Importance of Obesity as a Disease
Obese humans generally do not live as long as their lean counterparts, and are much more likely to suffer from obesity-related diseases such as type II diabetes, coronary artery disease, osteoarthritis, hypertension, and some cancers. Cats are susceptible to the many of the same detrimental effects, including decreased longevity, orthopedic disease, diabetes, and cancer (1-3).
It has been estimated that up to a third of cats are overweight or grossly obese, with the highest rates seen in middle-aged cats (4,5). However, owners may not recognize that their cat is overweight, nor be aware of the associated health risks.
Obesity, a Major Endocrine Disease!
The expansion of adipose tissue was long thought to be simply a depot for the deposition of fatty acids (triglycerides) that occurred because of the excess energy intake (see Figure 1a).
However, research in the past decade has revealed that adipose tissue is not just a storage site, but also is responsible for production of many key hormones (e.g. leptin and adipokines) involved in energy balance and a variety of other processes (Figure 1b).
In other words, adipose tissue turns out to be an endocrine gland — in fact, its the largest endocrine gland in the body, secreting the largest number of obesity hormones (3,6,7)!
What does this mean for the obese cat? Obesity is a metabolic disease that results in major changes in appetite control (they are more hungry), energy expenditure (their metabolic rate is lower, thus they need to eat less), and induces a chronic, low-grade, pro-inflammatory state that may be responsible for many of the diseases associated with increased body weight (3,6-8)
Feline Obesity and Its Causes
The primary reason for development of obesity in any animal is that they are consuming more energy than they are expending. This can occur when a cat has excessive dietary intake of calories (e.g., high energy density food, excess food or treats offered) or when there is a reduction in energy expenditure (e.g., lower metabolism due to body weight or muscle mass, neuter status, or reduced activity, or illness or injury resulting in less exercise).
Recent studies indicate that greater than a third of all cats in the United States and Europe are obese, and this number likely underestimates the depth and breadth of the problem (3-5). There are a number of factors that contribute to feline obesity, including the following:
- Sex and neuter status (male vs. female; intact vs. castrated or spayed). Neutering is an important risk factor due to the hormonal changes that occur that result in changes in levels of leptin, progestins, and other hormones that result in increased appetite, and reduced energy metabolism and metabolic rate (9-11). The key factors for prevention of obesity in neutered animals appears to be careful control of intake immediately after neutering (no free choice feeding, reduction of intake by 25% to account for the hormonal changes resulting in reduced energy needs), and close monitoring of body weight and BCS to allow adjustments in intake if needed (3,11-13).
- Activity (indoor vs. outdoor). In indoor cats, reduced energy expenditure is a very important problem, and this is compounded by the fact that it is not easy to increase energy expenditure in cats like dogs with directed exercise (2,3,12,13).
- Feeding style (meal feeding vs free choice; canned vs dry food). When feeding free choice dry food, the risk of overfeeding, even in very small amounts is very high (2,3,12,13). In either case, the primary reason that weight gain occurs in cats is that they have a positive energy balance and this must be changed to affect weight loss.
Obesity and the Composition of the Diet: Frequently Ignored
Another factor that is important to consider, both in the development and treatment of obesity, is the role of carbohydrates (carbs) in the diet – not because carbs themselves are directly associated with fat (although excess carbs are stored as fat), but because of the effect on protein levels in the diet (13-15).
The higher the concentration of carbs in the diet, the lower the intake of protein. This results in a lower-than-needed intake of protein for maintenance and energy.
In my next post, we'll continue this topic of obesity in cats, and discuss why low carb, higher protein diets may be the best.
- Zoran DL, Buffington CAT. Effects of nutritional factors and lifestyle choice on the health and well-being of indoor cats. Journal of the American Veterinary Medical Association 2011;239:596-606.
- Laflamme DP. Understanding and managing obesity in dogs and cats. Veterinary Clinics of North America Small Animal Practice 2006;36:1283-1295.
- Zoran DL. Obesity in dogs and cats: a metabolic and endocrine disorder. Veterinary Clinics of North America Small Animal Practice 2010;40:221-239.
- Courcier EA, O'Higgins R, Mellor DJ, et al. Prevalence and risk factors for feline obesity in a first opinion practice in Glasgow, Scotland. Journal of Feline Medicine and Surgery 2010;12:746-753.
- Colliard L, Paragon BM, Lemuet B, et al. Prevalence and risk factors of obesity in an urban population of healthy cats. Journal of Feline Medicine and Surgery 2009;11:135-140.
- Lusby AL, Kirk CA, Bartges JW. The role of key adipokines in obesity and insulin resistance in cats. Journal of the American Veterinary Medical Association 2009;235:518-522.
- Kil DY, Swanson KS. Endocrinology of obesity. Veterinary Clinics of North America Small Animal Practice 2010;40:205-219.
- German AJ, Ryan VH, German AC, et al. Obesity, its associated disorders and the role of inflammatory adipokines in companion animals. Veterinary Journal 2010;185:4-9.
- Martin L, Siliart B, Dumon H, et al. Leptin, body fat content and energy expenditure in intact and gonadectomized adult cats: a preliminary study. Journal of Animal Physiology and Animal Nutrition 2001;85:195-199.
- Alexander LG, Salt C, Thomas G, et al. Effects of neutering on food intake, body weight and body composition in growing female kittens. British Journal of Nutrition 2011;106 Suppl 1:S19-23.
- Mitsuhashi Y, Chamberlin AJ, Bigley KE, et al. Maintenance energy requirement determination of cats after spaying. British Journal of Nutrition 2011;106 Suppl 1:S135-138.
- Michel K, Scherk M. From problem to success: feline weight loss programs that work. Journal of Feline Medicine and Surgery 2012;14:327-336.
- Zoran DL. Protein: the key to metabolism, health, and management of obesity in cats. 2012 OVMA Conference Proceedings. http://www.ovma.org/pdf/sa_program_clinicalpearls.pdf
- Vasconcellos RS, Borges NC, Goncalves KN, et al. Protein intake during weight loss influences the energy required for weight loss and maintenance in cats. Journal of Nutrition 2009;139:855-860.
- Wei A, Fascetti AJ, Liu KJ, et al. Influence of a high-protein diet on energy balance in obese cats allowed ad libitum access to food. Journal of Animal Physiology and Animal Nutrition 2011;95:359-367.