I dont get it, why would u switch if hes not old enough. They 're dogs. There suppose to be active and playful. If there not its because there too old like 11 - 13 or the owner has made them lazy. 7 years it not really old unless u own like a great dane. Why put yourself through all that work and money to switch foods. Also takes time for the dog to get used to new food. Meantime they could get bad diahrea. Anyways what im trying to say is, food shouldnt be the way to go. Excersize him more often. Food only plays a big factor when hes a puppy like mine. But still i work him hard. And he loves it. Always eager to run. Hes solid, cept for his belly (its so cute). If your dog just chooses to be lazy and lay around all day, its the owners fault. If you like the fact hes lazy, your cutting out good time in his life. If you want his be active, Im not saying he could be like a puppy, but i have seen some beautiful rotties and pitties and at 8 and older that play like puppies. Try to change his way of life. Bring him to parks alot more and long daily walks.