Are antibiotics making you fat?

Listen to any TV commercial for a new drug and you'll hear a litany of bizarre side effects — amnesia, hallucinations, nightmares, blue urine and a furry-feeling tongue, just to name a few. But few of these lists include obesity, and overdosing on antibiotics, according to an article published in the magazine New Scientist, could be a major trigger for obesity.

People who overuse antibiotics have lower levels of good bacteria in their guts, and those good bacteria have been found to help prevent everything from cancer to obesity. A number of studies on mice have found that mice fed antibiotics at levels comparable to those given to farm animals are much heavier than mice fed no antibiotics at all — which isn't surprising, considering that antibiotics are often used to speed growth and fatten up animals for slaughter.

But what is concerning are the studies of antibiotics fed to mice at levels similar to what children receive when they get infections. In one study, microbiologist Martin Blaser, of New York University, fed mice short courses of antibiotics similar to those that children receive. Compared to the non-drugged mice, the antibiotic-fed mice had lower levels of T-cells, which regulate the body's immune response. Obesity has been associated with low levels of these T-cells...