I see from a cursory Google that taking Byetta is used to help diabetics with blood sugar control who can't manager stability with the more usual drugs, it has the side effect that users often lose weight. So I presume your question is how heavy to people have to be before they're recommended Byetta? There doesn't seem to be any obvious answer so I'd say this is probably a question for your doctor or diabetic practitioner. You could try calling NHS Direct and asking them.
