Gymnema (Gymnema sylvestre) is a plant native to India and Africa with a history of use in Ayurvedic medicine. It has little evidence of health benefits.
Gymnema contains chemicals that reduce how much sugar the stomach absorbs. It might also increase the amount of insulin in the body and increase the growth of cells in the pancreas, which is where the body makes insulin.
People use gymnema for diabetes, obesity, and many other conditions, but there is no good scientific evidence to support these uses.