How to Feed Cats with Diabetes: Part 2— Protein

Evolutionary events shaped the cat’s core metabolism such that their systems are uniquely set up to metabolize a diet which is high in moisture, high in protein, and very low in carbohydrates. Because this is the diet cats have relied upon for tens of thousands of years, they depend more on protein intake than omnivores (e.g., dogs and man) (1-3).

As I discussed in my last blog post (How to Feed Cats with Diabetes), cats do not have the ability to process carbohydrates very efficiently and show relative carbohydrate intolerance. This becomes extremely important when selecting a diet for cats with diabetes, and what is fed can play a key role in the successful management of the diabetic cat.

Weight Loss, Obesity, Muscle Wasting, and Sarcopenia— Common Features of Diabetes
At time of diagnosis of diabetes, weight loss is reported in about 70% of cats. However, cats are more often overweight or obese (40%) than of normal weight or underweight. In addition, muscle wasting and poor muscle condition scores are reported in about half of cats with diabetes.

One contributing factor for the muscle wasting seen in the diabetic cats is their age. The typical diabetic cat is a senior, with about 70% older than 10 years of age at time of diagnosis (4,5). Therefore, since most of these cats are older, they are also prone to develop sarcopenia (from the Greek meaning "poverty of flesh") which is commonly associated with aging. 

In human patients, Type 2 diabetes is associated with an increased risk of concurrent sarcopenia (8). In addition, because skeletal muscle is a primary site for insulin-mediated glucose uptake and deposition, sarcopenia (and especially sarcopenic obesity) (9) may promote insulin resistance, predisposing patients to development of type 2 diabetes and making existing diabetes more difficult to control (10,11).

We do not know if the loss of muscle mass alone (sarcopenia) or combined with weight gain (i.e., sarcopenic obesity) also contributes to the insulin resistance and hyperglycemia associated with the feline disorder. However, given that both obesity and some degree of muscle wasting are common in diabetic cats, it seems reasonable to assume that sarcopenia and sarcopenic obesity may indeed contribute to worsening of feline diabetes, as it does in man (8-11).

Management Goals of Feline Diabetes
In cats with diabetes, a primary goal of therapy is to feed a diet that will lessen postprandial hyperglycemia, reduce marked fluctuations of blood glucose concentrations, minimize the demand on beta cells to produce insulin, and improve insulin sensitivity (6,7,12). By doing this, we decrease the effect of “glucose toxicity” and hopefully allow the pancreatic islet cell to partially recover. In about half of newly diagnosed diabetic cats, this will lead to remission of the diabetic state (13-15). As I discussed last week, we can do this in our diabetic cats by feeding a diet low in carbohydrates.

A secondary goal of therapy is to provide a diet that will help normalize body weight and maintain and/or restore lost muscle mass (16,17), as discussed below.

Recommendations for Diabetic Cats: Higher Dietary Protein:
Because diabetes is a catabolic state, loss of muscle mass is common in cats with diabetes, even if their body condition score indicates overweight or obesity. In these cats, high-protein diets are essential to ensure replacement of any lost muscle mass. In addition, higher protein diets will help prevent the hepatic lipidosis from developing during induction of weight loss (needed in many diabetic cats), and are essential to increasing metabolism to help promote fat burning and normal insulin function (16-19).

Protein is the primary macronutrient responsible for maintenance of muscle mass (20,21). Restoring and preserving any remaining muscle tissue in diabetic cats, an obligate carnivore, depends upon the cat consuming a diet with sufficient amounts of high-quality protein (greater than 40% ME; greater than 10 g/100kcal). This higher than average protein level also helps restore and maintain lost muscle mass, since many diabetic cats will develop “sarcopenia” as they age.

Although it is important to implement a low-carbohydrate/high protein diet in the management of cats with diabetes as soon as possible, there are circumstances where this should be delayed or may be inappropriate (18). For example, in cats with advanced (IRIS stage 3-4) chronic kidney disease (CKD) requiring phosphorus restriction and a reduction in dietary protein, high-protein/low-carbohydrate diabetic diets may not be appropriate (19,22,23).

In cats with earlier stages of CKD, phosphorus should be restricted using other methods than changing to a protein-restricted/higher carb diet (if possible), because feeding higher amounts of carbohydrates would reduce the probability of remission. It is important to remember that over-the-counter low carbohydrate cat foods often contain predominantly fish or meat and tend to have substantially higher phosphate levels than some of the veterinary prescription diets designed for diabetes.

References:

1. MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Annu Rev Nutr 1984;4:521-562. 
2. Zoran DL. The carnivore connection to nutrition in cats. J Am Vet Med Assoc 2002;221:1559-1567. 
3. Eisert R. Hypercarnivory and the brain: protein requirements of cats reconsidered. J Comp Physiol B 2011;181:1-17. 
4. Farrow H, Rand JS, Morton JM, et al. Postprandial glycemia in cats fed a moderate carbohydrate meal persists for a median of 12 hours -- female cats have higher peak glucose concentrations. J Feline Med Surg 2012;14:706-715. 
5. Farrow HA, Rand JS, Morton JM, et al. Effect of dietary carbohydrate, fat, and protein on postprandial glycemia and energy intake in cats. J Vet Intern Med 2013;27:1121-1135. 
6. Rand JS. Feline diabetes mellitus In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Fourth ed. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;133-147.
7. Baral RM, Little SE. Endocrine pancreatic disorders In: Little SE, ed. The Cat: Clinical Medicine and Management. St. Louis: Elsevier Saunders, 2012;547-571.
8. Kim TN, Park MS, Yang SJ, et al. Prevalence and determinant factors of sarcopenia in patients with type 2 diabetes: the Korean Sarcopenic Obesity Study (KSOS). Diabetes Care 2010;33:1497-1499. 
9. Stenholm S, Harris TB, Rantanen T, et al. Sarcopenic obesity: definition, cause and consequences. Curr Opin Clin Nutr Metab Care 2008;11:693-700. 
10. Srikanthan P, Hevener AL, Karlamangla AS. Sarcopenia exacerbates obesity-associated insulin resistance and dysglycemia: findings from the National Health and Nutrition Examination Survey III. PLoS One 2010;5:e10805. 
11. Moon SS. Low skeletal muscle mass is associated with insulin resistance, diabetes, and metabolic syndrome in the Korean population: The Korea National Health and Nutrition Examination Survey (KNHANES) 2009-2010. Endocr J 2013. 
12. Zini E, Osto M, Franchini M, et al. Hyperglycaemia but not hyperlipidaemia causes beta cell dysfunction and beta cell loss in the domestic cat. Diabetologia 2009;52:336-346. 
13. Zini E, Hafner M, Osto M, et al. Predictors of clinical remission in cats with diabetes mellitus. J Vet Intern Med 2010;24:1314-1321. 
14. Reusch CE, Hafner M, Tschuor F, et al. Diabetes remission in cats: a review. Schweiz Arch Tierheilkd 2011;153:495-500. 
15. Gottlieb S, Rand JS. Remission in cats: including predictors and risk factors. Vet Clin North Am Small Anim Pract 2013;43:245-249. 
16. Nguyen P, Leray V, Dumon H, et al. High protein intake affects lean body mass but not energy expenditure in nonobese neutered cats. J Nutr 2004;134:2084S-2086S. 
17. Keller U. Dietary proteins in obesity and in diabetes. Int J Vitam Nutr Res 2011;81:125-133. 
18. Zoran DL, Rand JS. The role of diet in the prevention and management of feline diabetes. Vet Clin North Am Small Anim Pract 2013;43:233-243. 
19. Frank G, Anderson W, Pazak H, et al. Use of a high-protein diet in the management of feline diabetes mellitus. Vet Ther 2001;2:238-246. 
20. Paddon-Jones D, Short KR, Campbell WW, et al. Role of dietary protein in the sarcopenia of aging. Am J Clin Nutr 2008;87:1562S-1566S. 
21. Wakshlag JJ. Dietary protein consumption in the healthy aging companion animal. Proceedings of the Nestlé Purina Companion Animal Nutrition Summit: Focus on Gerontology 2010;32-39.
22. Kidder AC, Chew D. Treatment options for hyperphosphatemia in feline CKD: what's out there? J Feline Med Surg 2009;11:913-924. 
23. Ross SJ, Osborne CA, Kirk CA, et al. Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. J Am Vet Med Assoc 2006;229:949-957. 

How to Feed Cats with Diabetes

Diet plays a key role in the successful management of the diabetic cat. Because cats are obligate carnivores (1-3), diabetic cats are relatively carbohydrate intolerant and respond best to a low carbohydrate diet. This differs from dogs, which are omnivores and are quite tolerant of a moderate to high carbohydrate meal, even when diabetic (4,5).

Evolutionary events shaped the cat’s core metabolism such that their systems are uniquely set up to metabolize a diet which is high in moisture, high in protein, and very low in carbohydrates. Because this is the diet they have relied upon for tens of thousands of years, they do not have the ability to process carbohydrates very efficiently and show relative carbohydrate intolerance (1-3). This becomes extremely important when selecting a diet for cats with diabetes.

Postprandial Glycemia in Man, Dogs, and Cats
As a result of these differences, plasma glucose clearance rates are longer in cats compared to dogs or humans after feeding a moderate to high carbohydrate meal — in other words, even normal cats have much more prolonged postprandial period of hyperglycemia than might be expected. In healthy humans and dogs, postprandial hyperglycemia normally persists for 2 to 6 hours (4,6).

In contrast, recent studies of healthy cats found that both serum glucose and insulin concentrations remained significantly increased for a median time of 12 hours following ingestion of a moderate carbohydrate meal (25% of calories), and that both glucose and insulin concentrations remained above baseline values for 24 hours in approximately 20% of the cats (7,8). Most feline diets contain even higher amounts of carbohydrate (greater than 25%) and, therefore, would be expected to result in more severe postprandial hyperglycemia and a longer time to return to baseline.

Management Goals of Feline Diabetes
In cats with diabetes, a primary goal of therapy is to feed a diet that will lessen postprandial hyperglycemia, reduce marked fluctuations of blood glucose concentrations, minimize the demand on beta cells to produce insulin, and improve insulin sensitivity (9-11). By doing this, we decrease the effect of “glucose toxicity” and hopefully allow the pancreatic islet cell to partially recover. In about half of newly diagnosed diabetic cats, this will lead to remission of the diabetic state (12-14).

A secondary goal of therapy is to provide a diet that will help normalize body weight and maintain and/or restore lost muscle mass (15,16). I'll be covering the reason why higher protein diets are also important for diabetes in my post next week.

Recommendations for Diabetic Cats: Low Dietary Carbohydrates:
It is well accepted dogma, at least by most practicing veterinarians who specialize in feline medicine, that feeding a low-carbohydrate diet is the mainstay in the treatment of diabetes mellitus, especially if remission of the diabetic state is the goal. In accord with that, there is strong clinical and research evidence that a diet containing very low concentrations of carbohydrate (e.g., carbohydrates less than 12% of calories) is the most effective means for achieving our nutritional goals for cats with diabetes (5,9,17-19).

Feeding a low carbohydrate diet will improve insulin sensitivity, help stabilize glucose metabolism, and can reduce or eliminate the need for exogenous insulin in these cats (5,20,13,14).  The likely mechanism for these observations is relatively simple —decreasing dietary carbohydrate load reduces the postprandial blood glucose elevation, which in cats is prolonged, sometimes lasting for over 12 hours (7,8).

In some diabetic cats, decreasing carbohydrate content to a level significantly less than 12% of the daily calories may help increase their rate of remission. In accord with that, the highest remission rates (greater than 80%) have been reported feeding diets with approximately 6% of energy from carbohydrate (21).

If a change in feeding to a low-carbohydrate diet is made in a diabetic cat already stabilized on insulin, it is extremely important to realize that this will result in a lowered daily insulin dosage — often significantly (9.20). If not closely monitored—ideally with home glucose testing— severe hypoglycemia can develop in these cats because they become more sensitive to insulin after the diet composition is changed.

Therefore, when changing from a higher-carbohydrate to a low-carbohydrate diet, we recommend initially reducing the insulin dose by 30% to 50% to help avoid hypoglycemia. If the diabetic cat goes into remission (no more insulin needed to maintain euglycemia), we recommend maintaining the low-carbohydrate diet for life to help prevent relapse of the diabetic state.

References:

1. MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Annu Rev Nutr 1984;4:521-562. 
2. Zoran DL. The carnivore connection to nutrition in cats. J Am Vet Med Assoc 2002;221:1559-1567. 
3. Eisert R. Hypercarnivory and the brain: protein requirements of cats reconsidered. J Comp Physiol B 2011;181:1-17. 
4. Elliott KF, Rand JS, Fleeman LM, et al. A diet lower in digestible carbohydrate results in lower postprandial glucose concentrations compared with a traditional canine diabetes diet and an adult maintenance diet in healthy dogs. Res Vet Sci 2011;93. 
5. Rucinsky R, Cook A, Haley S, et al. AAHA diabetes management guidelines. J Am Anim Hosp Assoc 2010;46:215-224. 
6. American Diabetes Association. Postprandial blood glucose. Diabetes Care 2001;24:775-778. 
7. Farrow H, Rand JS, Morton JM, et al. Postprandial glycemia in cats fed a moderate carbohydrate meal persists for a median of 12 hours -- female cats have higher peak glucose concentrations. J Feline Med Surg 2012;14:706-715. 
8. Farrow HA, Rand JS, Morton JM, et al. Effect of dietary carbohydrate, fat, and protein on postprandial glycemia and energy intake in cats. J Vet Intern Med 2013;27:1121-1135. 
9. Rand JS. Feline diabetes mellitus In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Fourth ed. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;133-147.
10. Rand JS. Pathogenesis of feline diabetes. Vet Clin North Am Small Anim Pract 2013;43:221-231. 
11. Zini E, Osto M, Franchini M, et al. Hyperglycaemia but not hyperlipidaemia causes beta cell dysfunction and beta cell loss in the domestic cat. Diabetologia 2009;52:336-346. 
12.  Zini E, Hafner M, Osto M, et al. Predictors of clinical remission in cats with diabetes mellitus. J Vet Intern Med 2010;24:1314-1321. 
13. Reusch CE, Hafner M, Tschuor F, et al. Diabetes remission in cats: a review. Schweiz Arch Tierheilkd 2011;153:495-500. 
14. Gottlieb S, Rand JS. Remission in cats: including predictors and risk factors. Vet Clin North Am Small Anim Pract 2013;43:245-249. 
15. Nguyen P, Leray V, Dumon H, et al. High protein intake affects lean body mass but not energy expenditure in nonobese neutered cats. J Nutr 2004;134:2084S-2086S. 
16. Keller U. Dietary proteins in obesity and in diabetes. Int J Vitam Nutr Res 2011;81:125-133. 
17. Baral RM, Little SE. Endocrine pancreatic disorders In: Little SE, ed. The Cat: Clinical Medicine and Management. St. Louis: Elsevier Saunders, 2012;547-571.
18. Bennett N, Greco DS, Peterson ME, et al. Comparison of a low carbohydrate-low fiber diet and a moderate carbohydrate-high fiber diet in the management of feline diabetes mellitus. J Feline Med Surg 2006;8:73-84. 
19. Boari A, Aste G, Rocconi F, et al. Glargine insulin and high-protein-low-carbohydrate diet in cats with diabetes mellitus. Vet Res Commun 2008;32 Suppl 1:S243-245. 
20. Zoran DL, Rand JS. The role of diet in the prevention and management of feline diabetes. Vet Clin North Am Small Anim Pract 2013;43:233-243. 
21. Roomp K, Rand J. Evaluation of detemir in diabetic cats managed with a protocol for intensive blood glucose control. J Feline Med Surg 2012;14:566-572. 

High Protein, Low Carb Diets: Key to Management of Obesity in Cats

As in humans, obesity is a major problem in cats in this country. Unfortunately, the feline obesity epidemic appears to be getting worse, rather than better (1,2). Many veterinarians and cat owners who have tried traditional feline weight loss diets (generally high fiber/low fat) have found this approach frustrating, since it usually fails to achieve significant loss of weight.

Another approach in treating and preventing feline overweight and obesity revolves around our understanding of basic feline nutritional needs and their feeding behavior (1-7). The way we feed our cats and what we feed them tend to violate all principles of "ideal" feline nutrition.

Indoor cats are commonly fed energy-dense, high-carbohydrate dry foods in a free choice manner, which provides the cat with much more energy than he or she can possible use. Outdoor cats in the wild must maintain fitness, and therefore a lean body weight, in order to successfully hunt for food. Such fitness is not required in sedentary, indoor cats, and they take advantage of the highly-palatable food that is readily available, without any undue physical effort to sustain. Free access to plentiful amounts of cat food plus little physical activity leads to overweight and obesity in cats, as in other species (5-8).

Obesity and the Composition of the Diet
One important factor that is important to consider, both in the development of 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.

The higher the concentration of carbs in the diet, the lower the intake of protein. This can result in a lower-than-needed intake of protein for maintenance and energy. We can never forget that cats are evolutionary designs to use protein and fat preferentially as energy sources (3,4). Cats have absolutely no requirement for any carbs in their diet.

Because of the metabolic requirement for cats to utilize protein as an energy source, diets with modest amounts of protein (with an average digestibility) can result in loss of muscle mass or sarcopenia (6,7,9-11). The loss of lean muscle mass leads to a lowering of the metabolic rate and can make weight gain even worse!

Traditional Weight Loss Diets Lead to Muscle Wasting
Traditional weight loss plans include feeding an energy restricted (e.g., low-fat, high-carbohydrate, high-fiber) diet. However, while these diets may result in weight loss, they do so to the detriment of lean body mass— especially in cats who use protein for energy even in the face of other energy sources in the diet.

Successful weight loss regimens requires loss of adipose tissue as well as maintenance of lean body mass (5-7). We must remember that lean body mass is the driver of basal energy metabolism (loss of lean body mass is a major contributor to weight regain as appetite is not reduced and satiety not reached).

Feeding High Protein, Low Carb Diet Best
Several recent studies have evaluated use of a high-protein, low-carbohydrate diet (protein 45% or higher) for weight loss in cats (5-7,12,13). In those studies, cats lost weight but maintained lean body mass. Importantly, high-protein, low-carbohydrate canned diets not only result in sustained weight loss in these cats, but also will help reduce the cat's urge to eat constantly. This is simply because the cats are more likely to be satiated when feeding a canned food versus a dry food with fiber.

Because dry foods must be extruded (i.e., made into a biscuit), carbohydrates are required in the cooking process. Thus, it is difficult to achieve a low-carbohydrate diet that is dry. Further, many of the available high-protein, low-carbohydrate dry foods are NOT low-calorie foods, so it is extremely easy to feed too much. Too many calories, including too many protein calories, will also cause weight gain or failure to lose weight, as well (6,7,14).

At this time, the best commercial diets for achieving a high protein, low carbohydrate profile, along with controlled calories, are canned foods. But it is important to remember that just because you are feeding a canned food, it does NOT mean that you are feeding a high-protein, low-carbohydrate diet (you must read the label), and it also doesn’t mean you are feeding a high-quality protein.

Stop Free-Choice Feeding
An important follow up point to remember about all diets is that calories count. You cannot "free choice" feed most indoor cats—even with high protein, low carb diets— because if they consume too many calories, they will become or remain obese.

The daily allotment of food should be fed in multiple small meals to mimic the cat's natural feeding strategy of hunting and catching about 10 small prey animals per day. This also increases the thermal effect of food, which increases the metabolic rate and assists in weight loss.

Calculating Calories for Weight Reduction in Cats
One key point for obesity prevention (or correction) is balancing the energy intake/energy expenditure equation. In indoor cats, where exercise is reduced by the nature of the lifestyle, energy restriction becomes paramount to obesity prevention or correction (5-7). Most indoor cats do not need more than their resting energy requirement (RER) to meet their daily nutritional requirements (this is approximately 180-200 kcal/day for a 10-11 pound cat).

Cats that are very obese will likely need to reduce their intake by 20% to 40% (or 60-80% of their RER) to lose weight (5-7). So, for a cat that is 16 pounds (7.5 kg) that should weigh 11 pounds (5 kg), it may require a reduction of calories to only 120-130 kcal/day. It is much more difficult to reduce calories using dry food rather than canned food because of the small amount of kibble that must be fed.

The key point is this: set a target calorie intake, make sure you are feeding a high protein food to protect muscle mass and prevent protein malnutrition, then weigh the cat monthly, and adjust the amount of food based on weight loss.

The Bottom Line
Energy restriction can be achieved by low-fat, high-fiber diets, but most of those diets are not high enough in protein to preserve muscle.  Such loss of muscle mass results in an unhealthy weight loss and a strong tendency to regain weight (i.e., the loss of muscle mass will always increase the likelihood of rapid regain of lost weight or failure of weight loss).

High-protein, low-carbohydrate, low-fat diets are ideal for weight loss in cats: they help preserve muscle mass while restricting energy sources that will induce fat loss. However, portion control is ultimately the key to controlling energy intake.

The easiest way to both feed a high-protein, low-carbohydrate diet while achieving portion control is to feed canned food. In cats that won’t eat canned food, there are only a few high-protein, low-fat, low-carb dry foods – but these should be selected for use in weight loss programs only when absolutely needed.

References:

1. Zoran DL. Obesity in dogs and cats: a metabolic and endocrine disorder. Veterinary Clinics of North America Small Animal Practice 2010 Mar;40:221-39
2. 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. 
3. Zoran DL. The carnivore connection to nutrition in cats. Journal of the American Veterinary Medical Association 2002;221:1559-1567. 
4. Zoran DL. The unique nutritional needs of the cat. In: Ettinger SJ, Feldman EC (eds). Textbook of Veterinary Internal Medicine, 7th edition. Saunders Elsevier, 2010;652-659. 
5. Laflamme DP. Understanding and managing obesity in dogs and cats. Veterinary Clinics of North America Small Animal Practice 2006;36:1283-1295. 
6. Zoran DL. Feline obesity: recognition and management. Compendium for Continuing Education for the Practicing Veterinarian 2009;31:284-293. 
7. 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
8. Harper EJ, Stack DM, Watson TD, et al. Effects of feeding regimens on bodyweight, composition and condition score in cats following ovariohysterectomy. J Small Anim Pract 2001;42:433-438. 
9. Hannah SS, LaFlamme DP. Effect of dietary protein on nitrogen balance and lean body mass in cats. Veterinary Clinical Nutrition 1996;3:30. 
10. Perez-Camargo G. Cat nutrition: What is new in the old? Compendium for Continuing Education for the Practicing Veterinarian 2004;26 (Suppl 2A):5-10. 
11. Wakshlag JJ. Dietary protein consumption in the healthy aging companion animal. Proceedings of the Nestlé Purina Companion Animal Nutrition Summit: Focus on Gerontology 2010;32-39.
12. 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.   
13. Nguyen P, Leray V, Dumon H, et al. High protein intake affects lean body mass but not energy expenditure in nonobese neutered cats. Journal of Nutrition 2004;134:2084S-2086S. 
14. 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.      

Diet Composition: The Key to Management of Obesity in Cats

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.

Prevention is key here. As we all know, it is much harder to take the pounds off than it is to put them on.

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.

References:

1. 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. 
2. Laflamme DP. Understanding and managing obesity in dogs and cats. Veterinary Clinics of North America Small Animal Practice 2006;36:1283-1295. 
3. Zoran DL. Obesity in dogs and cats: a metabolic and endocrine disorder. Veterinary Clinics of North America Small Animal Practice 2010;40:221-239.
4. 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. 
5. 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. 
6. 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. 
7. Kil DY, Swanson KS. Endocrinology of obesity. Veterinary Clinics of North America Small Animal Practice 2010;40:205-219. 
8. 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. 
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. 
10. 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. 
11. 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. 
12. Michel K, Scherk M. From problem to success: feline weight loss programs that work.  Journal of Feline Medicine and Surgery 2012;14:327-336. 
13. 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 
14. 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. 
15. 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.