Are Antibiotics in Food Making Us Fat?

Two new studies suggest antibiotics used to fatten cattle are fattening us, too.

I never knew this, but farmers have been giving cows and pigs low, steady doses of antibiotics for years because the drugs make the critters fatter. In fact, 80 percent of all antibiotics in the U.S. are consumed by farm animals. Now, published studies suggest that the worldwide epidemic of obesity may be due to antibiotics, too. Whoa.

In one study, the scientists fed mice the same low doses of antibiotics that ranchers provide to animals. The mice fattened up nicely, and the drug regimen altered the bacterial makeup of their “microbiomes,” which is scientist-ese for the stew of bacteria, viruses and such flowing through our bodies. In the other study, kids who’d been given antibiotics before the age of six months were found to have “small but consistent” increases in body mass. Even their genetic profiles were altered; the antibiotics produced “unusual activity” in genes governing the breakdown of carbs and the regulation of cholesterol.

These sorts of changes, says NYU microbiologist Marvin Blaser, could account for obesity: “Our microbiome is part of human physiology. We are doing things to change it, and those changes have consequences.” The bacteria in our bellies don’t just break food down; they also help regulate bodily functions.

Separate research has shown that microbes transplanted from the stomachs of obese mice into the stomachs of non-obese mice cause the latter to pack on pounds. Well, okay, maybe grams. The author of that study, Emory University’s Andrew Gerwitz, believes changes in the chemical makeup in our guts may actually be what drives us to eat unhealthy foods. And it might not just be antibiotics we take for illness that are affecting us; Gerwitz and Blaser are looking into whether the residual drugs we consume when we munch down on burgers and ribs are affecting us, too.

Meatless Mondays are looking better and better.