News & Research

Infant antibiotic exposures and early-life body mass. By Leonardo Trasande and colleagues. International Journal of Obesity, January 2013, pages 16–23

What is the problem and what is known about it so far?

Childhood obesity levels have skyrocketed over the past few decades, and scientists are eagerly seeking answers to the problem. Bacteria that live in the human gut are critical to health, and recent findings suggest they may help regulate body weight. Dysfunctional bacteria populations have been identified in the guts of obese people, suggesting that bacterial abnormalities may trigger weight gain—and the associated health problems—in their human hosts.

Why did the researchers do this particular study?

The womb is sterile, so a baby first encounters the bacteria that will reside in his or her body after birth. Early exposures to bacteria may be critical to establishing a healthy bacterial society in the gut. Antibiotics, taken early in life, may disrupt this process and lead to health problems later in life.

Who was studied?

The study included 11,532 children born in the United Kingdom between 1991 and 1992 who were a normal weight at birth.

How was the study done?

Researchers monitored the body weights of the children from birth to age 7, making note of any antibiotic use. They then looked to see if the age of the child at his/her first antibiotic exposure correlated with weight gain.

What did the researchers find?

Children who received antibiotics during their first six months gained more weight later than those who first received antibiotics after six months of life. The children who received antibiotics early were 22 percent more likely to become overweight by age 3 than those who did not receive them until later.

What were the limitations of the study?

Whether or not a child is overweight has been linked to several social and demographic factors, such as parental smoking. It is possible that one or more of these factors, and not antibiotic use, is the primary cause behind childhood weight gain. Even if antibiotics do cause weight gain, they still save lives, so it is unclear what the appropriate clinical application of such a link should be.

What are the implications of the study?

These findings suggest that early antibiotic exposure may increase the risk for weight gain later in life, but only before six months of age. More study is needed to determine what the long-term effects of this early weight gain may be.

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