A newly published study in JAMA Pediatrics indicates that children who had had four or more courses of antibiotics by age two were at a 10% higher risk of being obese by age five. Researchers from the University of Pennsylvania and the Bloomberg School of Public Health examined the records of more than 64,500 children between 2011 and 2013. The children were followed until the age of five. In addition to show a link between antibiotic use and childhood obesity the study also indicated that the type of antibiotic also appeared to make a difference. Children who were given repeated doses of broad spectrum antibiotics, that target a variety of microbes, were nearly twice as likely to become obese when compared to those who received the narrow spectrum varieties aimed at specific species. The researchers corrected their data to take into account variations in obesity risks associated with ethnic and socioeconomic factors. They also discounted the possibility that other medications given alongside antibiotics might be responsible for the weight gain.
The study confirms that the microbial gut population plays a role in obesity and that antibiotics can alter its composition to foster weight gains. A notion supported by animal studies carried out by Dr Blaser of New York University in New York and published last August in the prestigious journal Cell. In one study three groups of mice were followed. One group was treated with low doses of penicillin in the womb. A second group received the same dose after weaning. The third did not receive any penicillin. Both groups that received penicillin showed an increase in fat mass when compared to mice not treated with antibiotic. The interesting feature though, was that the increase was higher in the group receiving penicillin stating in the womb. This suggests that mice are more prone to weight gain when receiving antibiotics early in life.
Another experiment was the carried out by determine if the weight gain was caused by the antibiotic or by altered bacterial population in the gut. Bacteria were transferred from penicillin treated mice to specially bred germ-free mice and antibiotic free mice. The researchers discovered that mice receiving bacteria from the antibiotic-treated donors became fatter than the germ-free mice inoculated with bacteria from untreated donors. This showed, according to the researchers, that the altered microbes are driving the obesity effects not the antibiotics. It also contradicted the theory that antibiotics in farming causes weight gain in animals by reducing total microbial population and therefore the competition for nutrients.
It has been known for decades that over prescription of antibiotics could lead to the growth of resistant bacteria. Now here is another potential health effect to consider. It suggests that doctors should, as much as possible, reduce restrict their prescriptions of antibiotics in children and more specifically of the broad spectrum type.