Updated January 2010
The Centers for Disease Control and Prevention reports that obesity has increased dramatically in the United States during the past 20 years. While the CDC data describe the human population, other studies indicate that a substantial proportion of American pets also have become obese. Obesity has been reported to be the most common nutritional disorder in dogs, with an estimated prevalence of approximately 25%.
As obesity in dogs becomes more commonly encountered in practice, veterinarians are increasingly challenged to apply the most effective methods available for identification, treatment, and prevention. Articles in this collection have been selected on the basis of their relevance to clinical assessment and management of obesity in dogs and its health consequences.
In "Benefits of diet restriction" the effects of caloric restriction on lameness, chronic disease, and longevity are examined. A study from April of 2000, "Effect of weight reduction on clinical signs of lameness in dogs with hip osteoarthritis," opens this section with the finding that weight loss alone may improve clinical signs of lameness in overweight dogs. The remaining articles in this section include outcomes from a 14-year study of a group of Labrador Retrievers in which researchers tracked the effects of diet restriction from the time the dogs were 8 weeks old throughout the span of their lives. Half of the dogs received a diet sufficient to maintain normal body weight, while the remainder were fed 25% less. Multiple-joint arthritis occurred in just 10% of the diet-restricted group, compared with 77% of the control group, with hip joint osteoarthritis occurring in 50% of diet-restricted dogs, compared with 83% of control dogs. Additionally, the diet-restricted group had a mean lifespan nearly 2 years longer than the control group, as well as delayed onset of chronic diseases.
The "Obesity and health" section includes a study that found obesity to be a cause of expiratory airway dysfunction in dogs; a study that found early-age gonadectomy lowers incidence of obesity in both sexes, although it may cause urinary incontinence in female dogs; a study that found the relationship between obesity and cancer to appear to be incongruous, with obesity prevalence differing on the basis of cancer type as well as other factors; and a commentary offering insight into the role feeding plays in the mental health of animals. Also included are two articles that provide evidence of failure to recognize obesity — by pet owners and by veterinarians — as a health issue. The second of these articles includes data from more than 30,000 dogs examined at veterinary clinics across the United States. In that study, veterinarians reported obesity as a disease condition in only about half of all dogs with an obese body condition score.
Body condition scoring can be useful in recognizing obesity as a health condition, as discussed in the section "Considerations for treatment and prevention." In the first article, "Use of body condition scores in clinical assessment of the provision of optimal nutrition," the author emphasizes the importance of tying obese body condition scores to a diagnosis of obesity and to a specific health plan. Additional articles include findings that education of clients about nutritional methods to achieve greater weight loss in pets may be unrewarding, while inclusion of intense physical therapy in weight loss programs for obese dogs may improve signs of lameness to a greater degree than can be achieved through weight loss alone. The use of pedometers in canine obesity programs is also discussed, as are opportunities for companion animal veterinarians to have an impact on obesity in humans through their interactions with clients and the public.
"The role of nutrition" section begins with an article in which the authors explore methods for determining energy requirements in dogs through the use of body surface area and metabolic rate. An alternative view of fats in the diets of dogs is discussed by the authors of the next article, in which they point out that "good fats" and "bad fats" as recognized in human diets behave differently in dogs and, therefore, are more appropriately described as functional and facilitative fats. Lipid metabolism and its effect on weight management are discussed in "Dietary management of obesity in companion animals via alteration of lipid metabolism." The authors of two companion articles explore the applicability of evidence-based medicine to the management of obese pets, specifically examining the weight of evidence in support of nutraceuticals, dietary supplements, therapeutic foods, owner education, exercise, and drugs in obese pets.
In "Evaluation of calorie density and feeding directions for commercially available diets designed for weight loss in dogs and cats," the authors present findings from their study of 93 weight-management diets for cats and dogs, concluding in part that many pets would likely gain weight if fed as directed by the pet food manufacturer. And finally, to aid in discussions with clients who prefer home-made meals for their pets, the nutritional adequacy of home-made versus commercial diets is discussed in "Nutritional adequacy of diets formulated for companion animals."
The final section, "Biomarkers of obesity," presents evidence that plasma leptin concentration correlates strongly with body fat content, may be simple and practical to measure with an ELISA, and can be useful in the management of obesity in dogs.
These are just a few highlights of the clinical information to be found in the "Obesity in dogs" collection. We hope you will find it useful as you address obesity and its health consequences in your practice.