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.
In most animals, obesity is the result of a simple imbalance between energy intake and energy expenditure.
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.
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.
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.
Currently, there are conflicting data on the benefit of CLA as an anti-obesity agent in humans and cats, with the most recent data suggesting lack of a significant effect. Therefore, more information is needed before it can be recommended.
A major hurdle to conventional weight-loss programs is the fact that energy restriction causes hunger, leading to increased begging and scavenging activity. This puts increased strain on the owner-animal bond, causing owner non-compliance or complete withdrawal from the program.
Therefore, developing strategies to improve satiety would greatly assist in case management. Many human studies show that absorption of macronutrients is lower following consumption of high-protein foods than after consumption of foods with a high carbohydrate or fat content.
The amino acids from the digestion of proteins are absorbed slowly, and the main path of their metabolism is gluconeogenesis.
Therefore, proteins are sources of glucose that induce little insulin secretion and delay the appearance of hypoglycemia (which contributes to the feeling of hunger).
The satiety effect of proteins is variable, because speed of digestion varies among different proteins, and different amino acids induce the secretion of insulin to varying degrees.
Dietary fiber may increase satiety, due to gastric distension which causes cholecystokinin release and a subsequent slowing of gastric emptying.
Under certain conditions in humans, dietary fiber has been shown to exert a satiety effect, although some studies have failed to detect significant reduction in appetite. There are similar discrepancies in dog studies with some, but not all, suggesting effects on satiety. Apparent inconsistencies are likely the result of differing investigative methods and of the dose and type of fiber used.
In recent studies in colony dogs, three different diets (HPHF, high protein [103g/1000Kcal] high fiber [60g/1000Kcal]; HP, high protein [104g/1000Kcal] moderate fiber [35g/1000Kcal]; HF, moderate protein [86g/1000Kcal] high fiber [87g/1000Kcal]), designed for weight loss were assessed for their satiety effect.
Voluntary food intake was measured in five sequential crossover studies. Palatability was assessed with taste tests.
Short-term (food offered for 15 minutes every hour for four hours) and medium-term (food offered three hours after the first meal) satiety was best for the HPHF diet.
Voluntary food intake at the second meal (fed three hours after a restricted meal of 25 percent of daily metabolic energy requirements) was significantly lower than the first meal for the HPHF diet, but not the HP or HF diets.
The HPHF and HP diets had equivalent palatability, and both were more palatable than the HF diet.
These studies suggest that diets supplemented in both protein and fiber have the greatest satiating effect, and may improve compliance with conventional weight-loss programs.
Increasing physical activity is a useful adjunct to dietary therapy during weight management. Studies in humans suggest that increasing activity promotes fat loss, while preserving lean tissue during weight loss. The exact program should be tailored to the individual, and take into account any medical concerns.
Suitable exercise strategies in dogs include lead walking, swimming, hydrotherapy and treadmills.
Exercise in cats can be encouraged by increasing play activity, using cat toys (e.g., fishing-rod toys), motorized units and feeding toys.
Cats can be encouraged to work for their food by moving the food bowl between rooms prior to feeding, or by the use of feeding toys. Activity monitors (accelerometers, pedometers) recently have been validated for dogs, and may help provide a more objective assessment of activity during weight-loss programs in the future.
In humans, diet and exercise are the main methods of achieving weight loss, but some patients require drugs to help maintain the loss.
Drugs used to aid in obesity management include intestinal lipase inhibitors (e.g., orlistat), drugs that inhibit reuptake of noradrenalin and serotonin (e.g., sibutramine) and cannabinoid-receptor antagonists (e.g., rimonabant).
In general, these have a modest beneficial effect; they increase weight loss at about 4-6 kg beyond what can be achieved by diet alone, they maintain weight loss at about 2-15 kg below baseline and they improve most cardiovascular risks in direct relation to weight loss.
However, a range of side effects are seen with all medications, and this can limit their overall benefit.
Recently, two drugs were approved to assist in the management of obesity in dogs. Both are microsomal triglyceride transfer protein inhibitors that block the assembly and release of lipoprotein particles into the bloodstream.
Dirlotapide can be used as sole therapy for obesity for up to 12 months. It acts partly by preventing lipid absorption and partly by reducing appetite. Its effect appears to be a local one in the gastrointestinal tract; a similar effect does not occur when the drug is administered intravenously.
The effect on satiety avoids the need for a dietary change and eliminates negative behaviors that can lead to poor compliance with a weight-loss regimen. The most common side-effect is vomiting, which can occur in up to 20 percent of dogs using the drug.
While on the drug, weight loss is highly successful. However, a predictable rebound occurs when the drug is discontinued.
Mitratapide is a drug recently approved to aid in weight loss. It has both local (gastrointestinal) and systemic effects. It is designed for short-term use in conjunction with dietary management and behavioral modification.
Monitoring weight loss
In addition to these strategies, it is essential to supervise closely the whole weight-reduction regimen. This is labor-intensive, requires some degree of expertise and training in owner counseling and often requires a dedicated member of staff.
Nevertheless, correct monitoring is the single most important component to the weight-loss strategy. A recent study demonstrated that weight loss is more successful if an organized approach is followed with regular weigh-in sessions.
It is essential to continue to monitor body weight after ideal weight has been achieved to ensure the weight that was lost is not regained.
As with humans, a rebound effect has been seen in about 50 percent of dogs after weight loss.
Dr. Hoskins is owner of Docu-Tech Services. He is a diplomate of the American College of Veterinary Internal Medicine with specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200 or e-mail: