A key goal for the nutritional management of heart disease is to maintain optimal body weight, because both weight loss and obesity can be harmful to your pet. Owners should watch their pets for loss of overall body weight and loss of muscle (cachexia describes muscle loss seen in animals with heart disease).
To assess your dog or cat's muscle condition, please see the following links the the World Small Animal Veterinary Associations Nutrition Toolkit site:
Many pets with heart failure will not eat as much, as frequently, or the same things as when they were healthy—this is called anorexia. This can be an important factor in the weight and muscle loss that occurs. Maintaining your pet's interest in food is a tricky, yet important, task but there are several tips to achieving this.
First, try giving more frequent, but smaller meals. Cats frequently are more interested when the food is warmed. Dogs are less predictable, but will usually prefer one temperature over another (try different temperatures—warmed, room temperature, cold or even frozen).
Another method to manage reduced or changed appetite in an animal with heart disease is to gradually replace their current food with a new one. For example, switch from a dry food to a canned food, change to a different brand, or have a qualified nutritionist formulate a balanced homemade diet. However, be sure to talk to your veterinarian about the diet that is most appropriate for your pet.
Finally, flavor enhancers such as cooked meat or fish (without any salt; avoid deli meats) for dogs and cats, or sweeteners (such as yogurt, maple syrup, applesauce or honey) for dogs may be added to the diet to promote eating. Fish oil may be given to help with cachexia, as is described on the Important Nutrients page.
As it is important to make sure animals are not too skinny, it is also necessary to make sure they are not too heavy. Owners often find that severely overweight dogs and cats with heart disease that successfully lose weight, appear to have less trouble breathing and are more comfortable. A special diet may be prescribed for your dog or cat to help treat the heart disease as well as to maintain their optimal body weight. Please see the diagrams below, which illustrate thin, heavy, and optimal weights for pets.