I had a really hard time as well getting Morgana to put on weight.... No matter how many crickets I fed her or how long I left her salad in her habitat she stayed thin.
I called a vet friend that works in a zoo in Columbus Ohio, (and is also a beardi/iguana/gecko lover and owner for 15+ years) and asked her what she could tell me to do about getting Morgana to gain a little more weight....
She gave me a simple website and told me to read :
http://www.phoenixworm.com/servlet/StoreFrontThat is the best thing I ever did. Morgana has now put on weight, vet check ++ on her health, she is shedding like she is supposed to, the whole nine yards!!
They have an awesome first time buyer deal, which is what I started off doing, now I buy the 1000 mediums. Morgana paces the front glass as soon as she sees the black container they come in, just waiting for her first bite! I have posted pics of Morgana when I first got her on this site in the photo area ....you can see how small and thin she was! I will upload some new ones tomm.... wait till you see how she has changed!