Same metabolic benefits from major weight loss – whether through diet or gastric bypass surgery

For severely obese people, it is weight loss alone that leads to improvements such as diabetes remission.

Gastric bypass surgery is the most effective therapy for treating or reversing type 2 diabetes in severely obese patients. Many go into remission from diabetes after surgery and no longer need diabetes medication. This observation has led to the theory that gastric bypass surgery has unique and independent effects of weight loss in the treatment of diabetes, but it has remained a long-standing question in the field. Now, new research from Washington University St. Louis School of Medicine indicates that losing weight after surgery, rather than the surgery itself, leads to metabolic improvements, such as remission from diabetes.

The researchers studied severely obese diabetes patients who underwent gastric bypass surgery and subsequently lost 18% of their body weight. In a patient who weighs 250 pounds, for example, that would be 45 pounds. The investigators compared these patients with others who were also severely obese and diabetic, but who 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 action of insulin in the liver, muscles, and fatty tissue, and a reduction in the need for insulin and other diabetes. drugs. Since the group that lost weight on diet alone did as well as the surgery group, the researchers concluded that the improvements were due solely to weight loss, rather than physiological changes resulting from the surgery itself.

The study is published on August 20 in The New England Journal of Medicine.

“It has been presumed that gastric bypass surgery has therapeutic and metabolic effects that result in better blood sugar control and even remission of diabetes beyond the expected effects of weight loss alone,” said the principal investigator Samuel Klein, MD, director of the Center for Human at the University of Washington. Nutrition. “But we found that gastric bypass surgery improves metabolic function by causing weight loss. There was no difference in the reduction in diabetes medication or in the rate of diabetes remission between patients who had surgery and those who lost equivalent amounts of weight through diet alone.

More than 40% of adult Americans are obese and nearly one in 10 is severely obese. Each year, more than 250,000 people in the United States undergo weight loss surgery to help them lose weight. The gold standard procedure, called Roux-en-Y gastric bypass, was the most successful operation in terms of total weight loss and long-term maintenance.

In this procedure, laparoscopic surgeons use a portion of a patient’s stomach the size of a soccer ball to create a pocket the size of a ping-pong ball that is connected directly to the small intestine, bypassing much of the upper part of the small intestine. In this study, gastric bypass procedures were performed by bariatric surgeons, J. Chris Eagon, MD, associate professor of surgery, and Shaina R. Eckhouse, MD, assistant professor of surgery.

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

Over a 24-hour period, the researchers used sophisticated in-hospital techniques to measure the study subjects’ metabolic responses to meals. They measured insulin sensitivity in the liver, fatty tissue, and muscle tissue. They also analyzed the response of insulin-secreting beta cells in the pancreas and blood. acid concentrations, all of which contribute to the development of type 2 diabetes.

“It has been suggested that the weight loss induced by gastric bypass surgery is different from the weight loss induced by a low calorie diet, based on the fact that certain factors, such as increased bile acid concentrations , decreased concentrations of branched-chain amino acids and alterations in the gut microbiome – are different in operated patients and may be responsible for the unique therapeutic effects of gastric bypass surgery, ”Klein said. “We found that all of these factors were, in fact, different after weight loss in operated patients compared to patients who lost weight only through diet. However, these changes were not associated with any physiologically or clinically important metabolic benefit.

According to Klein, also William H. Danforth Professor of Medicine and Nutritional Science and Head of Geriatrics and Nutritional Science, weight loss is the reason for improved metabolic function and health. reversal of diabetes. Weight loss through dieting produces the same beneficial metabolic effects as weight loss after surgery.

In a supporting journal editorial about the article, researchers at Tufts University, Harvard University, Massachusetts General Hospital and the University of Maine write that the study “sends a message simple and important for clinicians and patients – reducing the volume of fatty tissue, by any means, will improve blood sugar control in people with type 2 diabetes. “

“However, losing 18% of body weight with diet therapy alone is extremely difficult and unrealistic for most obese people,” Klein explained. “In contrast, gastric bypass surgery results in marked and sustained long-term weight loss, making it an effective treatment for people with diabetes.”

Klein’s study focused on the effects of gastric bypass surgery on metabolic function and did not examine other medical complications associated with obesity.

“Our study does not exclude the possibility that gastric bypass surgery has unique effects independent of weight loss on important clinical outcomes such as arthritis, lung function or cancer risk, which did not been evaluated. But when it comes to metabolic health, gastric bypass surgery is effective because it results in weight loss, ”he said.

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Reference: “Effect of diet versus gastric bypass on metabolic function in diabetes” by Yoshino M, Kayser BD, Yoshino J, Stein RI, Reeds D, Eagon C, Eckhouse SR, Watrous JD, Jain M, Knight R, Schechtman K, Patterson BW, Klein S, Aug 20, 2020, The New England Journal of Medicine.
DOI: 10.1056 / NEJMoa2003697

This work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases, the National Heart, Lung and Blood Institute, and the Office of the Director of the National Institutes of Health (NIH). Grant numbers R01 DK101578, P30 DK56341, U24 DK097153, T32 DK007296, T32 HL120257, K01 DK116917, P30 DK063491, S10 OD020025, R01 ES027595 and P42 ES010337. Additional support was provided by the Barnes Jewish Hospital Foundation and the Pershing Square Foundation.

The 1,500 physicians in the Washington University School of Medicine are also on the medical staff at Barnes-Jewish and St. Louis Children’s Hospitals. The School of Medicine is a leader in medical research, education, and patient care, ranking among the top 10 medical schools nationwide by US News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children’s Hospitals, the School of Medicine is linked to BJC HealthCare.