[header] How to know if your dog needs a diet change [title] Notice if your dog appears lethargic or tired. [step] Maybe you notice your dog appears more tired or worn out than usual. They may not be as excited about going for walks or seem less enthusiastic about playing with you than they usually are. 
You may also notice your dog spends a lot of time sleeping or lying down. These may all be behavioral signs that your dog may be due for a change in diet.