People who live in colder climates tend to have more of the gut microbes associated with obesity, a new study suggests.

Researchers found that people living farther north, in generally colder locales, have more of the bacterial group Firmicutes and fewer of the group Bacteriodes within their guts.

Previous research has shown that people with more Firmicutes bacteria tended to be heavier, while people with leaner bodies had more Bacteriodes. (The new study didn’t have information on subjects’ body mass indexes, and so couldn’t directly tie the bacterial gut composition with obesity.)

Still, the new findings support the hypothesis that certain obesity-associated microbial communities are “too good at digesting food,” meaning they break food down in a way that leaves more calories available for a person’s body to use, said study co-author Taichi Suzuki, a doctoral candidate in integrative biology at the University of California, Berkeley.

However, the study found an association, not a causal relationship, between gut bacteria and geography. As a result, it’s hard to say whether genetic differences, dietary changes or some other mechanism is at play, Suzuki told Live Science.

Past work had suggested that people have adapted to colder climates by packing on extra pounds that act as insulation, Suzuki said. For instance, some studies have found that Inuits tend to be heavier than African tribesmen, he said.

But the relationship between cold and weight isn’t clear-cut. For instance, spending time in the cold increases caloric expenditure. And other studies show that shivering triggers similar muscle responses as exercise.

Live Up North? Your Gut May Have More ‘Fat’ Microbes – Yahoo News