The number of bacteria in your gut -- as well as the diversity of said bacteria -- could be tied to your weight, according to a new study.
A team of researchers from around the world found that people who are obese have fewer and less diverse gut bacteria than their leaner counterparts.
"We also see that if you belong to the group with less intestinal bacteria and have already developed obesity, you will also gain more weight over a number of years," study researcher Oluf Pederson, professor and scientific director at the University of Copenhagen's Faculty of Health and Medical Sciences, said in a statement. "We don't know what came first, the chicken or the egg, but one thing is certain: it is a vicious circle that poses a health threat."
Researchers noted that the gut bacteria makeup of people who are obese may be provoking mild inflammation, which could thereby raise the risk of chronic health conditions like heart disease and diabetes. (And of course, other research has suggested that some gut bacteria can actually turn a nutrient found in egg yolks and meat into a compound called TMAO, which clogs arteries and raises heart risks.)
"Even lean people who are poor in bacterial species have a higher risk of developing these pathologies," study researcher S. Dusko Ehrlich, of the INRA Research Centre of Jouy-en-Josas in France, told NPR.
The Nature study is based on genetic mapping of intestinal bacteria from 292 Danes, and also showed that about one in four people has 40 percent less gut bacteria than average, as well as a lower-than-average diversity of bacteria.
The study is the work of the MetaHIT team, which included scientists from elsewhere in Europe and China.
In another study also published in the same issue of Nature, French researchers found that overweight and obese people may be able to boost their gut bacteria numbers and diversity by changing their diets.
Previous research has suggested that dietary changes to gut bacteria could also affect the brain. A study of women in the journal Gastroenterology demonstrated that eating yogurt with probiotics (which contributes to healthy gut flora) affected the brain activity and engagement.