June 21, 2010|By Amber Dance, Special to the Los Angeles Times
Something in your gut could be making you fat — and it isn't just last night's pizza.
The vast, diverse community of microbes inhabiting the intestines, scientists are finding, can influence metabolism and weight.
Between 10 trillion and 100 trillion microbes, mainly bacteria, dwell in a person's colon and small intestine. They function together almost like another of the body's organs, influencing, among other things, how many calories we extract from our food and whether we make or burn fat. Researchers have discovered significant links between gut bacteria and weight and metabolism in mice — and are starting to find similar associations in people.
The story in humans is far from certain, though, and scientists say it's too soon to concoct microbe-filled "stay-slim" beverages — a fact that has not prevented some companies from promoting their bacteria-laden products as helpful for weight loss.
Bacteria that draw the maximum calories from our food would have been useful to our hunter-gatherer ancestors but are less beneficial for modern people eating an American fast-food diet. In addition to our ready access to high-calorie eats, the bacteria we carry around have changed, says Andrew Gewirtz, an immunologist at Emory University in Atlanta, through antibiotic use, improved hygiene and cleanliness in the food supply.
This, he believes, could be one environmental cause for obesity and related conditions such as diabetes.
On the whole, our gut bacteria are beneficial, says Ruth Ley, a microbial ecologist at Cornell University in Ithaca, N.Y. They prevent disease-causing bacteria from taking hold in our body simply by filling up all the available space. And they help us digest foods, such as some starches, that we cannot break down ourselves, producing vitamins and energy sources we can use.
"You might just generally be sicklier without them," Ley says.
Babies are born bacteria-free but start to pick up bacteria during and after birth. Infants mostly collect bacteria from their mothers and others around them; in a sense, the gut community is inherited from family members. If the gut-obesity theory proved correct, that would suggest obesity risk could be passed along with them.
"If a person has changes in their gut bacteria — and that could be due to anything, to diet, to antibiotic use — if that person has kids, then they can transfer those gut bacteria and maybe transfer the problem," Gewirtz says.
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http://articles.latimes.com/2010/jun/21 ... s-20100621
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