As calorie counters and fitness fanatics have been demanding that we all eat right and exercise, scientists have been working on a different theory behind obesity, a bacterial one. How our bodies make and store fat, they hypothesized, could be affected by the bacteria that naturally exists in our digestive tracts. It's a plausible enough idea. If bacteria can cause other kinds of health conditions, it could be capable of causing obesity. A new study from China provides convincing evidence that this is exactly what's going on. It might show us the way to a cure, too.
The findings of the Chinese study are eight years in the making, though the most revealing experiment is wonderfully simple. After identifying a strain of human bacteria in the genus Enterobacter they believed to be linked to obesity, researchers fed it to a select group of mice and then put them on a high-fat diet and prevented them from exercising. In other words, they simulated the lifestyle of your average American. They put a control group of mice through the same diet and exercise routine but did not prepopulate their bellies with bacteria. And guess what happened. The mice that ate the bacteria first got fat.
The science behind the findings is also relatively simple. Enterobacter, scientists discovered, prevents the body from burning fat by manipulating the body's metabolism-controlling genes. Instead, the bacteria encourages the body to make more fat, fat that gets stores in guts, love handles, butts, thighs, and anywhere else you can think of. If you get rid of the bacteria, it stops encouraging fat retention. The team of researchers couldn't be more bullish about the discovery. "This is a very important phenomenon," said Professor Zhao Liping, a member of the research team from Shanghai Jiao Tong University. "It is the last missing piece of evidence bacteria causes obesity."
As Zhao suggests, scientists have stumbled across lots of clues linking bacteria to obesity in the past. A few years ago, a team of researchers, led by Washington University of St. Louis biologist Jeffrey Gordon, ran a similar experiment on mice, some with bacteria in their intestines and some that were kept completely bacteria-free, and found that those without tended to stay skinnier. They stopped short of identifying the specific bacteria that caused the weight gain in mice, though.
Earlier this year, there was a strong focus on trying to manipulate the bacterial make up of the digestive tract, perhaps through implants. Some doctors literally wanted to make fecal transplants — yes, that means what you think it means — standard practice as a way of treating obesity and other disorder.
Don't go get too excited about getting someone else's poop shoved up your butt just yet. There's a lot more research to be done before we can start eating fat-blocking Greek yogurt or taking obesity-avoiding probiotic pills. (Please, anything but the fecal transplant.) Zhao's team in Shanghai has successfully treated an obese man using a diet that inhibits the Enterobacter strain, which also makes patients take longer to feel full and causes insulin resistance. It'll probably take more testing and an epic joust between pharmaceutical companies and regulators before this treatment goes to market, though. If you're worried about getting fat in the meantime, eating lots of vegetables and hitting the gym every now and then can't hurt.
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