumption of antibiotics caused a weight gain of around 1.6 pounds to 3.3 pounds during childhood.

"This would suggest that this effect is not going to stop at age 18 [and] what’s happening is permanent," professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health and lead author Brian Schwartz said.

Wall Street Journal reports that according to scientists, antibiotics eliminate certain bacteria in the gut and leave behind others that break down food differently, resulting to an increase in the calories absorbed from food.

"A single antibiotic can wipe out an entire intestinal microbiome," Schwartz explained. "If antibiotics are infrequent, then the microbiome can recover. But if there are excessive antibiotics, then the impacts on the microbiome can last, and the ecology of the bacteria in the intestinal tract changes and doesn’t go back to what it was before."

While antibiotics are commonly prescribed by doctors, there is a growing concern due to antibiotic resistance. In fact, between 2000 and 2010, U.S. antibiotic prescription decreased by 18 percent for children.

Schwartz explained, "The more antibiotics you get, the stronger the effect, and this effect seems to get larger as you get older."