Stumbling out of a holiday food haze? Feeling fat? Wondering what separates you and your good intentions about your waistline from those who seem perpetually and effortlessly svelte? Well, maybe-- just maybe-- it's less your inability to resist Christmas cookies and your little used gym membership than the bacteria packed into your gut.
According to two studies being published in Thursday's issue of the journal Nature, both obese mice and people had more of one type of bacteria and less of another kind.
A "microbial component" appears to contribute to obesity, said study lead author Jeffrey Gordon, director of Washington University's Center for Genome Sciences.
Obese humans and mice had a lower percentage of a family of bacteria called Bacteroidetes and more of a type of bacteria called Firmicutes, Gordon and his colleagues found.
The researchers aren't sure if more Firmicutes makes you fat or if people who are obese grow more of that type of bacteria.
But growing evidence of this link gives scientists a potentially new and still distant way of fighting obesity: Change the bacteria in the intestines and stomach. It also may lead to a way of fighting malnutrition in the developing world.
"We are getting more and more evidence to show that obesity isn't what we thought it used to be," said Nikhil Dhurandhar, a professor of infection and obesity at Louisiana State University's Pennington Biomedical Research Center.
"It isn't just (that) you're eating too much and you're lazy."
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Of course, until scientists develop a cereal called Bacteroidetes Flakes for your breakfast, it's probably best to put down the cookie and step onto the treadmill.