Obesity in the dog and cat

The states of being overweight and obese are characterized by an excessive accumulation of adipose tissue as a result of a surplus intake of energy compared with the amount actually needed. Being overweight is the most common form of malnutrition in pets in the industrialised world. The prevalence of this problem is approximately the same in all developed countries and seems to be increasing in recent years (Table 1).

Table 1. Prevalence of overweight animals in different countries. 

Defining when an animal has an optimal body state or is overweight or obese is not as simple as it might seem. Body weight can be a help, since accumulation of adipose tissue causes an increase in weight, but it is important to remember that a weight increase can be related to an accumulation of any type of tissue (e.g., muscle hypertrophy in athletes) or fluids (e.g., ascites). Nevertheless, in most cases an increase in weight is related to an increase in adipose tissue. One of the most widely used methods in veterinary medicine to determine whether an animal is overweight or obese is the Body Condition Score (Figs. 1 and 2). 

The causes of an imbalance between energy intake and energy expenditure are still not completely understood. In normal conditions complex homeostatic mechanisms involving nerves, hormones and biochemical, behavioural, environmental and genetic factors should maintain the intake of energy and body composition at given “set points”._¹² When these mechanisms fail to maintain an equilibrium a positive energy balance develops, which leads to the accumulation of adipose tissue.

RISK FACTORS

There are various types of risk factors for the development of an imbalance between energy intake and energy consumed; these can be divided into genetic, environmental (nutritional and infective) and individual (age, gender, reproductive status, amount of physical activity and behavioural factors). Although it is known that there are predisposing genetic factors, the animal with these factors only becomes overweight/obese if environmental factors cause expression of the phenotype.

Genetic factors
Various different genetic factors influence the risk of becoming overweight/obese._¹⁶ There is a breed predisposition, with a higher prevalence of overweight animals among the Labrador and Golden Retriever, Cairn Terrier, Cocker Spaniel, Long-haired Dachshund, Shetland Sheepdog, Basset Hound, Cavalier King Charles Spaniel, Pug, Dalmatian and Beagle than among other breeds._^4,9,17 In contrast, there is no breed predisposition to becoming overweight in cats._¹⁸Some genes have been related to obesity. Compared with lean Beagles, overweight Beagles have higher expression of genes associated with the metabolism of fatty acids and purines. Furthermore, overweight Beagles have lower expression of genes associated with the metabolism of nucleotides, carbohydrates and amino acids, the breakdown of branched chain amino acids, receptor signalling for insulin and lipid metabolism._¹⁹

Environmental factors
Nutrition. There are various dietary risk factors. The most important is obviously the administration of excessive amounts of palatable food with a high energy content. The fact that the food is palatable, combined with a lack of control of the portions, leads to an excessive intake of energy. This is aggravated by the fact that the owner often chooses the diet for his or her animal based exclusively on its palatability._¹³ Foods with a high energy content (> 14% of fats) and those that are very palatable must be carefully rationed, especially in greedy animals and those genetically predisposed to put on weight.

Physical activity. Most pets live in a house and often have insufficient exercise. Physical activity is the most variable component of energy expenditure but it is the one that can make the largest contribution to increasing energy consumption. Studies have confirmed that the risk of obesity decreases for every additional hour of exercise during the week._²⁰ It is not, therefore, surprising that animals with a limited possibility of exercising are at higher risk of becoming obese._¹⁸ Unfortunately, most owners consider their dogs moderately or very active._²¹ Other variables that can decrease spontaneous activity and, therefore, influence energy expenditure are moving to a smaller flat and musculo-skeletal disorders._²¹

Infections. Some viruses have been implicated as causes of obesity in both humans and animals._^22,23 However, the effects have been demonstrated in most cases in laboratory animals._²⁴  Distemper virus is capable of impairing the function of the hypothalamus, leading to obesity._²⁵

Individual factors
Age. Several studies have related age with the prevalence of overweight dogs and cats._^9,18,26The prevalence of obesity is higher in both dogs and cats between the ages of 5 to 11 years._^27,28 After 12 years old, the prevalence tends to decrease._^18,26 These observations have led to two theories on obesity and ageing. One theory is based on the hypothesis that ageing causes changes in digestive mechanisms and, therefore, if the diet is not changed, the animal will gain weight. The other theory is based on the fact that overweight/obese subjects have a shorter life expectancy and, therefore, the population over 12 years old is formed mainly of animals that have had an ideal body condition throughout their life, also because an inverse correlation has been demonstrated between calorie intake and life expectancy in Labradors._^26,29

Gender and reproductive status. There are reported differences in body composition between sexually intact and sterilised cats_³⁰ and in energy intake between sexually intact males and females (probably due to different amounts of lean body mass)._^30,31 It has been estimated that the amount of adipose tissue in females is, on average 16% greater than in males._³²The prevalence of overweight animals is higher among females_^4,9 and sterilisation increases the risk in both dogs and cats._^11,28,33-35 The energy requirements of spayed cats are 20-25% lower than those of sexually intact cats of the same age (measured by indirect calorimetry) (Root et al., 1996). This is due, in part, to a decrease in basal requirement because of the loss of oestrogens or androgens and, in part, to decreased spontaneous activity._^36,37

Owner’s life style. The prevalence of overweight animals is higher among dogs belonging to owners who are, in their turn, also overweight (44% compared to 25%) or elderly (36% versus 20%)._³⁸ The reason for these differences is that the level of the owner’s physical activity influences that of their dogs. Furthermore, the owners of overweight animals have a strong tendency to ”humanise” their animals and establish a type of relationship based on the administration of food rather than on other interactions, such as playing._⁸

CONSEQUENCES

The major clinical problems of obesity are those related to the numerous associated consequences such as orthopaedic disorders, endocrine disorders, hyperlipidaemia, cardiorespiratory diseases, hypertension, neoplasms and disorders of the integument, reproductive system and urinary tract. Furthermore, it seems that there is a correlation between excess weight/obesity and morbidity and shorter life expectancy._⁶ The numerous pathophysiological variations that occur in obese animals include pharmacokinetic and pharmacodynamic alterations (from an anaesthesiological point of view these animals have a higher risk of post-operative complications).

In human medicine it is thought that adipocytokines may play a role in the pathogenesis of many of the associated clinical disorders and it is probable that there are also similarities with veterinary medicine. Thus, the clinical consequences of obesity seem to have a dual aetiopathogenic mechanism: on the one hand there is overloading of various apparatuses and on the other hand a chronic inflammatory state that could lead to tissue degeneration._⁷

PREVENTION AND TREATMENT

The therapeutic plan currently available to the veterinarian is primarily based on correct rationing of food with possible addition of nutrients or particular raw materials and also adjunctive drug treatment (mitratapide, dirlotapide)._^14,15

The basis of correct rationing starts with the calculation of the patient’s maintenance energy requirements which are then reduced by 20-30%. The calorie intake calculated in this way can be supplied by giving the animal a smaller amount of food or by giving it the same amount of food but with a lower energy content, so-called “light” food, which has the advantage of allowing the intake of more food. The foods that can be given to overweight animals are based fundamentally on two principles:

• a higher percentage of proteins, which increases the digestive metabolic work and, therefore, energy expenditure;
• a higher percentage of fibre, which causes a lower energy density and should have the effect of giving satiety. Experimental studies have shown that this is the case in cats_⁴¹ but not in dogs (which, despite the high levels of fibre, eat large amounts of energy if the food is not rationed)._⁴²

There are also nutrients that, based on published data, it could be interesting to include in food rations for overweight animals. These nutrients include L-carnitine,_^43,44 conjugated linoleic acid_⁴⁵and some substances derived from plants such as Phaseolus vulgaris_^46,47 and Garcinia cambogia._⁴⁵

The success of preventive measures is strongly related to the veterinarian’s ability to educate and convince the owner about the dietary practices to adopt for his or her animal and the periodic controls that should be performed. These efforts must be concentrated particularly on the owners of those subjects that the environment and family history or the literature suggest are particularly predisposed.

Prevention of weight gain/obesity is undoubtedly the most effective management because it is difficult to lose adipose tissue when a large amount of body fat has been maintained for a certain period of time._^39,40 This is due, in part, to changes in the activity of lipoprotein lipase (LPL). After digestion and absorption, the fat derived from the diet is transported into adipose tissue by chylomicrons. LPL is an enzyme found in capillaries which has the function of removing the fat from chylomicrons and carrying it in the circulating blood. LPL hydrolyses the triglycerides in free fatty acids and glycerol. The fatty acids enter adipocytes were they are re-esterified into triglycerides and stored. When needed for energy, the stored triglycerides are newly hydrolysed to fatty acids and glycerol by hormone-sensitive lipase and re-enter the bloodstream. The levels of LPL increase during periods of weight gain in both obese and non-obese subjects. However, after a loss of weight, while the levels of LPL return to normal in non-obese subjects, they remain high in obese ones. This is probably one of the factors that contributes to a rapid regain of weight in chronically obese patients.

Being overweight/obese remains a disease with one of the highest therapeutic failure rates and highest recurrence rates, because of the strong psychological component involved in the human-animal relationship._⁸

References

1. Burkholder WJ, Toll PW, (2000), Obesity. In: Hand, M.S., Thatcher C.D., Remillard R.L., Roudebush P. (Eds.), Small Animal Clinical Nutrition IV. Topeka, KS: Mark Morris Associates, pp. 401-430.
2. Colliard L, Ancel A, Benet J-J, Paragon B-M, Blanchard G, (2006), Risk factors for obesity in dogs in France. J. Nutr. 136, 1951S-1954S.
3. Donoghue, S., Khoo, L., Glickman, L.T., Kronfeld, D.S., (1991).Body condition and diet of relatively healthy older dogs. J Nutr. 121, S58-S59.
4. Edney AT, Smith PM, (1986), Study of obesity in dogs visiting veterinary practices in the United Kingdom. Vet. Rec.118, 391-6.
5. Mussa PP, Prola L, Meineri G, (2006), Obesity in dog: a survey results in Italy. Proceedings of the 10^th ESVCN Congress – Nantes (France), 5-7 October 2006.
6. Weindruch R, Walford RL (1988) The retardation of aging and disease by dietary restriction. Charles C. Thomas, Springfield IL .
7. Budsberg S, (2006) Nutrition and Osteoarthritis in Dogs: Does It Help? Veterinary Clinics of North America: Small Animal Practice, 36 (6), 1307-1323.
8. Kienzle E, Bergler R, Mandernach A (1998) A comparison of the feeding behavior and the human-animal relationship in owners of normal and obese dogs. J Nutr. Dec;128(12 Suppl):2779S-2782S.
9. Mason E. (1970) Obesity in pet dogs. Veterinary Record; 86: 612-616.
10. Robertson ID. (2003) The association of exercise, diet and other factors with owner-perceived obesity in privately owned dogs from metropolitan Perth, Western Australia. Preventive Veterinary Medicine; 58: 75-83.
11. McGreevy PD, Thomson PC, Price C, et al. (2005) Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved. Veterinary Record; 156: 695-702.
12. Druce M., Bloom S.R. (2003). Central regulators of food intake. Current Opinion in Clinical and Metabolic Care; 6: 361-367.
13. Prola L., Mussa P.P. (2010). Prevencion de la obesidad canina a través de un estilo de vida saludable. Canis et Felis; 106: 60-72.
14. Wren JA, Gossellin J, Sunderland SJ (2007). Dirlotapide: a review of its properties and role in the management of obesity in dogs. Journal of Veterinary Pharmacology and Therapeutics; 30: 11–16.
15. DobeneckerB, De BockM, EngelenM, GoossensL, ScholzA, KienzleE (2009) Effect of mitratapide on body composition, body measurements and glucose tolerance in obese Beagles. Veterinary Research Communications; 33(8): 839-847.
16. Buffington CA, Holloway C, Abood SK. Clinical Dietetics. In: Manual of Veterinary Dietetics. St. Louis, MO: Elsevier/Saunders, 2004; 49-141.
17. LundEM. Overweight pets: What’s the big deal? Banfield’s DataSavant. Portland, OR, 2007; 3(2): 16-20.
18. Scarlett JM, Donoghue S, Saidla J, et al. Overweight cats: Prevalence and risk factors. International Journal of Obesity 1994; 18 (Suppl. 1): S22-S28.
19. Yamka RM, Friesen KG, Gao X, et al. Identification of genes related to obesity in dogs. Federation of American Societies for Experimental Biology Journal 2007a; 21: 28.4 (A4).
20. Robertson ID. The association of exercise, diet and other factors with owner-perceived obesity in privately owned dogs from metropolitan Perth, Western Australia. Preventive Veterinary Medicine 2003; 58: 75-83.
21. Slater MR, Robinson LE, Zoran DL, et al. Diet and exercise patterns in pet dogs. Journal of the American Veterinary Medical Association 1995; 207: 186-190.
22. Atkinson RL. Viruses as an etiology of obesity. Mayo Clinic Proceedings 2007; 82(10): 1192-1198.
23. Atkinson RL. Could viruses contribute to the worldwide epidemic of obesity? International Journal of Pediatric Obesity 2008; 3: 37-43.
24. DhurandharNV. Infectobesity: Obesity of infectious origin. Journal of Nutrition 2001; 131 (Suppl.): 2791S-2797S.
25. Verlaeten O, Griffond B, Khuth ST, et al. Down regulation of melanin concentrating hormone in virally induced obesity. Molecular and Cellular Endocrinology 2001; 181: 207-219.
26. Armstrong PJ, Lund EM. Changes in body composition and energy balance with aging. Veterinary Clinical Nutrition 1996; 3: 83-87.
27. Lund EM, Armstrong PJ, Kirk CA, et al. Prevalence and risk factors for obesity in adult dogs from private veterinary practices. International Journal of Applied Research in Veterinary Medicine 2006, 4: 177-186.
28. Lund EM, Armstrong PJ, Kirk CA, et al. Prevalence and risk factors for obesity in adult cats from private veterinary practices. International Journal of Applied Research in Veterinary Medicine 2005; 3: 88-96.
29. Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction on life span and age-related changes in dogs. Journal of the American Veterinary Medical Association 2002; 220: 1315-1320.
30. Jewell DE, Kirk CA, Berryhill SA, et al. The effect of age on body composition in dogs and cats. In: Proceedings. Symposium on Health and Nutrition of Geriatric Cats and Dogs, Orlando, FL, January 1996: 52.
31. Klausen B, Toubro S, Astrup A. Age and sex effects on energy expenditure. American Journal of Clinical Nutrition 1997; 65: 895-907
32. Meyer H, Stadtfeld G. Investigations on the body and organ structure of dogs. In: Anderson RS, ed. Nutrition of the Dog and Cat. Oxford, UK: Pergamon Press, 1980; 15-30.
33. Jeusette IC, Daminet S, Nguyen P, et al. Effect of ovariectomy and ad libitum feeding on body composition, thyroid status, ghrelin and leptin plasma concentrations in female dogs. Journal of Animal Physiology and Animal Nutrition (Berlin) 2006; 90: 12-18.
34. Kanchuk ML, Backus RC, Calvert CC, et al. Weight gain in gonadectomized normal and lipoprotein lipase-deficient male domestic cats results from increased food intake and not decreased energy expenditure. Journal of Nutrition 2003; 133: 1866-1874.
35. Scott KC, Levy JK, Gorman SP, et al. Body condition of feral cats and the effect of neutering. Journal of Applied Animal Welfare Science 2002; 5: 203-213.
36. Hart BL, Barrett RE. Effects of castration on fighting, roaming, and urine spraying in adult male cats. Journal of the American Veterinary Medical Association 1973; 163: 290-292.
37. Hopkins GS, Schubert TA, Hart BL. Castration of adult male dogs: Effects on roaming, aggression, urine marking, and mounting. Journal of the American Veterinary Medical Association 1976; 168: 1108-1110.
38. Hand M.S. Obesity: occurence, treatment and prevention. Veterinary clinics of north america, 1989 19: 447-469.
39. Laquatra I. Nutrition for weight management. In: Mahan LK, Escott-Stump S, eds. Krause’s Food, Nutrition, and Diet Therapy, 10th ed. Philadelphia, PA: WB Saunders, 2000; 485-515.
40. Nagaoka D., Mitsuhashi Y., Angell R., Bigley K.E., Bauer JE. 2009. Re-induction of obese body weight occurs more rapidly and at lower caloric intake in beagles. Journal of Animal Physiology and Animal Nutrition; 94:287-292
41. Prola L., Dobenecker B., Kienzle E. 2006. Interaction between Dietary Cellulose Content and Food Intake in Cats. J. Nutr. 136: 1988S–1990S.
42. Dobenecker B, Kienzle E. Interactions of cellulose content and diet composition with food intake and digestibility in dogs. J Nutr. 1998;128:2674S–5.
43. Gross KL, Zicker SC, 2000. L-carnitine increases muscle mass, bone mass, and bone density in growing large breed puppies. J Anim Sci  ;78 :176.
44. Sunvold GD, Tetrick MA, Davenport GM, Bouchard GF, 1998. "Carnitine supplementation promotes weight loss and decreased adiposity in the canine", Proceedings of the XXIII World Small Animal Veterinary Association, p. 746.
45. Leray V, Dumon H, Martin L, Siliart B, Sergheraert R, Biourge V, Nguyen P, 2006. No Effect of Conjugated Linoleic Acid or Garcinia cambogia on Fat-Free Mass, and Energy Expenditure in Normal Cats. J. Nutr. 136: 1982S–1984S.
46. KotaruM, Yoshikawa H, Ikeuchi T, Saito K, Iwami K & Ibuki F (1987). An a-amylase inhibitor from cranberry bean (Phaseolus vulgaris): its specificity in inhibition of mammalian pancreatic a-amylases and formation of a complex with the porcine enzyme. J Nutr Sci Vitaminol (Tokyo) 33, 359–367.
47. Obiro WC, Zhang T, Jiang B (2008). Thenutraceutical role of the Phaseolus vulgaris a-amylase inhibitor. British Journal of Nutrition100: 1–12