The weight of the average American woman has gone up 20 pounds since the early 1970s. And women are twice as likely as men to have the chronic, low-grade digestive complaints that get lumped together as Irritable Bowel Syndrome. The belly of the American woman is letting us know something has gone very wrong. The scientific world has undergone a revolution in the way it understands the gastrointestinal tract, specifically the role played by the roughly one hundred trillion bacteria that live there. They’re called the “gut microbiome,” referring to their total package of genes, or the “microbiota,” referring to the organisms themselves. We’ve known for 20 years that the bacteria living in our colon break down the fiber we get from plant sources. What we’ve only just recently appreciated is that if the microbiota are not being properly attended to—if they’re not being fed enough plant fiber or if they’re being indiscriminately wiped out by overuse of antibiotics or if they’re damaged over time by excessive amounts of stress hormones—weight, digestion and the immune system can go haywire. In a landmark 2013 study published in the prestigious journal Nature, a French team tracked two groups of subjects, 169 obese people and 123 lean ones. The lean group had more bacteria at work in their guts and more different strains than their heavier counterparts. They were less likely to gain weight over the nine years of the study and less likely to develop the most common chronic diseases, such as heart disease and type 2 diabetes. MORE: The 26 Best Foods For A Happier, Healthier Gut Well, you might say, the lean group was just born lucky. But in a second study, 49 overweight subjects were put on a lower-calorie, higher-fiber diet for 6 weeks. Not only did they lose weight, but the community of bacteria in their guts also became more diverse; in other words, it more closely resembled the bacteria in the people who were naturally lean. Think about that. What the revolution in microbiology is telling us is that we can change the genes in our microbiome, and that will have an enormous effect on how we look and feel. Our nation’s weight problem may be a micro-obesity issue. MORE: 4 Easy Ways To Boost Gut Bacteria (And Why You’d Even Want To In The First Place)
