Gastric bypass surgery is great for curing type 2 diabetes. It works for up to 80% of patients. Now scientists are beginning to figure out why. And weight loss may be the least of it. It turns out that bypass surgery dramatically reduces the amino acids circulating in the blood, in particular, a type called branched-chain amino acids, which make up 40% of these nutrients in our diet. That's from a study published today in Science Translational Medicine. Somehow this drop in amino acids (the building blocks of proteins) improves the body's response to insulin. That's the main problem in type 2 diabetes, a lack of insulin sensitivity. Or maybe whatever produces the fall in amino acids also makes cells more sensitive to insulin. However it works, the remarkable effect is that it normalizes blood sugar, correcting the diabetes.