An extraordinary thing happens to some patients with type 2 diabetes who undergo weight-loss surgery: Within days of the procedure, they improve their insulin production and need fewer or no diabetes medications. Although it’s well established that losing weight, especially around the waistline, improves pancreas function and insulin sensitivity, it generally takes 6 months to a year after bariatric surgery before a patient sheds a substantial number of pounds.

Bruce M. Wolfe, MD, professor of surgery at Oregon Health and Science University School of Medicine, recalled one “remarkable” case in which a patient who required 400 daily units of insulin prior to gastric bypass surgery needed none on the day she was discharged from the hospital.