Gastric bypass surgery permanently changes the make-up of microbial communities in the gut, new research shows.
Previous studies – for instance, one led by Husen Zhang of Arizona State University – established that obesity is associated with reduced diversity of gut microbe species. This has a negative impact on health, because the gut microbiota is critical for efficient digestion.
The new study, led by Zehra Esra Ilhan and Rosa Krajmalnik-Brown, also of Arizona State University, set out to determine the effects on microbial diversity of two popular weight-loss procedures: Roux-en-Y gastric bypass (RYGB), and laparoscopic adjustable gastric banding (LAGB).
Of the two, RYGB is the more aggressive intervention, and is irreversible.
The team discovered that after weight-loss prompted by the bypass surgery, most patients gut microbiota underwent profound change, resulting in a bacterial ecology that was different to those of both obese and normal-weight people.
The post-surgery biota was highly diverse – a sign of an efficient system – and the change was permanent.
“This is one of the first studies to show that anatomically different surgeries with different success rates have different microbiome and microbiome-related outcomes,” says Ilhan.
Krajmalnik-Brown adds: “Diversity is good because of what we call functional redundancy. If you have 10 workers that can do the same job, when one of them gets sick, the job still gets done.”
In separate studies, Krajmalnik-Brown and colleagues have previously linked poor quality gut microbiomes to a surprisingly wide array of conditions, including inflammatory bowel disease, ulcerative colitis and even autism.
Numerous studies have identified gastric bypass surgery as an effective long-term weight-loss strategy for obese and morbidly obese people. However, it doesn’t work in every case, with some patients continuing to gain weight after the operation.
Ilhan suspects the failure of the surgery might reflect a failure of the gut microbiome to flourish.
She suggests that further research might find a way to avoid the invasive and risky procedure, replacing it with a bacteria-friendly infusion.
“A probiotic that would replace surgery would be great,” she says.
“Another positive outcome would be if we can find a microbial biomarker that will identify the best candidates for surgery and sustained weight loss.”
Andrew Masterson is a former editor of Cosmos.