Any weight gain in your pet should be taken seriously because getting heavier could signal or lead to more complicated problems like thyroid disease, diabetes, or osteoarthritis.
One pound on a pet can equal six to eight pounds on a human. Also, if a pet leads a sedentary life, it's hard to get extra weight off. The good news is that you are in control of this situation. Your pet can't open the cabinet and get out more food. So a change in diet—either feeding a therapeutic food designed to encourage weight loss, changing portion sizes, or eliminating snacks—should help.
If your pet is on a good diet and still not losing weight, it's a good idea to run blood work. Metabolic disorders such as thyroid disease can affect how a pet loses or gains weight. Your veterinarian will help guide you in keeping your pet's weight where it should be!