Gut bacteria can influence our behavior—and understanding the incredible diversity of the human microbiome may help us solve our obesity problem.
In 2006, Jeffrey Gordon, a microbiologist at Washington University School of Medicine, was looking into the microbacteria found in our guts. He was particularly interested in the species found in the intestines of obese mice and people. He later wrote in Nature that the array of microbes he found appeared to differ between the obese and their lean counterparts, which could have vast implications for combating obesity.
When you look inside our bodies, we are truly "superorganisms" of creatures working together. Microbial cells outnumbers human cells by a factor of 10 and there are150 times as many microbe genes as human genes. This microbiome establishes itself in the first two years of our life and persists despite the onslaught of French fries, Cokes, or carrots. As Robert Kolter explained at last month’s Knight Science Journalism Food Boot Camp, the diversity of the microbiome is remarkable. If you took the 20 most abundant species in the guts of you and your best friend, chances are there would be little overlap.
Our incredibly unique microbiome determines how our bodies absorb nutrients and ward off harmful microorganisms in the foods we eat. While it may play a key role in regulating body weight, since there’s so much diversity, discerning beneficial species has been difficult. This is especially true because, for many years, microbial research has focused on pathogens. Not only is it hard to sift the music from the noise, but it’s far more difficult to take that and then legislate your stomach’s unseeable life. As Kolter said, “To say we’re going to make a law that people can’t eat fat is wrong.”
How, then, do we go about addressing obesity? Part of the solution may lie in the gradual unraveling of the microbiome—and possibly altering the species living within our guts.
In this month's Science magazine, Elizabeth Pennisi writes about research on low-dose antibiotics in animal feed, which may be throwing off the balance of microbial life in our guts. Another more recent study suggests gut bacteria may even influence behavior and thought, as Mo wrote on the blog Neurophilosophy. But, Pennisi says, “it remains difficult to determine whether changes in gut microbes drive or contribute to obesity or whether the excess weight itself triggers those changes.” (So far, scientists have found connections between certain kinds of microbial life and obesity, although Kolter suggested, “More recent experiments indicate causality.”)
All of which goes to show the absolute wonder within our bodies, the incredibly complex roots of obesity, and the importance of limiting the unnecessary use of antibiotics. Clearly, changing our guts alone won't solve the entire problem. And if you think that merely eating a probiotic yogurt will help shed some pounds, remember, it usually only contains two or three species—and our understanding of beneficial microbes, for better or worse, suggests that the future of probiotic therapies will have to be a lot more complex than that.
Infographic via James Aubundis/The Boston Globe.