Major weight loss from surgery or diet has same metabolic benefits

Aug. 20, 2020

Gastric bypass surgery is the most effective therapy to treat or reverse type 2 diabetes in severely obese patients. However, new research indicates that weight loss after surgery, rather than the surgery itself, drives metabolic improvements, such as the remission of diabetes, according to the Washington University School of Medicine in St Louis (WUSTL).

Many achieve remission of diabetes following surgery and no longer require diabetes medications. This observation has led to the theory that gastric bypass surgery has unique, weight loss-independent effects in treating diabetes, but this has remained a longstanding question in the field

The WUSTL researchers studied severely obese patients with diabetes who had gastric bypass surgery and then lost 18 percent of their body weight. In a patient who weighs 250 pounds, for example, that would be 45 pounds. The investigators 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.

More than 40 percent 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 this study, the gastric bypass procedures were performed by bariatric surgeons, J. Chris Eagon, MD, an associate professor of surgery, and Shaina R. Eckhouse, MD, an assistant professor of surgery.

Klein’s team compared 11 gastric bypass surgery patients who had diabetes with 11 others who had diabetes and achieved equivalent weight loss with diet alone. The average age of patients in the diet group was about 55, while the average in the surgery group was 49. Those in the surgery group lost an average of 51 pounds, while those in the diet group lost an average of 48 pounds. All study patients maintained that weight loss for several weeks before follow-up studies were performed.

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