Bacteria living in your gut can make you fatter!

BBC News : 'Friendly' bacteria living in our digestive systems may be helping to make us fatter, say scientists.

Trillions of bugs live in the human gut, helping us break down food. A team from Washington University School of Medicine claim when one type is dominant, this may impact on how many calories we extract from our diet. Writing in the journal Nature, they described how they were able to make mice obese simply by adjusting the levels of certain types of bacteria.

They say it may be possible to treat obesity by doing the same to humans. Obesity is recognised as a major health threat in many Western countries, including the UK, where a recent study suggested its effects consumed 9% of the total NHS budget.

While eating too much is the obvious primary cause, scientists have been looking for other factors which might pre-dispose people to gain weight.

The Washington University team, led by Dr Jeffrey Gordon, has been looking at the levels of two types of bacteria normally found in the gut - the Bacteroidetes and the Firmicutes. They found that in obese people, the relative proportion of Bacteroidetes compared with Firmicutes was less - and a similar result was found in a strain of laboratory mice bred to be genetically obese.

Mice with no gut bacteria then had either Bacteroidetes or Firmicutes injected into their digestive systems, and while both groups then gained weight, the weight gain with Firmicutes was significantly higher.

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