Been there, done that.
When our oldest was 2 she was diagnosed with food allergies, wheat, egg, milk, tomatoes, green beans, peas and carrots. Anyway we got rid of everything in the house that contained any of those ingredients, and every member of our household lost weight immediately. By the time she got to be 6-7 she had outgrown every one of them except the egg allergy. So now we have all those things back in the house and we've all gained weight. So when I started my heavy duty diet in Jan 2010, I went back to many of the foods we used to eat when she was allergic to everything.