I have a small dog who was severly over weight because my husband is a softy! and would give her a hefty seving of whatever we eat no matter what she already had. after a visit ti the vet for coughing and finding out that she was retaining lots of water due to the salt in our food, she has heart failure (left side deteriation) the extra weight is hard on her tiny legs and was squeezing her organs. She'll eat the expensive containers of dog food but no dry AND she was hungry ALL the time ( I know the feeling!) I boil the meat, mostly calf liver and mush it up so it's mixed throughout, and some barley and a bag of mixed veggies. I give her a cup in the morning with her meds and a cup when we eat supper, I put down about 1/2 cup of a good dry food during the day, if she's really hungry she'll eat it. it's not cheaper than can food but I do feel that it's better for them. We have a large old unhealthy lab too so I cook "dog soup" about twice a week!
good luck