Gastric Bypass Surgery Reduces Blood Pressure

A recently presented doctoral thesis has found that gastric bypass surgery for obesity also markedly reduces blood pressure (BP) by adjusting the production of urine after eating or drinking.

The thesis by a researcher at the Sahlgrenska Academy (Gothenburg, Sweden) includes a study of 1,750 patients who underwent one of two types of obesity operations – gastric bypass or gastric banding; the results show that the elimination of urine increased after gastric bypass surgery. This is because the kidneys play an important role in the regulation of blood pressure by adjusting the production of urine after food and liquid consumption, so that the composition of bodily fluids and the blood does not vary too much.

After ten years, the researcher found that the decreased BP following gastric bypass was not related to the reduced weight, and was markedly larger than after gastric banding. This can be explained by the fact that food and drink no longer come into contact with the upper part of the digestive tract, thus breaking the link between this part of the digestive system and the kidneys. An unexpected finding was that consumption of salty food increased after gastric bypass surgery, even though BP went down. The researcher suggests that this is because the procedure also bypasses a link between the upper digestive tract and the brain, which is important for suppressing appetite for salt.

“We saw a long-term reduction in blood pressure after gastric bypass surgery, which could also be directly linked to the increase in patient's daily amount of urine after the operation,” said thesis author Peter Hallersund, PhD. “The gastric bypass probably reduces blood pressure in the same way as diuretic blood pressure medication.”

Gastric bypass involves the disconnecting of the stomach and part of the small intestine from the digestive system, so that food goes directly from the esophagus into the small intestine. The surgery significantly reduces appetite, partly through an increase in appetite-suppressing intestinal hormones as well as by causing the digestion to become less effective. On average, 75% of the excess weight disappears, and in many patients stays off.

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