Antibiotics have been used to promote weight gain in the agricultural industry for decades. This effect is believed to be mediated via the gut microbiome, and the effects of antibiotics on animal weight are greater when the drugs are given earlier in life.
However, little is known about the effects of antibiotics on human weight gain, despite evidence of their overuse in pediatric populations.
Frank I. Scott et al examined the association between antibiotic administration to children younger than 2 years and development of obesity by 4 years of age. They collected data from 21,714 children, from 1995 through 2013 in the United Kingdom.
They performed logistic regression analyses, adjusting for maternal and sibling obesity, maternal diabetes, mode of delivery, socioeconomic status, year and country of birth, and urban dwelling.
Of the children studied, 1306 (6.4%) were obese by the time they were 4 years old.
Increasing poverty, urban dwelling, year of birth, maternal and sibling obesity, maternal diabetes, and obesity in the first year of life were associated with an increased risk of obesity at age 4 years.
Antibiotic exposure was associated with a 21% increase in risk of obesity at age 4. Furthermore, risk of obesity increased with increasing number of courses of antibiotics and with antibiotic use in the first year: by 7% for 1–2 prescriptions, by 41% for 3–5 prescriptions, and by almost 50% for 6 or more prescriptions.
Antifungal agents were not associated with obesity.
Antibiotics are prescribed during an estimated 49 million pediatric outpatient visits per year in the United States. Between 2006 and 2008, more than 10 million prescriptions for antibiotics were written annually for children without clear indication, despite increased awareness of the societal risks of antibiotic resistance.
Scott et al state that obesity is a risk of antibiotic overuse that can be added to a list that includes dermatologic, allergic, and infectious complications; inflammatory bowel disease; and autoimmune conditions.
The authors say that antibiotics should be given to children who need them, but not without well-established indications—especially for children previously treated with antibiotics. The risk of subsequent obesity was greater in those children who had received 3 or more courses of antibiotics in their first 2 years of life.
Strengths of the study include its large sample size, near complete capture of lifetime antibiotic exposure, and adjustment for multiple factors. The authors conclude that their findings support the hypothesis that antibiotics progressively alter the composition and function of the gut microbiome, predisposing children to obesity as is seen in livestock and animal models.
Their findings link antibiotics to one of the most important and growing public health problems worldwide.