Do the Bugs in Our Gut Affect Our Weight?

Although genes affect body weight, the growing obesity epidemic is clearly fueled primarily by environmental factors. The oft-cited villains are cheap, calorie-dense foods and inactivity. Researchers have fingered another novel potential villain: highly efficient gut bugs.

The trillions of bacteria in our gut help break down food, particularly polysaccharides, into digestible pieces, thereby affecting the amount of energy we can harvest from food. About 90% of our gut bugs fall into one of two divisions — Bacteroidetes and Firmicutes. Firmicutes generate more harvestable energy than Bacteroidetes.

A Washington University research team found more Firmicutes in the gut flora of obese mice than in normal-weight mice; when gut flora from obese mi…