Fat keeps the body warm, so it stands to reason that people living far from the equator have more body fat. A new study says that could be because people who live farther North have more obesity-related microbes in their guts.
Researchers at UC Berkeley studied the proportions of two particular types of gut bacteria in stomachs around the world: Firmicutes and Bacteroidetes. Previous studies have shown that people with a lot of Firmicutes and very little Bacteroidetes are more likely to be obese.
Gut Bacteria, Hot and Cold
By gleaning medical data from half a dozen previous studies (1,020 healthy people living in 23 different locations) the researchers found that, in general, a person who lived more poleward hosted more obesity-related bacteria than their equatorial counterparts. Thus a Swedish person's microbiota, for instance, was higher in Firmicutes and lower in Bacteroidetes as compared to the gut of someone living in Malawi. This held true even after researchers controlled for other factors such as age, gender and some genetic factors, according to the study
published in Biology Letters.
The connection between geography and gut bacteria is not a clear cause and effect, though. The scientists can't say for sure that other factors like diet or unexamined genes aren't at play in shaping a given population's microbe population. However the findings add to the growing body of evidence that a person's weight is, at least in part, dictated by the bugs in their gut. Study coauthor Taichi Suzuki said
this is because of the way obesity-related bacteria breaks down food; they digest with extra efficiency, leaving the person's body with more calories at its disposal. One more reason to consider becoming a snowbird and flying South for the winter.
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