I worked with a trainer for a few years, bread was a good part of their diet. As well as chicken,horse,tripe,dry greyhound dog food,pasta,tuna,all sorts of veg... Everything basically, it all went in the pot.
Not a skinny dog in sight
You could try feeding satin balls? Here's a recipe for them-
http://www.dogforum.net/dog-frequently-asked-questions/5191-how-make-satin-balls-fat-balls.html