If things have been up and down and the BG readings have fluctuated greatly (as you say) for the past 5 years, I am surprised his Doc has not made any significant changes to his
insulin schedule and / or type of
insulin. DO not get me wrong, I am not crticizing his Endocrinologist. (although it may sound like it) Possibly he made changes and they just have not helped??
I am sure his appetite is much bigger than when he was a kid or even a pre-teen.