I've heard it before, and though widely noted, I don't think they had a way to explain it. Here's a WebMD link
People who underwent one of two stomach-reducing procedures were three to four times more likely to have their blood sugar drop to normal levels after one year of treatment compared with people who received intensive medical therapy alone.
Some people who had surgery got better so quickly that they were able to stop taking their diabetes medication before even leaving the hospital, says study head Philip Schauer, MD, director of the Bariatric and Metabolic Institute at the Cleveland Clinic.
In one recent study, 89% of people with type 2 diabetes who underwent gastric bypass surgery went into remission and 57% were still in remission after five years.
Reducing the amount of small intesting should be directly reducing the total load of gut bacteria, and perhaps the surgery is also changing the pH, shifting the balance of floura.