| I do believe that insulin is anabolic and anticatabolic, meaning it can help maintain mass, however, I am too lazy at the moment to try and track down anything confirming this on pubmed or any respectable website.
I personally used to inject primarily in my arms and yes I do feel that I developed more muscle in my arms relative to the other body parts (at the time I was lifting like crazy and playing rugby). My brother actually asked me at some point if I was using steroids.
Incidentally, an endocrinologist I was seeing some years ago mentioned that diabetics that inject into their arms tend to develop "popeye arms", meaning they tended to be oversized relative to the rest of their build.
I wouldn't start injecting in your abdomen thinking this is going to net you a great set of abs. Really that is going to come down to working out hard and following a strict diet. Abs are one of those muscles that can be well developed in an individual but may never be noticable do to the persons body fat percentage. Really if you want to show your abs, focus on your diet.
Remember that insulin, will also pack on fat. So really just get to the gym work out, and watch your diet.  | 
