Q: Please review management of obesity in dogs and cats.

A: Dr. Alexander James German at the 2007 American College of Veterinary Internal Medicine Forum in Seattle gave an excellent lecture on obesity management. Here are some relevant points:

Obesity is defined as an accumulation of excessive amounts of adipose tissue in the body, which predisposes to a variety of diseases, including diabetes mellitus, osteoarthritis and cardio-respiratory diseases.

Causes of obesity

Obesity can be caused by a number of diseases, including endocrinopathies (e.g., hypothyroidism and hyperadreno-corticism in dogs) and drugs (e.g., polyphagia caused by glucocorticoids and anticonvulsant drugs), although the main reason for development of obesity is an imbalance in the energy-balance equation.

In this respect, either excessive dietary intake or inadequate energy use can lead to a state of positive energy balance, leading to increased white adipose tissue deposition. Numerous factors may influence the relative ease with which weight is gained, including genetics, age, neuter status, amount of physical activity and caloric content of the diet.

Treatment options

For dogs and cats, it is not considered ethically justifiable to manage obesity through surgical means.

However, pharmaceuticals have recently become available for treatment of obesity in dogs. In particular, releasing microsomal triglyceride transfer protein inhibitors that block the assembly and release of lipoprotein particles into the bloodstream are becoming available.

Such therapies may prove to be a useful addition to therapeutic options in the near future, although it should be stressed that, for any therapy (pharmaceutical, dietary, etc.) to have long-term success, it is essential to modify owner and animal behavior.

Unless steps are taken to change feeding habits and exercise patterns, weight regain will occur. This rebound effect is a well-known phenomenon of any weight-loss program.

To achieve long-term success, weight loss is only the start, rather than the end, of therapy. Conventional options for weight management include dietary therapy and behavioral modifications. Such strategies are likely to remain for dogs and, given that no pharmaceutical agents have yet been approved for cats, this approach will remain the mainstay of therapy in this species.

Dietary management

Weight reduction always should be tailored tothe individual dog or cat. Although complete starvation leads to rapid (about 7 percent per week) weight loss, it has the disadvantages of causing excessive protein (and thus lean-body mass) loss and requiring hospitalization to monitor.

Therefore, it is preferable to use purpose-formulated diets. Most formulated rations are restricted in fat and calories, while supplemented in protein and micronutrients. Protein supplementation is important because, although weight loss is not more rapid, the amount of lean tissue lost is minimized.

Supplementation of micronutrients ensures that deficiency states do not arise. Other diet components employed in weight management include L-carnitine supplementation (to maintain lean mass), conjugated linoleic acid and use of high-fiber diets (to provide satiety).

L-carnitine is an amino acid that is synthesized de novo, from lysine and methionine, in the presence of ascorbate. In a double-blind, placebo-controlled study, orally administered L-carnitine in a moist weight-loss diet for cats led to more rapid weight loss than placebo.

Dietary supplementation of L-carnitine improves nitrogen retention and body composition in favor of increased lean mass and decreased fat mass. Incorporation of L-carnitine at a level of 50 to 300 parts per million in weight-reduction diets has been shown to maintain lean tissue during weight loss.

Possible mechanisms for this protective effect on lean tissue include enhancing fatty-acid oxidation and energy availability for protein synthesis during times of need.

Conjugated linoleic acid (CLA) is a family of fatty-acid isomers derived from linoleic acid. Studies in experimental animals have suggested an anti-adipogenic effect; the mechanism of action is not known, but possibilities include inhibition of stearoyl-CoA desaturase activity that limits synthesis of monounsaturated fatty acids for triglyceride synthesis, and suppression of elongation and desaturation of fatty acids into long-chain fatty acids.