We all hear about weight gain on insulin. Docs warn us about weight gain on insulin. And then, gasp!, they are surprised when some T1's gain weight on insulin. Shocked!
When I was in college I worked with the university pediatric endocrinology department where my project was some "at risk" T1 kids with poor control. I would generalize and say that the underweight T1's? Definitely sky high bg's all the time, largely because they're taking insulin irregularly at best. Ironic because the stereotype in the public and even the medical establishment is that being paunchy is the sign of a "bad diabetic".