Bacteria get a bad name, but the ones in your gut help you digest the foods you like and need.

The number of microbiota in our intestines is mind boggling: would you guess 100 trillion? And there are up to one thousand species.

But we're learning that they not only digest food, some are really good at helping the body produce and store fat.

Meaning, certain types of bacteria in our intestines may be contributing to obesity. What a connection!

We knew bacterial colonization of the gut increases glucose absorption, which stimulates the liver to create fat. Bacterial fermentation in the gut also supplies short chain fatty acids that are absorbed and also contribute to fat.

This led scientists to question whether certain species of gut bacteria are associated with obesity?

During the past 20 years, obesity in the U.S. has increased dramatically. In 2008, only Colorado had an obesity rate of less than 20 percent, while the rate in 32 states was more than 25 percent.

In a recent study, researchers compared the gut microbiota of lean and genetically obese mice. They did the same with human volunteers.

The results showed obesity is connected to changes in the relative abundance of two dominant bacterias, the Bacteroidetes and the Firmicutes.

They found that the obese microbiome are extremely good at harvesting energy from the diet.

Plus – this trait is transmissible, which means when a germ free mouse is colonized with 'obese microbiota' it ends up with significantly greater body fat than a mouse colonized with a lean microbiota.

This shows the bacteria in our gut are another genetic factor in obesity.

More importantly, it shows we may be able to change the makeup of the bacteria in our gut and hopefully help the many Americans who are obese or headed that way.