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Feline obesity: Dietary therapy and beyond (Proceedings)


It has been estimated that at 25 to 33% of cats are either overweight or grossly obese, with the highest rates seen in middle-aged cats. Yet the 2003 AAHA Compliance Study (The Path to High-Quality Care) found that veterinarians are significantly under diagnosing feline obesity. Owners also may not recognize when their cat is overweight, nor be aware of the associated health risks. Obesity should be the easiest disorder to diagnose, but it is also one of the hardest to treat.

It has been estimated that at 25 to 33% of cats are either overweight or grossly obese, with the highest rates seen in middle-aged cats. Yet the 2003 AAHA Compliance Study (The Path to High-Quality Care) found that veterinarians are significantly under diagnosing feline obesity. Owners also may not recognize when their cat is overweight, nor be aware of the associated health risks. Obesity should be the easiest disorder to diagnose, but it is also one of the hardest to treat.

Obesity is a multifactorial problem with many influences. Endogenous factors include age, gender, reproductive status, and possibly genetics. Exogenous factors include exercise, type of diet (including palatability) and caloric intake, frequency of meals, environment and lifestyle. In recent years, research has focused on the role of adipose tissue in the process of obesity. Adipose tissue is an endocrine organ, secreting many proteins, hormones and cytokines, such as leptin. More research is needed in cats to define the role of adipose tissue in both health and obesity.1

A link between gonadectomy and obesity in the cat is well known. Research has shown that altered male cats require 28% fewer calories than do intact male cats, and altered female cats require 33% fewer calories than do intact female cats.2 Free access to food after gonadectomy is likely to result in excess weight gain. Remember to counsel cat owners at the time of gonadectomy about the need to adjust food intake in the months after altering. It is much easier to prevent obesity than to treat it!

In a recent study of 385 urban cats in France, 19% were found to be overweight and 7.8% to be obese.3 Similar to other studies, male gender, neutered reproductive status, and underestimation of the cat's body condition by the owner were identified as risk factors for being overweight. In contrast to other studies, confinement and living with no other animal did not appear to be significant as risk factors. Pedigreed cats and especially longhair cats were associated with a lower risk for obesity.

Cats reach their adult weight by about 1 year of age. Certain large pedigreed breeds, such as the Maine Coon, may take up to 2 years to reach mature adult size. Looking back in a patient's medical record for the weight at about 1 year of age is one way to help estimate ideal body weight.

Cats are considered overweight when they are 10% above optimal body weight, and obese when they are 20% or more above optimal weight. For many of our feline patients, control of obesity is a life-long issue. Weigh your feline patients at every visit and record the body condition score (BCS), using a chart such as the Purina 9-point Body Condition System. Cats are considered obese at a BCS of 6.3 or greater on a 9-point scale (3.5 or greater on a 5-point scale). Another excellent system is the Waltham Feline Body Mass Index, which provides a simple method for measurement of body fat.4 Quantifying obesity is the first step to help both you and the owner recognize the problem. If an increase in weight has occurred since the last visit, calculate the percentage weight gain. Owners may be more able to appreciate the significance of weight gain when it is expressed as a percentage, and also when trends are tracked over time on a graph or chart.

Substantial health risks are associated with excess weight gain in cats. Obesity in cats is known to be associated with diabetes mellitus, hepatic lipidosis, lameness, nonallergic skin disease and other health problems.5 It is important that both owner and veterinarian recognize that obesity is the most common nutritional disorder in feline medicine and that it has serious consequences.

There are four components to a successful weight loss program for cats:

     • Dietary change

     • Environmental modification, including increased exercise

     • Client education and compliance

     • Support and follow-up from veterinarian and staff

Before instituting a weight loss program, perform a thorough physical examination and obtain a minimum diagnostic database (chemistry panel, CBC, urinalysis) for the patient in order to rule out any concurrent diseases. Ask the owner to keep a food diary for 1-2 weeks before the new feeding regime starts. You will need information such as who feeds the cat, how much and how often; what food is fed, including treats, table food, prey from hunting, and any food or treats from neighbors. Collecting the information will help make owners aware of the role they play in the cat's obesity. For the cat to lose weight successfully, behavioral change must occur in the owner and family members.

Determine the cat's ideal body weight and use it to calculate the daily calorie requirement for maintenance of that weight. Most cats need 40-50 kcal/kg/day (use the lower end for inactive cats) for weight maintenance. The amount of calories fed will need to be about 70% of that amount to induce weight loss. However, using the food diary supplied by the client, you will also need to calculate the cat's current daily calorie intake. Some cats will already be consuming the target amount and yet fail to lose weight. For these patients, reduce intake to 80% of their current daily calories.

Advances in treating and preventing feline obesity have revolved around our better understanding of feline nutritional needs and feeding behavior.6-8 The role of convenient, palatable carbohydrate-rich, energy-dense diets as a contributing cause of feline obesity has been well established. Indoor cats fed energy-dense, high carbohydrate dry foods ad lib are provided with more energy than they can possibly use. Hunting cats must maintain fitness and an ideal body weight. They are able to self-regulate their energy intake. However, cats that do not need to hunt may lose the ability to self-regulate energy intake. They will take advantage of readily available, palatable food. Free access to food plus reduced physical activity easily leads to obesity.9

Food palatability is promoted in the marketplace and may drive consumers' choices at the expense of other important nutritional considerations. Owners have become accustomed to use food and treats to enhance the bond with their pet. In addition, many owners are not aware of just how little food is required to maintain the weight of a 10 lb (4.5 kg) cat.

Many veterinarians and cat owners have found the use of traditional high fiber/low fat weight loss diets frustrating. High fiber diets limit intake by their sheer bulk, and may fail to address the fact that cats need sufficient protein intake to lose weight. Energy restricted diets may result in weight loss, but often at the expense of lean body mass. Maintenance of lean body mass is critical to successful weight loss as lean body mass is the major determinant of basal energy metabolism.

Cats are obligate carnivores and their natural diet – small prey species – are high in protein and fat, yet contain little carbohydrate. Cats are evolutionarily adapted to use protein and fat preferentially as energy sources. For example, cats lack salivary amylase and have low activities of intestinal and pancreatic amylase compared to omnivores. Adult cats require 2 to 3 times more protein in their diet than adults of omnivorous species. An adult cat requires 3-4 grams of protein/kg/day. Cats can certainly utilize carbohydrates as an energy source, but they have a limited ability to spare protein utilization by replacing it with carbohydrate.

Cats on high protein, low fat, low carbohydrate diets can lose weight and yet maintain lean body mass.10 Commercial diets are now available from most leading pet food manufacturers with high protein/low carbohydrate formulations designed for weight management. Commercial weight loss diets have nutrient content adjusted to the caloric density of the food to avoid deficiencies. Canned formulations are less calorically dense and have lower carbohydrate levels than dry formulations. Research also supports the use of L-carnitine at 250-500 mg/cat/day to increase lean muscle mass and enhance fat utilization and weight loss.11

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 metabolic rate and assists in weight loss. Meals can be hidden around the house in various locations, or an automated pet feeder can be used.

A multi-cat household presents special challenges. One approach is to feed all the cats in the home the same high protein, low fat, low carbohydrate diet. Other options are to place food for the thinner cats in places that the obese cat cannot access, such as high locations or behind partly closed doors. An electronic or infrared cat door can also be used to make a home-made feeding station that allows only the cat wearing the key to access the food.

Part of the client education plan should be a discussion of the risks of anorexia associated with refusal to eat a new food and the potential for the development of hepatic lipidosis. It is difficult to induce hepatic lipidosis in cats that are still eating, even if they are eating only 25-45% of their normal intake. Complete anorexia is the most important risk factor and clients should be made aware that fasting due to refusal of a new diet can be dangerous.

Include in your weight management plan suggestions for improving exercise through environmental enrichment. Food puzzles or balls are a great way to provide a more stimulating environment and encourage energy expenditure. Regular play time not only helps burn calories but the interaction can also be used in place of a food treat. Owners readily assume that when a cat approaches them it is due to hunger, when it may be a request for attention and interaction. For more information on environmental enrichment for indoor cats, see the website of the Ohio State University College of Veterinary Medicine's Indoor Cat Initiative (http://vet.osu.edu/indoorcat.htm).

A follow-up phone call should be scheduled within 2 weeks of the start of a weight management program, and the call can be made by a designated staff person. Regular re-evaluations should be scheduled to monitor progress, troubleshoot, and make adjustments to the feeding program. Be aware that the amount of food may need to be adjusted several times, especially since cats tend to lose weight well at the outset, but then plateau. Initially, re-evaluate the patient every 2 weeks, then every 4 weeks as the patient makes progress. If weight loss does not occur within one month, reduce the amount fed by 10-15% until the cat starts to lose weight. A safe rate of weight loss would be 1-2% of initial body weight/week or 4-8%/month. Many obese cats will require 12 months or longer for safe weight loss.

Be sure to let owners know that patience and commitment will increase the chances of success. Many owners find the learned hunger behaviors (e.g., vocalizing, owner-seeking) of their cat increase in frequency and intensity once a diet plan is in place, and some are unable to cope with this.12 One study found that pre-weighed portions of food were better accepted than having the owner measure food daily with a cup.12 Once the target body weight has been reached, the food intake should be adjusted to maintain that weight. It is important that a relapse to old habits involving uncontrolled feeding, treats, and lack of exercise does not occur. Owners must understand that portion control will be necessary long-term lest the ground gained be lost in a very short period of time.

Celebrate the successes achieved by the combined teamwork of veterinarian, clinic staff and owner when a cat reaches its goal of optimal body weight. Be creative in your methods, such as a clinic display showing "before" and "after" photos, awarding certificates of achievement or discount coupons and gift certificates for products and services.

Top 10 Excuses Clients Give for Not Managing a Pet's Weight

(NAVC Clinician's Brief, Jan. 2007)

1. No one outlined a weight loss program before: "I was told she should lose weight, but I don't know what to do."

2. Metabolism changes: "But I don't feed him any differently than before."

3. Unable to exercise pet: "I just don't have the time to walk her."

4. Feeding is a bonding experience: "But we look forward to treat time."

5. Other people feed pet: "When I'm at work, my mom overfeeds him."

6. Previous weight loss plan failure: "She doesn't like the diet food and nothing seems to work."

7. Pet appears hungry: "But I feel like I'm starving him and he's always begging."

8. Multiple-pet household: "She eats her brother's food. What can I do?"

9. Do not see benefit of weight loss: "So what's a little extra weight? I love him the way he is."

10. Do not view pet as overweight: "She looks okay to me."


1. 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.

2. Root MV, Johnston SD, Olson PN. Effect of prepuberal and postpuberal gonadectomy on heat production measured by indirect calorimetry in male and female domestic cats. Am J Vet Res 1996;57:371-374.

3. Colliard L, Paragon B-M, Lemuet B, et al. Prevalence and risk factors of obesity in an urban population of healthy cats. J Feline Med Surg 2009;11:135-140.

4. Hawthorne A, Butterwick R. The feline body mass index - a simple measure of body fat content in cats. Waltham Focus 2000;10:32-33.

5. Scarlett JM, Donoghue S. Associations between body condition and disease in cats. J Am Vet Med Assoc 1998;212:1725-1731.

6. Zoran D. The carnivore connection to nutrition in cats. J Amer Vet Med Assoc 2002;221:1559-1567.

7. Zoran DL. Feline obesity: clinical recognition and management. Comp Contin Educ Vet 2009;31:284-293.

8. Laflamme DP. Understanding and managing obesity in dogs and cats. Vet Clin North Am Small Anim Pract 2006;36:1283-1295, vii.

9. 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.

10. Vasconcellos RS, Borges NC, Goncalves KN, et al. Protein intake during weight loss influences the energy required for weight loss and maintenance in cats. J Nutr 2009;139:855-860.

11. Center SA, Harte J, Watrous D, et al. The clinical and metabolic effects of rapid weight loss in obese pet cats and the influence of supplemental oral L-carnitine. J Vet Intern Med 2000;14:598-608.

12. Bissot T, Servet E, Vidal S, et al. Novel dietary strategies can improve the outcome of weight loss programmes in obese client-owned cats. J Feline Med Surg 2010;12:104-112.

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