Gut microbes may make you fat
Bacteria in your gut may determine whether you are skinny or obese, according to scientists who say that food, exercise and genetics may not be the only things to influence body weight.
US scientists have discovered that levels of two types of good bacteria in the gut that help to break down foods are different in obese and lean people and mice.
The finding, reported today in the journal Nature, could lead to a better understanding of why some people may be prone to obesity and help find new ways of preventing or treating it.
"Our gut microbial structure should be considered when understanding the elements that might regulate our energy balance and may predispose us to obesity," says Professor Jeffrey Gordon, of the Washington University School of Medicine in St Louis.
"There is something very startling about the amount of fat you have and the structure of your gut microbial community," he adds.
There are trillions of bacteria in the gastrointestinal tract, but two groups called the bacteroidetes and the firmicutes are the most dominant and their proportion varies in lean and obese mice and humans.
The scientists found that the proportion of bacteroidetes bacteria is lower in obese mice and people than in lean people.
But when Gordon and his team studied 12 obese people who followed low-calorie diets for a year, they found their levels of bacteroidetes rose as their weight decreased.
"They increased as the weight is lost and in proportion to the amount of weight loss," says Gordon.
The results suggest that there may be a microbial component to obesity. But scientists do not yet know if people start out with lower levels of bacteroidetes or firmicutes that may make them prone to obesity.
"These are things we are exploring now. What are the signals between the amount of fat and different groups of bacteria that exist in the gut," says Gordon.
University of Cincinnati researchers, writing in an accompanying commentary in the journal, say:
"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. But a great deal remains poorly understood."