Do fat people have fat germs?

The Washington Post reported “a startling discovery that could lead to new ways to fight the obesity epidemic.” The Associated Press suggested: “Maybe it’s germs that are making you fat.” A Nature magazine Op-ed written by Matej Bajzer and Randy J. Seeley of the University of Cincinnati said: “This is a potentially revolutionary idea that could change our views of what causes obesity and how we depend on the bacteria that inhabit our gut.” And Jeffrey Gordon of Gordeon Lab, recently renamed the Center for Genome Sciences, at Washington University in St. Louis said: “For the first time, we see that there is a correlation between the microbial gut ecology and the obese state...That’s part of the pathology of obesity.”

Now, before you think that science has shown fat to be indicative of yet another diseased state, or that popping microbe-containing pills or special “probiotic” foods will make you slim, or that you might “catch” obesity, you’ll want to know what the research being reported actually found.

These news stories were based on a nine paragraph “Brief Communication” in this month’s Nature magazine. Researchers at Gordeon Lab wrote that when they tested the stool of ten people, the bacterial flora were different after the people had been dieting for a year and had lost weight, than their flora were before starting their diets. Of the trillions of bacteria and other minute bugs in the intestinal track that helps break down food and fight off infections, the proportions of two groups of bacteria, Firmicutes and Bacteroidetes, had changed after dieting. Bacteroidetes had increased from 3% to nearly 15% of the gut bacteria. So the people’s flora while they were fat were different than when they were thinner. It was also different from 5 thin people, although when asked, the researchers didn’t reveal the dieting status of these thin counterparts.

In their paper, the researchers concluded that this association between body weight and bacterial flora “indicates that manipulation of gut microbial communities could be another approach in the treatment of obesity.” They speculated that perhaps the bacteria were able to extract more energy from food, causing obesity, althought they didn’t know how many calories the microbes might account for and admitted it would be small.

Professor Boyd Swinburn, president of the Australian Society for the Study of Obesity in Melbourne, pointed out what is probably clear to you, too. This correlation between body weight and bacterial counts does not mean the bacteria caused the change in body weights, or caused obesity in the first place. “I think it’s totally wrong,” Professor Swinburn told the Australian News. “Gordon’s group showed only that dieting changed the balance of gut bugs, not the opposite as they claimed.”

The Center for Genome Sciences researchers will continue their Human Genome Project under a $1.45 million grant from W.M. Keck Foundation awarded them in February, 2005 to “develop new approaches to isolating, sequencing and analyzing the genomes of friendly bacteria that inhabit the intestine and identifying the natural metabolic products that they synthesize.”