I came across this recent research by Liou and colleagues, published in the journal ‘Science’: http://stm.sciencemag.org/content/5/178/178ra41.
In Vivo research has identified that after a gastric bypass is performed, intestinal microbiota consequently changes. Now this is not something unexpected, as a restrictive surgery such as the Roux en y gastric bypass, by the very nature of the name bypasses the stomach, therefore all of the gastric secretions which would usually be utilised to digest food and prepare it for entering the intestines are not being used as usual. The extent to which absorption is affected is dependent on the type of gastric bypass (there are proximal, distal and ‘mini’ variations) and the length of small intestine used in reconstruction of the GI tract, however absorption will be affected to some degree. Therefore it is no surprise that intestinal microbiota undergoes a radical change post-operation.
However what was interesting and unique in this research is that the transferral of microbiota from a mouse which had had a gastric bypass into a mouse that hadn’t undergone surgery seemingly caused the mouse who had had no surgery to lose weight. The rate of weight loss was significant, with around 20% of the weight loss effects occurring simply by microbial transfer. The mice given the microbiota did not suffer any alteration in food intake, but their adiposity reduced, along with around 5% body weight.
As this is new research, it is still unclear whether the microbial and metabolic changes were directly linked, how the microbes may be altering metabolism and energy expenditure (is it through gut hormone signalling?), or indeed whether the same effect may be observed in humans, but this does seem promising for future research. Currently, fecal transplants are used for some illnesses which seemingly changes the gut microbiota aiding the illness to resolve, so perhaps this has some similar mechanism? Possibly, if it were found effective in humans, without negative consequences, a suitable probiotic containing the microbiota reflective of a patient undergone gastric bypass could be marketed for weight loss. Reducing the need for invasive, costly and nutritionally restrictive surgery.
(Thank you to http://thebypassedlife.com/where-are-vitamins-absorbed/ for the use of the above image)