Nearly 60 percent of dogs in the United Kingdom are overweight or obese, according to a recent study from the University of Glasgow. Using slightly different standards, researchers in the United States have found excess poundage in more than 45 percent of dogs and 58 percent of cats. How do they know when a pet is overweight?
By taking a good look and feeling for bones. The researchers assigned each animal a "Body Condition Score" of 1 to 7, according to a relatively new flowchart-based system (PDF) designed for pet owners. To determine a dog's BCS, the tester begins by running her fingertips gently along its coat, and deciding whether she can "easily feel the ribcage." In successive steps, she might feel for the spine, shoulder blades, or the indentation of the waist. Veterinarians more often use a 5-point or 9-point scale based on similar tactile and visual assessments. In general, a dog of "ideal" weight will have ribs that are easily felt, but not necessarily seen. There should also be a well-defined waist when viewed from above and a tucked-up abdomen from the side. Although based primarily on physical appearance, these scoring systems are strongly correlated with more objective measures of body fat percentage, like dual energy X-ray absorptiometry. That said, the huge variability in size and body type among different dog breeds has made developing a gold standard for canine obesity elusive.
While the data are more limited, studies indicate that excess weight is associated with many of the same problems in animals as it is in humans. Dogs that score high on the BCS scales are at greater risk for developing osteoarthritis and other orthopedic problems, as well as canine diabetes. Pudgy pets are also at increased risk for respiratory problems and cardiovascular disease, as well as reproductive disorders, certain skin conditions, and a number of cancers. Older fat cats are especially prone to kidney failure.
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Explainer thanks Ernie Ward, President of the Association for Pet Obesity Prevention and author of Chow Hounds: Why Our Dogs Are Getting Fatter—A Vet's Plan To Save Their Lives.