If your dog's Cushing's is appropriately controlled on Vetoryl, then I would suggest testing her for hypothyroidism, which can also cause weight gain. If the thyroid testing is normal, then I would recommend talking to your veterianarian about a prescription reducing diet such as Royal Canin Restricted Calorie, Purina OM, or Hill's R/D. While on the reducing diet, she should be fed the precise measured amount recommended by your veterinarian, and be weighed every 2 weeks. She should lose 1-2% of her body weight weekly to the desired weight, which will be determined by your veterinarian. Once her breathing gets better, then you can also start exercising her more to increase weight loss. There is also a weight loss "pill" that you can talk to your veterinarian about that, in combination with diet and exercise, can help obese dogs lose weight.
Kimberly Coyner, DVM
I am uncertain of your question. What is the medication name, and when was the last time that bloodwork was performed on your dog to monitor control of the Cushing's?
Kimberly Coyner, DVM