In an animal study that may have human implications, mice given antibiotics when young showed a greater likelihood of becoming obese as adults, scientists say.
Early exposure to antibiotics can cause disruption to gut bacteria with a permanent effect on metabolism, possibly increasing the risk of obesity later in life, they found.
"We found that when you perturb gut microbes early in life among mice and then stop the antibiotics, the microbes normalize but the effects on host metabolism are permanent," study lead author Dr. Martin Blaser, a microbiology professor at NYU School of Medicine, says.
A metabolic rate permanently slowed down could increase the risk of obesity because the body can burn off calories as quickly, the researchers said.
"This supports the idea of a developmental window in which microbes participate," Blaser says. "It's a novel concept, and we're providing direct evidence for it."
However, the researchers stress, much more evidence would be needed before a correlation between early antibiotic use and human obesity could be suggested.
Their results in the mice study should not necessarily deter doctors from prescribing antibiotic treatments in young children when appropriate and necessary, they said.
They worked with three groups of mice in their study, they said. One group was exposed to small doses of penicillin during the final days of pregnancy and on through their lives; another group was put on continuous penicillin doses after being weaned from their mothers; and a third group was give no penicillin at any time in their lives.
The results were clear; mice that received antibiotics became obese.
In a subsequent test, microbiota taken from mice given antibiotics was transferred to mice not exposed; they also became obese, the researchers said.
This showed that gut bacteria by itself could bring about a chance in body configuration, they said.
Though hesitant to apply such findings to possible human impacts, the researchers said their results could be reason to think about antibiotics for children.
"For children, we think there is an implication that early-in-life antibiotics could have some costs that were previously unknown," says Blaser. "It is further stimulus for more judicious use of antibiotics in children."
Many children are still being treated for ear infections and upper respiratory conditions caused by viruses that have become resistant to antibiotics, Blaser notes.
That may be sufficient reason to think twice about such antibiotic treatment in young children, he says.
"So as evidence accumulates ... doctors and patients and parents may say, OK, let's wait a few days and see how this ear infection is going to go," he says. "Most of the time it gets better by itself."
