Nutritional Disease

Abstract

The World Health Organization's definition of obesity is an abnormal or excessive fat accumulation in adipose tissue to the extent that health is impaired. 1 -3 An excess of adipose tissue occurs when the caloric intake surpasses the caloric expenditure. 4 Owing to the prevalence of obesity in the human population, the World Health Organization has classified obesity into simple obesity (body mass index [BMI] 30-34.9 kg m −2 ), severe obesity (35-39.9 kg m −2 ), morbid obesity (40-49.9 kg m −2 ), and super morbid obesity (≥40 kg m −2 ). 5 PathophysiologyObesity is the most common medical condition in companion animals and is associated with a number of comorbidities. 2 Approximately 55% of dogs and 53% of cats in the USA are considered to be overweight or obese. 6 Worldwide, 22-40% of dogs are considered to be obese. 2 Coincident with obesity in humans comes an increase in morbidity, such as diabetes and musculoskeletal conditions. 6 The criteria for obesity are not as clear-cut in veterinary patients as with human patients, as optimal body weights have not been established for our species and varying breeds. However, it is still concluded that when a patient's weight is 15% above normal for its breed, it is "overweight," and when a patient's weight is 30% above normal, it is "obese." 2 Risk factors for the development of obesity in veterinary patients have been identified. There is a link between certain breeds and their genetic predisposition for obesity. genetically predisposed to obesity. Likewise, particular breeds appear to be resistant to obesity, such as the sight hound group. 2 Aging is associated with an increase in the likelihood of obesity. With aging, the lean body mass decreases, resulting in a decrease in the total daily energy needs of the animal. In conjunction with a decrease in total daily energy needs, the animal's voluntary activity is typically decreased, possibly because of comorbidities of aging, such as osteoarthritis. The decrease in total daily energy needs combined with a decrease in activity can lead to weight gain if caloric intake is not decreased as well. 2 Excessive weight can have a major impact on the overall health of the animal. In humans, morbid obesity (BMI of ≥ 40-44.9 kg m −2 ) is associated with an increased likelihood of diabetes mellitus, 7 respiratory failure, hypertension, left ventricular hypertrophy, atherosclerosis, myocardial ischemia, and some forms of cancer compared to nonobese patients. 4 Mild to moderate hypertension is described in up to 60% of obese human patients, whereas 5-10% of obese human patients have severe hypertension. With time, hypertension can lead to left ventricular dilation, increased left ventricular wall stress, compensatory left ventricular hypertrophy, and left ventricular diastolic dysfunction. 4 An increase in body adipose tissue alters cardiopulmonary physiology, leading to an increase in cardiac output (CO), oxygen consumption, and closing capacity and a decrease in functional residual capacity (FRC). In humans, these alterations ca...