insulin isn't a good idea unless you have to use it. it can cause huge fat gains if your diet isn't perfect AND YOU COULD DIE IF USED INCORRECTLY! and its not an "oh you could die if you take too much over a long period of time where you'd have plenty of warning signs to get medical attention" - its more like you go hypoglycemic and bam you go unconscious within minutes and die unless someone knows you use insulin or thinks you diabetic and forces sugar into your system in a damn quick fashion.
it can be used smartly but you better have a damn good understanding of how it work and how long it works. unless you have no other choice (meaning a diabetic or competing pro), you shouldn't use insulin. its just stupid.