I have CFRD and problems gaining weight. As far as diet, my diabetic doctor told me that because with CF weight is such an issue that they were not going to restrict or change my diet, and I control the numbers by carb counting. I have a ratio of 1 unit of insulin to 25 grams of carbs, so when I eat anything I count em up and inject the amount of insulin needed.
For me, personally, getting the sugars under control didn't help my weight gain.
I know there are a few medications that can be taken by mouth before insulin becomes a necessity. I don't really know much about those. My doctor mentioned them and then realized I couldn't take any because I have liver issues and the risk outweighed the benefit.
If insulin is necessary, I recommend going with a pump. I started with insulin pens and moved to the pump. It's much easier and much less sticking considering that I'm a big snacker. <img src="i/expressions/face-icon-small-smile.gif" border="0"> It's definitely another thing to deal with, but it becomes habit and part of the routine fast enough. Also - there are really great phone apps that have carb amounts for popular foods from restaurants as well as just about everything else to help with carb counting. Just an FYI. <img src="i/expressions/face-icon-small-smile.gif" border="0">