Are Antibiotics Making Americans Fat?

Intriguing new science points to a culprit other than all those bacon cheeseburgers.

(Photo: Lucas Jackson/Reuters)

Mar 13, 2014· 2 MIN READ
Jason Best is a regular contributor to TakePart who has worked for Gourmet and the Natural Resources Defense Council.

Are antibiotics making us fat? That was the headline-grabbing question posed last weekend in The New York Times by contributor Pagan Kennedy, and it’s generating a lot of buzz. The article, “The Fat Drug,” quickly topped the Times’ most-emailed list.

Public health researchers have long maintained that the primary cause of America’s obesity epidemic is the combination of our increasingly high-calorie diet (hello, Cheesecake Factory’s Oreo Dream Extreme Cheesecake) and an increasingly inactive lifestyle (there you are, couch). And most experts still maintain that. Yet a number of scientists believe there’s something else—or, really, a number of something elses—bringing its weight to bear.

In other words, if the recent research reported by Kennedy points to routine antibiotic use as a smoking gun, it is likely just one in the fusillade of causes behind America’s seemingly ever-expanding waistline.

That said, Kennedy’s article is fascinating, starting with the revelation that farmers didn’t start feeding antibiotics to their livestock to make the animals healthier but to make them fatter. Early research showed that chicks and piglets that were fed antibiotics put on significantly more weight than those that weren’t—it was initially only a side “benefit” that the animals could thus be crowded into more stifling and dirty conditions and not get sick. Voilà, the birth of the factory farm.

By the 1950s, as farmers clamored for more antibiotic “slurry” from drug companies (pretty much the industrial leftovers from the drug-making process), dubiously ethical experiments were already being conducted on people (kids in Guatemala; unwitting Navy recruits), and it turned out that humans also gained weight when fed a steady diet of antibiotics.

That’s very different from how people consume antibiotics today, and there are a couple important points to keep in mind—the sort that tend to get overlooked when headlines blare something like "Antibiotics Are Making Us Fat!" First, neither Kennedy nor the scientists studying the antibiotic-obesity link are suggesting that we’re consuming copious amounts of antibiotics via the meat and other food we eat. "By the time most meat reaches our table, it contains little or no antibiotics," Kennedy writes.

Rather, they’re addressing our exposure to antibiotics as medicine from childhood on, the penicillin or Zithromax prescription swallowed for every bout of strep throat or pesky ear infection—an average of one course of antibiotics per year for American kids, according to Kennedy.

Second, no one is saying we should stop taking antibiotics entirely. As Kennedy put it in a follow-up interview with NPR, “Antibiotics are terrific, lifesaving drugs. If you have an infection and your doctor tells you to take antibiotics, you should take them.”

Still, as health researchers began to unravel the connection between the many trillions of bacteria that call each of us home and our general health, it would seem that routinely carpet bombing our “microbiome” with antibiotics could have some unforeseen consequences, to say the least. For every “human” cell in your body—that is, a cell with your DNA—there are 10 bacteria cells, cells that antibiotics attack, scientists estimate. “You’re 10 times more bacteria than human” is how one researcher puts it.

Kennedy cites research being conducted at the lab of Martin J. Blaser at New York University, which has found that mice fed a high-calorie diet along with antibiotics gained more body fat than mice that ate the high-calorie diet alone. In female mice, the results were “dramatic.” They gained twice as much body fat. As Dr. Ilseung Cho, who works in Blaser’s lab, said on NPR, “Our studies suggest that intermittent use of antibiotics at a young age could lead to obesity.”

So what to do? The answer at this point is decidedly not to take yourself (or your kids) off prescribed antibiotics—the science is still to early for that.

But there’s more than enough science to merit stricter regulations on antibiotic use on farms, where routine drugging of livestock has been linked to the rise in antibiotic-resistant strains of salmonella, staph, and other nasty bugs. That could go a long way toward keeping us from having to take even more, ever stronger antibiotics.