- People who undergo surgery lose 16% of initial body weight on average
- Amount of weight loss not associated with risk of heart attack, stroke, or death
- Health benefits associated with post-surgery weight loss vary
Obese people who decide to undergo stomach surgery to speed weight loss may lower their risk of having -- and dying from -- a heart attack or stroke, according to new research.
Swedish researchers followed 4,047 very obese men and women for an average of 15 years. Roughly half of the participants opted to have weight-loss surgery (also known as bariatric surgery) at the beginning of the study, and those who did were 33% less likely than those who skipped surgery to have a heart attack or stroke. They were also 53% less likely to die from one.
After 15 years, the people who underwent surgery had lost 16% of their initial body weight, on average, while those who didn't have surgery maintained roughly the same weight.
Surprisingly, though, the amount of weight loss among the surgery patients was not associated with the risk of heart attack, stroke, or death.
"The benefit is similar at [both] smaller and larger subsequent weight losses," says lead author Lars Sjöström, M.D., Ph.D., a professor of internal medicine at the University of Gothenburg.
The findings were published this week in the Journal of the American Medical Association.
The study, though relatively large, may not have been quite big enough to detect subtle relationships between weight loss and heart risk. (Only 199 participants in the surgery group, or 10%, had a heart attack or stroke, and just 28 died from one.) But it also could be that the health benefits associated with post-surgery weight loss vary from person to person.
"Not everybody who has obesity has the same health risk," says 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. "A lot of people are obese, but that obesity doesn't affect them that much."
For instance, although none of the study participants had diabetes, people with higher pre-surgery levels of the hormone insulin had a lower long-term risk of heart attacks and strokes than people with lower insulin levels who also had surgery. High insulin levels may therefore be important to consider when identifying candidates for bariatric surgery, Sjöström says.
Livingston says surgery may be especially beneficial for people who have diabetes. On the other hand, he says, obese patients with high blood pressure (hypertension) may see a relatively small reduction in long-term heart risk because hypertension is largely hereditary and is less likely to be affected by weight-loss surgery.
Mitchell Roslin, M.D., chief of bariatric surgery at Lenox Hill Hospital, in New York City, says the new study is notable because it tracked heart attacks and strokes over a long period of time, not just reductions in heart-disease risk factors such as cholesterol or blood pressure.
Bariatric surgery is still a relatively new procedure, however, and little is known about how well or how poorly people do over decades, Livingston says.
"We really don't know [the] long-term benefits or risks."
Of the 2,010 study participants who had surgery, 68% chose vertical banded gastroplasty, 19% underwent banding, and 13% had gastric bypass. The first two procedures involve banding or stapling the stomach to reduce stomach capacity (and appetite). Bypass surgery, meanwhile, creates a detour of sorts in the digestive tract that affects how food is absorbed.
A major shortcoming of the study is that the researchers didn't randomly assign the participants to have surgery. Even though the authors took into account factors such as smoking and cholesterol levels, the patients who decided to go ahead with surgery may be different in key ways from those who decided against it, Livingston says.
"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."