Obesity has become a worldwide epidemic, and fat-busting, weight loss programs are booming. But what if obesity was not related entirely to how many calories you eat, or how much exercise you do? It may sound crazy, but researchers at Washington University School of Medicine in St. Louis (WU) now believe that obesity may come down to the kinds of bugs living in our gut. While many people maintain their weight using the simple equation of eating lesser or equal amounts of calories relative to what they expend, two studies, published in the journal Nature, have shown that not all guts are equal. "Our studies imply that differences in our gut microbial ecology may determine how many calories we are able to extract and absorb from our diet and deposit in our fat cells," says WU's Jeffrey Gordon.
Through gene sequencing, the researchers showed that certain microbial communities harvest calories as they pass through the gut. This means that two people eating identical plates of food will not necessarily absorb the same amount of calories. "The differences don't have to be great, but over the course of a year the effects can add up," says Gordon.
There are many friendly microbes that live in the intestine, which help break down nutrients to extract calories to store them as fat. The researchers focused on the two major groups of bacteria known as the Bacteroidetes and the Firmicutes, which make up 90 percent of the microbes in humans and mice. The two studies showed that both obese humans and obese mice had 50 percent fewer Bacteroidetes and more Firmicutes.
The human trial was interesting because it found that irrespective of how subjects lost weight, the numbers of Bacteroidetes increased and the abundance of Firmicutes decreased. The researchers also found that they could increase a mouse's propensity for obesity by manipulating the balance of Bacteroidetes and Firmicutes in the mouse's guts, prompting Gordon to consider whether: "Some adults are predisposed to obesity because they 'start out' with fewer Bacteroidetes and more Firmicutes in their guts."
Source: Washington University School of Medicine
