Ongoing research into the role of the microbiome (bacteria in the gut) in human wellbeing is at a very early stage. But the frequency of media headlines linking gut bacteria to health is growing. As with all areas of science, claims which have not been verified in clinical trials and subsequently replicated must be treated with caution. Nevertheless the evidence of a relationship between gut microbiome diversity and obesity has been repeatedly demonstrated in mice.
The microbiome is a term used to describe all of the genetic material of a microbiota, the entire range of microorganisms present in a particular context, in this case the human gut.
There have been a number of studies which show that obese mice tend to have fewer different types of gut bacteria than thin mice. The thinking is that a greater range of gut bacteria is likely to positively influence the way that the digestive system breaks down food. Having more (types of) bacteria is linked to efficient processing of what we eat, with the results of a tendency not to be obese. Recent research reported in The Independent looked at the weight gained by 1,632 female twins over nine years. The study calculated that only 41% of the weight increase could be explained by genetic factors.
On closer inspection it was estimated that becoming slimmer or maintaining the same weight was connected to the consumption of dietary fibre (typically found in whole grains, fruit and vegetables). The study also discovered that the women who had gained weight, had a lower diversity of gut bacteria. These findings were in line with similar studies with mice. Although not yet conclusive the overall evidence linking the shape of our body and the composition of our microbiome is growing.