Nearly 30 years ago, Pories and colleagues published a landmark case series provocatively titled 鈥淲ho Would Have Thought It? An Operation Proves to Be the Most Effective Therapy for Adult-Onset Diabetes Mellitus.鈥�¹ The operation was the gastric bypass for obesity. The excellent well-controlled study published in this issue of JAMA by Courcoulas and colleagues² provides the most robust evidence to date of the long-term efficacy of bariatric surgery for improving control of type 2 diabetes. Effective therapies are critically needed for this disease, which affects more than 14% of adults in the US, is associated with a high burden of both physical and mental health complications, and incurs annual direct medical costs of $306.6 billion.^3,4