Closing a Tiny Hole After Bypass Surgery Helped Some Diabetes Patients
What was meant to stop acid reflux also caused weight loss and raised a new idea about the upper gut and blood sugar.
Huberman Lab · Best Tools for Gut Health & Weight Loss | Dr. Chris ThompsonIn 2003, Chris Thompson, then a young gastroenterology fellow, got a puzzle from a surgeon.
A patient who had undergone gastric bypass had come back with burning pain and reflux, weight regain, and diabetes that had disappeared after surgery and then returned. Gastric bypass creates a tiny new stomach pouch and leaves the old, larger stomach in place, so food skips the old stomach and the first stretch of small intestine.
The surgeon asked Thompson to look inside for an ulcer and find out what was causing the pain and heartburn. Thompson slid a scope through the mouth and found something else, a small hole, called a fistula, connecting the new pouch to the old stomach. He suspected acid made in the bypassed stomach was washing up through that opening.
Thompson had access to a new suturing device that could be passed through the mouth to place stitches without cutting open the abdomen. The device was approved, but no one had used it to close this kind of hole. He waited until he had joined the faculty a few months later, discussed it with the surgeon, explained the uncertainty to the patient, and got permission to try it.
The stitches were meant to stop reflux. The reflux did stop, but something larger happened. The patient started losing weight, and diabetes went away again almost immediately.
Thompson said he was flabbergasted, and wondered if it was coincidence and why closing such a small connection should matter so much. The question pushed him to study the hormones made by the gut, the chemical messengers that control hunger, fullness, and blood sugar.
He then tested the idea in more patients with the same hole. When he was able to close the fistula, 60% had their diabetes resolve. When the hole stayed open, none did. His account does not report how many patients were included, so it is hard to judge how firm that percentage is.
The possible lesson was that excluding the upper gut, not acid control, may be what changed blood sugar, and this is still a hypothesis. A colleague's rat study pointed the same way, with diabetes improving only when food was kept out of the upper small intestine. Whether the same mechanism explains the human cases, and what signal from that stretch of gut might matter, remains unknown.
Questions people ask
What does gastric bypass do to the stomach?
Surgeons create a small pouch at the top of the stomach, about the size of an egg, and connect it directly to the middle of the small intestine. Food goes into the pouch and skips most of the old stomach and the first part of the intestine. The old stomach stays in the body but no longer receives food.
What is a fistula in this context?
It is an abnormal opening that forms between two parts that should stay separate, here between the new pouch and the old stomach. Food and acid can pass through it, so the bypass partly stops working. Fistulas can develop after surgery as tissue heals and stretches.
Why would bypassing the upper gut affect diabetes so quickly?
The upper small intestine senses food and sends hormonal signals that affect insulin and blood sugar. Bypassing it, and delivering food faster to the lower intestine, increases hormones such as GLP-1 that lower glucose and reduce appetite. Researchers also think the upper gut may make a counter-signal that raises blood sugar, which exclusion removes.