Children under the age of 24 months who use broad-spectrum antibiotics have a higher risk of obesity in early childhood.

Childhood obesity has become a major epidemic in the U.S. In fact, the condition has more than doubled in children and quadrupled in adolescents over the past three decades. Overweight and obesity result from “caloric imbalance” — to enough calories burned compared to the amount of calories consumed — and are affected by genetic, behavioral, and environmental factors.

L. Charles Bailey, M.D., Ph.D., of the Children’s Hospital of Philadelphia, and colleagues analyzed primary health care facility electronic health records from 2001 to 2003. In total, 64,580 children were enrolled, and were followed until five years of age.

The researchers discovered that 69 percent of the children were administered antibiotics before the age of two years, with an average of 2.3 bouts of antibiotics per child. The researchers also found that those who used broad-spectrum antibiotics more frequently had a greater risk of childhood obesity. There was no association found between childhood obesity and narrow-spectrum antibiotics.

The prevalence of obesity was 10 percent at two years of age, 14 percent at three years, and 15 percent at four years in all children.

“Because obesity is a multifactorial condition, reducing prevalence depends on identifying and managing multiple risk factors whose individual effects may be small but modifiable. Our results suggest that the use of broad-spectrum outpatient antibiotics before age 24 months may be one such factor,” said Bailey in a statement.