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Why Gastric Bypass Surgery Cures Diabetes

In most cases gastric bypass surgery (GBS) produces immediate and long lasting remission of type 2 diabetes. In this article, I explain the reasons for this and the rationale for a much less drastic nutritional cure for diabetes. Although not mentioned in polite conversation, everyone has increased gas (flatus) after gastric bypass surgery from fermentation of food in the hingut which is likely the key to the remarkable diabetes cure.

How Diabetes Became a Global Epidemic

In 2004, Gross et al found the best explanation for the epidemic of diabetes during the 20th century was increasing high glycemic carbs at the same time as decreasing fibre intake. This notion is reinforced by gastric bypass research providing insight into the cause of diabetes and why a low carb, high fiber diet would be effective for prevention and treatment of diabetes.

How Gastric Bypass Surgery Cures Diabetes

Within 1 week of GBS blood glucose and insulin levels return to normal before any weight loss has taken place, a remission that cannot be explained by energy restriction alone as surgery that simply restricts energy intake is less effective for weight loss or hunger suppression. Plus, only half as many patients receiving only restrictive surgery achieve a long term cure of diabetes. So bypassing the duodenum to direct undigested food into the lower intestine has additional important effects on energy metabolism. Two theories have been proposed to explain this: a substance produced from the foregut in response to food promotes diabetes while a substance from the hindgut in response to food prevents it.

Figure 1. The Two Most Common Bariatric Surgeries in the United States

The first is a Roux-en-Y gastric bypass (RYGB) in which a small pouch is created just beneath the esophagus that is not in contact with the rest of the stomach. The jejunum is anastomosed to this small pouch so that ingested food ‘‘bypasses’’ the remnant stomach and upper small intestine and flows directly into the jejunum. The second is a vertical sleeve gastrectomy (VSG) where roughly 80% of the stomach along the greater curvature is removed, turning the pouch of the stomach into a ‘‘sleeve.’’

Figure 2. Detailed diagram of the RYGB, left shows how food avoids digestive enzymes (that enter just after the pylorus) and bypasses much of the small intestine to enter the hind gut largely undigested.

In the foregut, glucose in the duodenum stimulates production of a hormone (GIP or Gastric Insulinotropic Peptide) that may be responsible for the abnormaly high levels of insulin characteristic of diabetes. Food bypassing the duodenum cannot stimulate GIP as the K cells that produce it are located in the foregut only. GIP levels progressively decrease after RYGB and may contribute to the prompt reversal of hyperinsulinemia after RYGB.

The hindgut theory is explained by dramatically increased production of hormones (GLP1) that regulate glucose metabolism and appetite (PYY) from hind gut lining L cells in response to undigested food and fermentation products, particularly short chain fatty acids (SCFA). Bypassing digestion provides a huge increase in food for hind gut bacteria multiplication and increased fermentation, the importance of this is evidenced by the fact that virtually all gastric bypass patients have increased intestinal gas production i.e. flatulence, bloating, rumbling feelings and noises, etc. Food consumed after RYGB is poorly digested and fermented by the gut bacteria producing hydrogen, organic gases and carbon dioxide along with SCFA’s which are important intestinal nutrients as well as signaling molecules that interact with SCFA receptors present at the surface of numerous cell types of the body including immune cells that regulate inflammation.

A Simpler Solution to Diabetes: The High Fiber, Low Carb Diet

To simulate the dramatic effects of RYGB with diet it is necessary to avoid high levels of glucose in the duodenum as well as rapid spikes in blood glucose, both contributing to chronic hyperinsulinemia (pre-diabetes). At the same time the hind gut response can be simulated by fibre for the all-important fermentation products that sustain the integrity of intestinal cells and stimulate production of hormones that regulate glucose metabolism, pancreatic function and appetite.

One way or another if you want avoid diabetes you take your choice--- gastric bypass surgery or avoid carbs and up your fibre but either way, seriously no gas no gain.


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