Obesity in dogs, Part 1: Exploring the causes and consequences of canine obesity - Veterinary Medicine
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Obesity in dogs, Part 1: Exploring the causes and consequences of canine obesity
This increasingly common condition decreases a dog's life span, increases its risk for various cancers, and causes orthopedic problems—just to name a few of the possible sequelae.


VETERINARY MEDICINE


PREVALENCE AND CAUSES

Obesity is one of the most important medical problems in dogs. Studies from throughout the world have estimated the prevalence of overweight or obese dogs to range between 22% and 40%.13-17 Cross-sectional data suggest one in three dogs seen by U.S. veterinarians is overweight.18

Breed predisposition

Recent data in various animal species provide new insight into the genetic basis of obesity.19-21 A significant breed predisposition to obesity has been shown in certain breeds including Cairn terriers, West Highland white terriers, Scottish terriers, Shetland sheepdogs, basset hounds, Cavalier King Charles spaniels, dachshunds, beagles, cocker spaniels, and Labrador retrievers.12,15,22-24 Conversely, certain breeds, particularly sight hounds, appear to be resistant to the development of obesity.24

Age

As an adult animal ages, lean body mass declines, resulting in a decrease in total daily energy needs.25 The loss of lean body mass is exacerbated if aging is accompanied by a decrease in voluntary activity. The total daily energy needs of an average-sized 7-year-old dog may decrease by as much as 20% when compared with its needs as a young adult. If food intake does not decrease proportionately with the decreasing energy needs, weight gain results.26 The end result is an increasing prevalence of obesity in older dogs. In short, a reduced metabolic rate associated with aging predisposes dogs to being overweight or obese.27

Neutering

Neutering results in the net loss of circulating sex hormones, slowing an animal's metabolism and predisposing the neutered animal to becoming overweight or obese.14,15,28 Changes in sex hormones after neutering directly affect the satiety center in the brain through changes in leptin and ghrelin concentrations and possibly indirectly affect it by altering cell metabolism and hormonal regulators of food.24,29-31

Gonadectomy in dogs also results in modified feeding patterns. Compared with before surgery, four female ovariectomized beagles fed ad libitum for three months after surgery ate significantly more food and gained more weight.28 The study suggested that energy intake should be reduced by 30% after ovariectomy to maintain optimal body weight for a period of six months.28 These results confirmed those of a previous experiment that also used four young adult female beagles and showed that energy requirements are 20% lower after ovariectomy.31

Medications

Certain medications may also contribute to obesity in dogs. Phenobarbital, a common anticonvulsant, causes polyphagia at high serum concentrations. The increase in food consumption may contribute to a worsening body condition, resulting in an overweight or obese dog. Glucocorticoids stimulate gluconeogenesis and abdominal lipogenesis, which may contribute to fat deposition and weight gain.

Adipokines

Excessive white adipose tissue impacts canine health through two main mechanisms. First, excessive fat deposition may have physical effects on the body, including excessive weight bearing, which worsens orthopedic diseases; constriction of upper airways, which exacerbates respiratory disorders; an inability to groom, which leads to dermatologic issues; and an insulating effect, which causes reduced heat dissipation. Second, the normal endocrine function of white adipose tissue may be disturbed, a now-recognized significant pathogenetic mechanism for the development and exacerbation of many of the obesity-associated metabolic disorders in both humans and domestic animal species.32


Table 1: Common Adipokines in Dogs*
White adipose tissue is an active endocrine organ, secreting protein modulators called adipokines (Table 1).33-37 Adipokines have proven endocrine, autocrine, and paracrine roles, regulating energy balance, immune function, angiogenesis, glucose and lipid metabolism, and hemostasis in people, dogs, and cats.34,38-40 Proinflammatory adipokines secreted by white adipose tissue increase as tissue mass rises. Thus, obesity may be viewed as a state of chronic inflammation. Increases in inflammatory adipokines have been causally linked to the development of metabolic syndrome and other obesity-related disorders in people.37,40 Increased inflammatory adipokine gene expression has also been documented in canine white adipose tissue.20


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Source: VETERINARY MEDICINE,
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