Obesity in dogs and cats

Obesity is defined as excessive fat deposition in the body. It is one of the most important and widespread diseases of dogs and cats and is accompanied by a variety of other health disorders. Not only is there increased stress and wear on the musculoskeletal and cardiovascular systems, but adipose tissue also functions as an endocrine organ that secretes biologically active substances of a pro-inflammatory nature. These may then contribute to the development of a number of chronic inflammatory diseases. Numerous studies have shown that 30 to 60 % of the adult population of dogs and cats in developed countries are overweight or obese. The main cause of obesity is excessive energy intake from food in excess of need, and no differences have been found between feeding kibble, commercial wet food or home-made diets. Excess energy obtained from digested carbohydrates, fats and proteins is stored in the body as stored fat. In terms of nutrient composition, feeds rich in fat and digestible carbohydrates, which are easily digested and converted into fat stores, are particularly risky. Excess protein is also converted to fat as a result, but its metabolism is somewhat more complex and more demanding on the body. Moreover, it is a process that consumes energy at the same time. In addition to excessive energy intake from feed, lack of exercise can also influence the development of obesity. Movement increases energy expenditure and at the same time contributes to the development of muscle mass. Muscle tissue, unlike adipose tissue, is highly metabolically active and increases resting energy requirements. Castration is another significant risk factor in the development of obesity. Neutered dogs and cats have been found to be approximately 2 times more likely to develop obesity than unneutered dogs and cats. Neutering reduces energy requirements and metabolic rate, with energy requirements decreasing by up to 30% in dogs and 20-25% in cats after neutering. Neutering also often results in reduced physical activity and changes in eating behaviour towards increased food intake. According to one recent study, the effect of neutering on the development of obesity is more pronounced in males than in females. A decrease in energy requirements and thus an increase in the risk of obesity also occurs at older ages, with a decrease in energy requirements of about 20% in dogs and less pronounced in cats. However, very old dogs may have problems with weight loss and poorer fitness, so this trend cannot be taken as a blanket. The risk of obesity may be higher in certain dog breeds, e.g. retrievers, spaniels, beagles, dachshunds, pugs and some terriers. Only a small percentage of obesity may be caused by a hormonal disorder such as low thyroid function or Cushing's syndrome. Certain medications, especially glucocorticoids and antiepileptic drugs, can also affect the development of obesity. Storage fat accumulates mainly in certain places in the body and this is then used in the diagnosis of obesity. Dogs store subcutaneous fat in the back, loin and sacrum, cats mainly in the skin folds on the lower abdomen and cheeks. Research on body composition has found that in optimal condition, a dog or cat should have 15-20% stored fat. When overweight, the proportion of body fat tends to be around 30%, when obese 40% or more. For a basic assessment of condition, the so-called relative body weight (RBW) is used, the current weight of the animal divided by its ideal weight. For most cats, the ideal weight is between 2.5-6.5 kg, but there is much more variability in dogs, so determining ideal weight can be problematic. For purebreds, the weight given in the breed standard can be used, for crossbreeds the average weight of breeds similar in size and conformation can be used. An RBW of 1.1-1.2 (10-20 % above ideal weight) is overweight and an RBW above 1.2 (more than 20 % above ideal weight) is obese. A more accurate assessment is based on an assessment of the body silhouette and fat deposits in selected areas, independent of weight, and classification into an appropriate grade based on the Body Condition Score (BCS) scale. The BCS uses well-defined criteria that can be determined by visual assessment and palpation. Body contours and silhouette from the side and above, palpability or visibility of bony prominences and ribs, and amount of abdominal fat are assessed. A nine-point scale is most commonly used in veterinary practice, or a five-point scale, which is simpler. On a nine-point scale, a grade of 1-3 indicates malnutrition, 4-5 optimal condition, 6-7 overweight and 8-9 obesity. Each grade represents a weight change of about 10%. A dog with a BCS of 7/9 will therefore weigh 20% more than its optimum weight. When assessing body condition, the animal's body is first examined from above and from the side. For long-haired animals with a rich coat, palpation is necessary. This tends to be more difficult in cats than in dogs, as they are usually less cooperative. A dog and cat in optimum condition should have a tapered mid-body, with a distinct waistline visible behind the ribs. When viewed from the side, the dog's abdomen should be drawn in, taking into account the breed-specific body structure. In the cat, the abdomen should not be flabby, with a pronounced overhanging skin fold. The next step is to run both hands over the rib cage and feel for palpability of the ribs. In a dog or cat in optimal condition, the ribs should be easily palpable and not covered by excess fat. In overweight cats, the ribs may still be palpable, but with some difficulty because they are covered by a layer of fat. In obese animals, the ribs are not palpable at all and are covered by a thick layer of fat. The waistline is not distinct and the abdomen tends to be protuberant. The BCS grade found can be used to estimate the percentage of body fat. An optimum fitness of 4-5/9 corresponds to 15-20% body fat, a change of one fitness level on a nine-point scale represents approximately 5% fat. Thus, a BCS of 7/9 will correspond to 30% body fat and a BCS of 9/9 to 40% or more body fat. Estimation of body fat percentage based on a correctly assessed BCS is reasonably accurate even when compared to objective laboratory methods where fat percentages were measured by instruments.

MVDr. Eva Štercová, Ph.D.