oh PLEASE PLEASE PLEASE stop feeding him Iams... not a good food.... go here
http://www.dogfoodanalysis.com/dog_food_reviews/
and look at the 4,5 and 6 star foods. That is what he should be eating if you are going to home cook. When you start... he will probably have diarrhea,... which is normal.. his body is cleaning out the crappy food and kinda just cleansing itself.