Yesterday my husband and I purchased an 8 month old male GSD pup we have named Cash, His owners were feeding him 5 cups of Hills Science Diet per day. From what they told me their vet told them to do that to keep him lean at this age. I have seen lean dogs and I have seen dogs that are skinny. Cash looks too thin to me. His ribs can easily be seen and he just looks too thin. His spine is easily felt and his hips are the same way. I don't want to get him to the point of being obese but I want him filled out a lot more than he is. I understand keeping a pup slim and lean to keep developing bones healthy and keeping joints strong but when is lean too lean? Valkyrie is lean but her ribs are not easily seen she has a nice tuck and looks really good. She is 6 1/2 months old will be 7 months on Saturday.