But the researchers uncovered a new piece of the puzzle that could actually be quite useful. It turns out that the intestinal bacteria associated with obesity break down certain flavonoids that we get from our diets faster than lean-associated bacteria do. As a result, obese and previously obese mice have lower levels of these flavonoids in their systems and this reduces the rate at which they oxidize fat.
The enhanced degradation of these flavonoids by gut bacteria could explain—at least in part—why people who have lost weight burn fewer calories than similarly sized people who have never been overweight. Sure enough, when the researchers transferred bacteria from the intestines of lean mice into the intestines of yo-yo dieter mice, the levels of flavonoids in their guts rose, along with their metabolisms.
Excerpted from quickanddirtytips.com