The bacteria dwelling within a person's gut may help determine how big that gut appears from the outside, according to two new studies, giving credence to the idea that the obesity crisis may be partly due to microbes.

In both mice and humans, a group of Washington University researchers found, obesity can be linked to a relative increase in a group of gastrointestinal inhabitants better suited to grabbing food calories than a bacterial mix more characteristic of lean individuals, according to a report by Newsday's Bryn Nelson.

Scientists led by Jeffrey Gordon, director of Washington University's Center for Genome Sciences, used high-speed gene sequencing to examine the collective genome of two bacterial groups that dominate the human gut. The results showed that one group, known as the Firmicutes, are better able to digest complex carbohydrates and thus extract calories from food than the second group, collectively known as the Bacteroidetes.

The good news is that the Firmicutes seem to gain more of an upper hand as the microbes' hosts gain extra weight.

Check out Bryn's full article and make sure to go to the Nature journal site for some interesting video of scientists explaining gut flora and it's influence on our body weight.

-- Amanda Barrett, amNY.com