Antibiotic overuse is a problem that I discuss on a regular basis. One of the most detrimental effects of antibiotic overuse is the increase in obesity it is thought to contribute to. Dr. Smith recently blogged about the use of antibiotics during early infancy and its link to obesity later in life. A recent study published in the International Journal of Obesity adds to this research, finding that children who were exposed to antibiotics during the second or third trimester of pregnancy were at a higher risk of being obese at age seven. Infants born to mothers who delivered by Cesarean section were also at increased risk for obesity during childhood.

Of 727 mothers enrolled in the study, 436 were followed until the children reached age seven. Sixteen percent of the mothers used antibiotics during the second or third trimesters, which put them at an 84 percent increased risk for obesity compared with those children who were not exposed.

“Our findings should not discourage antibiotic use when they are medically needed, but it is important to recognize that antibiotics are currently overprescribed,” noted Noel Mueller, PhD. “Our findings provide new evidence in support of the hypothesis that Cesarean section independently contributes to the risk of childhood obesity.”

I wrote about the effects of antibiotics on the development of obesity in my latest book, The Skinny Gut Diet. Antibiotics alter the gut microbes in ways that lead to the development of obesity. Researchers are discovering that the type of bacteria you have in your gut determines whether or not you will be more likely to gain weight.

Setting up a healthy balance of gut bacteria early in life—and maintaining it throughout life—looks to be one of the best ways to avoid the weight gain trap that currently plagues two-thirds of the United States. Vaginal birth, breastfeeding, antibiotic use only when absolutely necessary, and a healthy diet rich in fruits and vegetables will go a long way toward establishing a healthy balance of gut bacteria. Probiotic supplementation can also help to support this balance.