Although taken by injection, exenatide (Byetta) is not insulin. Byetta improves blood sugar control by mimicking the action of the hormone incretin. Among other things, Byetta allows insulin to work more effectively in the body.
In studies, Byetta not only improved blood sugar control but also led to weight loss. It's unclear exactly how Byetta causes weight loss, but one effect of the drug is that it delays the movement of food from the stomach into the small intestine. As a result, people taking Byetta may feel "full" faster and longer, so they eat less. The most common side effect of Byetta is mild to moderate nausea, which improves with time in most people. Rarely, Byetta may cause harmful inflammation of the pancreas (pancreatitis).
Byetta is designed for people who have diabetes and has not been studied as a weight-loss aid in people who have normal blood sugar. If you have diabetes and wonder if Byetta may be helpful, talk to your doctor.