A: It’s important to formulate a plan for your pet with a vet’s guidance. An easy way to kickstart your cat's diet is to feed it a specified serving of diet food that is 20 percent lower in calories than its previous, non-diet food. After a week of this, check your cat's weight. If it dropped more than 2 percent of its original weight, increase the food serving. If it dropped less than 2 percent, cut back a bit more. Cats that lose right around 2 percent can stay on the same feeding schedule. Continue to weigh your cat and adjust its food every week. Mix in interactive play, too. Follow this routine until your cat is down to its goal weight.