OBESITY: ARE WE DOING ENOUGH?

By Anthony Carr, DVM, Dipl. ACVIM

editor's note: The below article was written for veterinary practitioners and was first published in Veterinary Practice News, April 2004.

Although obesity prevalence in dogs and cats vary from region to region and study to study, there is little doubt that obesity is the most common nutritional problem seen in small animal practice. A variety of medical conditions have been linked to obesity including diabetes, skeletal problems, hepatic lipidosis (fatty liver disease) and high blood pressure.

In addition, obesity tends to be a disease that becomes more prevalent with age. Aged pets are also more likely to suffer from concurrent medical problems such as endocrine disease (hypothyroidism, hyperadrenocorticism), cardiac disease (valve endocardiosis) and renal disease, which may be influenced by obesity.

Because obesity has such significant effects on the health of pets, it is vital for veterinarians and owners to be cognizant that being overweight is not just a matter of appearance. It is a significant health issue that needs to be addressed.

Obesity-Related Diseases

Diabetes: The link between obesity and diabetes mellitus in cats and humans has been convincingly demonstrated. Many cats have Type II diabetes or noninsulin dependent diabetes. Their pancreas still produces insulin, just not enough to maintain normal blood glucose. This is often a result of insulin resistance induced by obesity. The exact mechanisms underlying insulin resistance have not been elucidated, though resistin and leptin play a role. In overweight diabetic cats, weight reduction is an important management tool and, in some cases, can resolve the diabetic state.

Orthopedic problems: Whether obesity causes osteoarthritis is uncertain. It certainly is clear that increased body weight changes how osteoarthritis is manifested. Overweight dogs are much more likely to show clinical signs such as lameness than normal-weight dogs. Weight loss in dogs with hip dysplasia significantly improved their clinical condition.*1 Obese animals are much less exercise tolerant. This means that they have a harder time maintaining muscle mass. A prolonged recovery period is to be expected in overweight animals after surgery or trauma.

Hepatic lipidosis (Fatty liver disease): Hepatic lipidosis is a complex disorder. Many diseases have been associated with the development of fatty liver in cats. One consistent finding is that it predominantly affects overweight cats that lose weight rapidly. This will not occur in all obese cats; however, when it does develop it is a difficult disease to treat and a certain number of affected cats will die.

High blood pressure: Obesity is known to be associated with significant increases in blood pressure in humans and dogs.*2 The genesis of blood pressure increases in obesity is incompletely understood with different mechanisms responsible for short-term and long-term effects.

It appears that the interaction of hyperinsulinemia, insulin resistance, hypertriglyceridemia, volume expansion, increased cardiac output, abnormal kidney function, and increased sympathetic activity all play a role in elevating blood pressure in obese dogs and humans.*3

Diet Restriction and Lifespan

When clients are apprised of the fact that their pets are overweight and that this is something that could significantly decrease the pets' quality of life, it has been my experience that clients are almost always willing to do what it takes to achieve weight loss. I also have been struck by the fact that almost all clients are very happy to have instituted a weight loss program because their four-legged family member became much more active and playful.

References
1. Impellizeri JA, et al. Effect of weight reduction on clinical signs of lameness in dogs with hip osteoarthritis. JAVMA 2000;216:1089-1091.
2. Bodey AR, Michell AR. Epidemiological study of blood pressure in domestic dogs. J Small Anim Pract, 1996;37:116-125.
3. Joles JA. Obesity in dogs: effects on renal function, blood pressure and renal disease. Vet Quart 1998;20:117-120

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Anthony Carr, DVM, Dipl. ACVIM is an associate professor at the Western College of Veterinary Medicine in Saskatoon, Saskatchewan, Canada. He completed his veterinary education at the Ludwig Maximilians University, Munich, Germany. He then went on to complete a residency program in internal medicine at the University of Wisconsin-Madison. After completing the residency program, Dr. Carr worked as a clinical instructor at Wisconsin's Veterinary Teaching Hospital and as staff internist for the Emergency Clinic for Animals in Madison, Wisconsin. Dr. Carr is widely published in the United States and Germany and is an editorial board member of Veterinary Forum magazine.