Do you leave food out for him? Or will he eat dry food? I leave it out all the time for Suzi, and she goes to it whenever she is hungry, AND I also feed her canned puppy food, and a bit of white chicken meat...
Suzi is on the lean side too. She goes to the vet today, a month ago she was 3.5 lbs. I think she has gained some weight now. Maybe 4 or 4.5 lbs.