EATEN too many pies? Blame the microbes in your gut – they may be influencing how much you eat.

In 2006, biologists found that the types of bacteria in the guts of obese rats differed from those in non-obese rats. To find out more, Mihai Covasa and his colleagues at the French National Institute for Agricultural Research (INRA) in Paris swapped gut bacteria between obesity-prone and obesity-resistant rats.

The obesity-resistant rodents proceeded to eat more and pile on the pounds. They also developed gut hormone levels typical of obesity-prone rodents.

These rats are a good model for human obesity – people, too, are either resistant or vulnerable to the condition. Understanding the gut flora associated with it may offer ways to help control food intake, Covasa said this week at the Experimental Biology 2012 meeting in San Diego, California.