Hi Carol.
You may want to ask your vet to prescribe a special diet food for Misty. My vet recently prescribed a special food for my cat Romeo who has diabetes, but there are also weight maintenance benefits to the food. One brand is Hills, and they make an r/d formula that aides in weight reduction. I had two of my cats on the Science Diet Maintenance formula, but the vet said that would not help them lose weight, and would only help them stay at the current weight. Romeo use to weigh about 17 pounds, but is now at about 12 pounds because of the diabetes. As you know from your vet, that is a huge weight lose in a one year period. I think proper weight maintenance is crucial in cats. Hope this helps. Good Luck