Research, published in Proceedings of the National Academy of Sciences, showed that a broth containing a single species of bacteria could dramatically alter the health of obese mice. It is thought to change the gut lining and the way food is absorbed.
Similar tests now need to be take place in people to see if the same bacteria can be used to shed the pounds. The human body is teeming with bacteria - the tiny organisms outnumber human cells in the body 10 to one. And there is growing evidence that this collection of bacteria or "microbiome" affects health.
Studies have shown differences between the types and numbers of bacteria in the guts of lean and obese people. Meanwhile gastric bypass operations have been shown to change the balance of bacteria in the gut.
Researchers at the Catholic University of Louvain, in Belgium, worked with a single species of bacteria Akkermansia muciniphila. It normally makes up 3-5% of gut bacteria, but its levels fall in obesity. Mice on a high fat diet - which led them to put on two to three times more fat than normal, lean, mice - were fed the bacteria. The mice remained bigger than their lean cousins, but had lost around half of their extra weight despite no other changes to their diet. They also had lower levels of insulin resistance, a key symptom of Type-2 diabetes. Prof. Patrice Cani, from the Catholic University of Louvain, told the BBC: "Of course it is an improvement, we did not completely reverse the obesity, but it is a very strong decrease in the fat mass. "It is the first demonstration that there is a direct link between one specific species and improving metabolism."