Gastric bypass surgery is the most effective therapy to treat or reverse type 2 diabetes in severely obese patients.
Many achieve remission of diabetes following surgery and no longer require diabetes medications.
This finding has led to the theory that gastric bypass surgery has unique, weight loss-independent effects in treating diabetes, but this has remained a long-standing question in the field.
In a new study, researchers found that weight loss after surgery, rather than the surgery itself, drives metabolic improvements, such as the remission of diabetes.
The research was conducted by a team from Washington University School of Medicine in St. Louis.
More than 40% of adult Americans are obese, and close to one in 10 is severely obese. Each year more than 250,000 people in the U.S. undergo bariatric surgery to help them lose weight.
The gold standard procedure, called Roux-en-Y gastric bypass, has been the most successful operation in terms of total weight loss and long-term maintenance.
In this procedure, surgeons working laparoscopically use part of a patient’s football-size stomach to create a pouch the size of a ping pong ball that is connected directly to the small intestine, bypassing much of the upper portion of the small intestine.
In the current study, the team tested severely obese patients with diabetes who had gastric bypass surgery and then lost 18% of their body weight. In a patient who weighs 250 pounds, for example, that would be 45 pounds.
The team compared those patients with others who also were severely obese with diabetes but had lost the same percentage of body weight through diet alone.
After reaching their weight-loss goals, members of both groups experienced similar improvements in metabolism—such as lower blood sugar levels throughout the day, better insulin action in the liver, muscle, and fat tissue, and reductions in the need for insulin and other diabetes medications.
Since the group that lost weight through diet alone did just as well as the surgery group, the researchers concluded the improvements were due to weight loss alone, rather than to any physiological changes that resulted from the surgery itself.
The study delivers a straightforward and important message for both clinicians and patients—reducing adipose tissue volume, by whatever means, will improve blood glucose control in persons with type 2 diabetes.
However, losing 18% of body weight with diet therapy alone is extraordinarily difficult and unrealistic for most people with obesity, the team explained.
In contrast, gastric bypass surgery leads to marked and sustained long-term weight loss, which makes it a potent therapy for people with diabetes.
One author of the study is Samuel Klein, MD, director of Washington University’s Center for Human Nutrition.
The study is published in The New England Journal of Medicine.
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