The key to losing weight may be in your gut

Scientists at Washington University in St. Louis say different kinds of bacteria that live inside the gut can help spur obesity or protect against it. The researchers transplanted intestinal germs from fat or skinny people into mice, and watched the rodents change. And whether or not the good germs could move in and do their job was determined by what they ate.

The report in the Journal Science raises the possibility of one day turning gut bacteria into personalized fat-fighting therapies. And it may also help explain why some people have a harder time losing weight than others do.

Clearly, what you eat and how much you move are key to how much you weigh. But are those bacterial differences a contributing cause of obesity, rather than simply the result of it? If so, which bugs are to blame, and might it be possible to switch out the bad actors?