PALM BEACH, FLA. — Gastric bypass surgery does more than just cause weight loss. It produces rapid improvements in glucose tolerance, blood pressure, lipid levels, diabetes, and the risk of coronary heart disease, Dr. Alfonso Torquati said at the annual meeting of the Southern Surgical Association.
“We know that weight loss does not lead to the change in coronary heart disease risk. We think that bariatric surgery is metabolic. It bypasses the duodenum and changes the way that glucose and lipid metabolism work,” said Dr. Torquati, a surgeon at Vanderbilt University, Nashville, Tenn.
He and his associates assessed the effect of gastric bypass surgery on coronary heart disease (CHD) risk by calculating the Framingham risk score for 500 consecutive Vanderbilt patients just prior to surgery and again 1 year later.
The analysis showed that the average 10-year risk of CHD, based on the Framingham formula was 5.4% when calculated at baseline for the 500 patients who had bariatric surgery. One year after surgery, with complete follow-up of all 500 patients, the average 10-year risk of CHD was 2.7%, a statistically significant drop, reported Dr. William O. Richards, a coauthor and medical director of the Center for Surgical Weight Loss at Vanderbilt.
The cut in CHD risk was due to substantial improvements in systolic blood pressure and serum levels of low-density and high-density lipoprotein, as well as significant drops in the prevalence of type 2 diabetes and metabolic syndrome. The average weight loss in these patients during the first year after surgery was 69%.
Significant reductions in risk were seen in all patients, regardless of whether they had diabetes, regardless of their age or gender, and regardless of whether their baseline Framingham risk was low, intermediate, or high. Five-year follow-up data were available for 360 (72%) patients, and their actual rate of CHD was similar to their predicted rate calculated 1 year after surgery, Dr. Richards said.
“As the evidence grows, it becomes harder to ignore that bariatric surgery is a lifesaving intervention,” commented Dr. Eric DeMaria, vice chair of general surgery at Duke University, Durham, N.C.
“If weight loss alone does not drive the benefits of bariatric surgery, then what does?” he asked.
“We find that insulin resistance goes way down in the first weeks after surgery, especially at the level of the liver, before there is significant weight loss,” Dr. Torquati said. “You don't see the same changes with gastric binding, only with bypass,” suggesting that the metabolic changes are somehow linked to duodenal bypass, he said.
On the basis of these findings, it's reasonable to conduct a trial designed to test whether gastric bypass surgery can also produce beneficial changes in blood pressure, serum lipids, and diabetes in thinner patients, such as those with a body mass index of 30–35 kg/m2, Dr. Torquati said.