Diabetic and Cardiovascular Benefits of Bariatric Surgery Occur Even Prior to Weight Loss
Obesity is a major risk factor for diseases such as Type 2 Diabetes and heart disease. Once diets and lifestyle changes have failed, some people turn to bariatric surgery such as gastric bypass or gastric banding to bring their weight to within a normal range, thus reducing the risk of developing such conditions or to eliminate co-morbid disease symptoms.
Researchers are learning, however, that the benefits of weight loss surgery (WLS) in obese patients biologically begin prior to dropping the pounds. Two new studies have been released this week explaining the reduction in risk factors for diabetes and cardiovascular disease.
Researchers at the Imperial College London studied a total of 1006 patients who underwent one of three types of bariatric surgery – gastric bypass, sleeve gastrectomy, and gastric banding. Just over 200 of those patients had Type 2 diabetes. The patients were followed for an average of 23 months after surgery. The goal for the patients, aside from weight loss, was complete remission of their diabetes, defined as returning to normal measures of glucose metabolism without diabetic medication at least one year after surgery.
Nearly three-fourths of all patients (72%) saw a reduction in HbA1c, a marker of long-term blood glucose control. However, those who had the greatest blood sugar normalization were those who had had gastric bypass surgery. A total of 40.6% patients having the stomach-stapling procedure achieved complete remission of their diabetic symptoms, while only 7% of those in the gastric banding group normalized blood sugar levels. Five of the 19 patients who had sleeve gastrectomy (26%) achieved diabetic remission.
“It's clear that weight loss surgery, particularly gastric bypass, has a significant beneficial effect on glucose control,” said Dr Carel le Roux, from the Department of Medicine, who led the study.
The Roux-en-Y Gastric Bypass (RYGB), a procedure that includes the creation of a small gastric pouch and the bypass of the upper portion of the small intestine, is thought to affect glucose levels even prior to weight loss because it appears to regulate several body systems, including certain hormones that play a role in the metabolism of blood sugar almost immediately.
Although the sleeve gastrectomy and gastric banding also control portion sizes, resulting in a reduction of caloric intake, neither surgery includes the bypassing of the duodenum, a key factor in controlling blood sugar levels.
A separate study performed at the University of Gothenburg finds that bariatric surgery also achieves a reduction in risk for cardiovascular events such as heart attack and stroke. A team of researchers led by Lars Sjöström, MD PhD, a professor of internal medicine, studied over 4,000 very obese men and women for an average of 15 years. About half of the participants had one of three bariatric surgery procedures – vertical banded gastroplasty (a procedure not performed as much today in the US), gastric banding and gastric bypass.
The bariatric surgery patients were more likely to have lost weight than those who chose other methods, such as diet and exercise, but the amount of weight loss was not linked to a positive cardiovascular outcome. Those having WLS had only lost an average of 16% of their initial body weight, but were 33% less likely to have a heart attack or stroke during the follow-up period. They were also 53% less likely to die from a cardiovascular event should one occur.
"The benefit is similar at [both] smaller and larger subsequent weight losses," says Dr. Sjöström,
Why the difference? "Not everybody who has obesity has the same health risk," notes Edward H. Livingston, M.D., the chairman of gastrointestinal surgery at the University of Texas Southwestern Medical Center, in Dallas, who wrote an editorial accompanying the study. Although all participants were obese in this particular study, for example, none had been diagnosed with diabetes, which raises the risk of heart disease.
Another reason could be shear willpower. "People who understand bariatric surgery are individuals who are more motivated to address their health issues," he says. "The people who didn't pursue bariatric surgery are probably less likely to take care of themselves, or willing to take care of themselves, so the two groups of people are fundamentally different. I think it's that difference that accounts for the better outcome."
About 200,000 Americans undergo bariatric surgical procedures each year. In order to qualify for WLS, candidates should have a BMI of 40 or greater without additional co-morbid conditions, or a BMI of 35 or more when diabetes, heart disease or other condition is present. Last year, the U.S. Food and Drug Administration lowered the requirements for gastric banding to patients with a BMI between 30 and 40 who have at least one complicating disease.
DJ Pournaras et al. 'Effect of the definition of type II diabetes remission in the evaluation of bariatric surgery for metabolic disorders.' British Journal of Surgery, Volume 99, Issue 1, pages 100-103, January 2012
Sjöström L, et al "Bariatric surgery and long-term cardiovascular events" JAMA 2012; 307: 56-65.
Livingston EH "Inadequacy of BMI as an indicator for bariatric surgery" JAMA 2012; 307 88-89