Are Intestinal Bacteria Making Us Fat?

Could it be that it's not just genes, diet and exercise that determine our amount of body fat? Jeffrey Gordon and Fredrik Backhed -- microbiologists at the Washington University School of Medicine in St. Louis -- think so. Their experiments with mice show them that certain types of gut bacteria secrete a chemical that messes with the hormone responsible for fat storage.

Even when fed a "moderate" diet, mice with a normal mix of intestinal bacteria got fat. Gordon and Backhed compared this group with mice raised & kept in a germ-free environment. Despite having a higher-calorie diet than the normal mice, these isolated mice actually had 40+% less fat -- until they were exposed to the gut bacteria found in the fat mice. Then they, too, gained weight.

"Killing off the gut bacteria is not a viable option," concludes an article in Discovery Magazine "it would trigger opportunistic infections long before it would yield meaningful weight loss—but Gordon is targeting the fat-promoting hormone itself in hopes of developing a better diet drug." [More detail on the study is here.]

Dr. Gordon and a team of WU researchers are also using a $1.45 million grant to sequence and analyze the genomes of friendly (probiotic) bacteria that live in human intestines. Says Gordon, "Our objective is to understand how the human body functions as a carefully woven fabric of interacting species. Ultimately, such understanding promises to provide new ways of fortifying health and preventing or treating a variety of diseases both inside and outside of the gastrointestinal tract."