Is weight loss surgery altering gut bacteria?

Long-term changes to the composition of bacteria in the gut could be caused by bariatric surgery, a recent Swedish study suggests. Bacteria in the gut, known as the microbiome, are known to affect weight within individuals and this study observed that the change in the microbiome after bariatric surgery was such that fat deposition was reduced in the long-term, suggesting that a composition change plays a direct role in weight loss after surgery.

Researchers analysed the microbiomes of women nearly a decade after they underwent bariatric surgery. Half of the women underwent Roux-en-Y gastric bypass (RYGB) – where a small pouch is created at the top of stomach and connected to the small intestine – whilst the other half underwent vertical banded gastroplasty (VBG) – where the stomach is made smaller with bands and staples. The women that underwent RYGB had more significant differences in their microbiomes compared to that of those who had VBG, and those who had no surgery. The researchers then transferred the bacteria to mice and found that they also put on less fat, supporting their theory. In particular they found that the abundance of 29 microbial genera differed significantly between RYGB and non-surgery patients. The differences with VBG and non-surgery were not significant.

The research highlights the potential importance of probiotics in the treatment of obesity as this is one of the first studies that shows the change in microbiomes to be long-lasting.

Read more