By Theresa A. Fuess, Ph.D.

As the proud and loving owner of one roly-poly ball of purring fur, I felt obliged to find out how obesity can affect a pet's health. After all, there is no societal pressure for my cat to be sinewy slim, and she is quite content with her physique. The process of slimming her down certainly poses a risk to her ambient happiness level. How does this compare to the risk to her health of being so round? I asked the advice of Dr. Jennifer J. Brinson, veterinarian and researcher on obesity in pets at the University of Illinois Veterinary Medicine Teaching Hospital in Urbana.

There may be diseases caused by obesity in dogs and cats but what we see more often are ordinary medical problems made worse by obesity, explains Dr. Brinson. For example, pets of any body condition can get diabetes, but the disease is more difficult to manage in obese pets because the additional body fat interferes with insulin effectiveness. Problems such as torn ligaments are more common in obese pets both because of their disproportionate size and because they often do not have the muscle tone to balance and support the extra weight. Arthritis is not caused by obesity but may be worsened by the extra load on the arthritic joints.

Just about every organ in the body may be affected by obesity, but most at risk are the musculoskeletal, cardiovascular, and respiratory systems. Obesity also compromises the effectiveness of a proper physical exam. Body fat can mask heart and lung sounds. The consistency and size of abdominal organs are difficult to feel through intervening fat, says Dr. Brinson. This may prevent the veterinarian from finding early indicators of disease and delay diagnosis until a disease has reached advanced stages.

What causes obesity in pets? There are diseases, such as hypothyroidism and Cushing's disease, that are associated with weight gain. There are also hormonal influences, genetic influences, and individual variation in metabolism and appetite, but unfortunately the most frequent cause of obesity in pets is owner indulgence of treats and/or oversized portions of pet food. Owners do not realize that they are killing pets with kindness, says Dr. Brinson.

Excess weight is easier to prevent than to lose. The more weight there is to carry around, the more inactive a pet becomes, the harder it is to exercise and reduce weight. Visits to your veterinarian for your pet's cycle of puppy or kitten shots should include weight monitoring. Then adjustments in diet and exercise can be made early and problems with obesity avoided.

If prevention is a missed opportunity, then the first step toward weight reduction and improved health is a visit with your veterinarian. Metabolic problems contributing to weight gain should be corrected before changing your pet's diet or routine. Your veterinarian will also know the ideal weight for your pet and can provide a healthful diet and exercise plan with well-defined goals and regular weight loss.

Pets are best exercised by playing with them. Take the dog for walks. Play fetch. Give the cat chase toys. If your cat follows you up and down stairs, then walk up and down stairs, tour the house, everyday; don't stop until the cat stops. If an owner is unwilling to exercise, then the pet will not get exercise.

Feeding a lower calorie diet or smaller portions of your pet's regular diet can reduce calories in a pet's diet. Your pet will tell you whether higher volume or concentrated calories are preferred. However, owners should realize that low-cal diets often have more fiber and may increase the quantity of feces produced. Dogs may not be able to hold it all day like they could with their lower fiber diet. Cats are finicky eaters and often refuse diet food. Owners of cats should be careful not to let their cat starve or lose weight too fast. Dr. Brinson emphasizes that a pet's health is the owner's responsibility. “Pets don't choose what or how much to eat. Owners dictate the animal's diet and how much they get. People food, table scraps, and fast-food take-out should not be options. There are dietary treats that are good for pets that will also satisfy the owner's need to indulge the pet.”

By Theresa A. Fuess, Ph.D., Information Specialist, University of Illinois College of Veterinary Medicine.