The belly of the beasts

After weight-loss surgery the gut microbiome can fail to flourish. ANDREW MASTERSON reports.

Gastric bypass surgery permanently changes the make-up of microbial communities in the gut, new research shows. Previous studies have established that obesity is linked to reduced diversity of gut microbe species – which has a negative impact on health, because the bacteria in our bellies is critical for efficient digestion.

The new study, led by Zehra Esra Ilhan and Rosa Krajmalnik-brown of Arizona State University, in the US, 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). 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.

The new bacterial ecology was different to those of both obese and normal-weight people, but it was also highly diverse – a sign of an efficient system. “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,” KrajmalnikBrown notes.

Gastric bypass surgery is 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 this 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. The research was published in The ISMA Journal.