My Black Lab Lost Weight

My neighbours were feeding scraps while my dogs were outside. I was always wondering why my Dog on a literal schedule would go to the side of the house. I can say that my new puppy (Cane Corso) was getting treats without my permission. Anyways I put my senior 11.5 year old dog on a new dog food and in this video he is moving like 5 years ago although his muscle mass is lost.