digestive system: obesity

The Classic Comprehensive Handbook of Cat Care


Obesity (fatness) is almost always an owner-induced disease in pets caused by overfeeding and inadequate exercise. Excessive fat puts excessive stresses on your cat’s joints, heart, and lungs and often results in an inactive cat who is a poor companion. An obese cat, as you may have discovered, is more difficult to examine thoroughly than a normally fleshed one, since excess fat interferes with listening to or feeling the heartbeat, and with feeling the pulse and abdominal organs.

An obese cat is a poorer surgical risk and is more likely to develop diabetes mellitus, liver malfunction, and decreased resistance to infectious diseases. If your cat is overweight, have a veterinary examination if you want to be sure that his or her general health is good and that the obese condition is not caused by a medical problem, then start a diet. This important single step can prolong your cat’s life, as calorie restriction (providing the diet itself is nutritionally adequate) is the only dietary manipulation scientifically shown to improve longevity.

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An obese cat is 15% or more above optimum body weight. Normal cats have only a thin layer of fat between the skin and muscles covering the ribs, and each rib can be felt but not seen. They also have a defined abdomen that does not protrude far below the rib cage. Most adult cats weigh between 8 and 10 pounds; any cat weighing more than 12 pounds is likely to be obese.



Choose the weight you want your cat to reduce to. Then feed 60 to 70% of the daily caloric requirement to maintain that weight until the desired weight is reached. This could take several weeks. Never fast obese cats for weight reduction since fasting in overweight cats may trigger the onset of fatty liver disease (hepatic lipidosis), a potentially fatal condition. You can use the following table as a guide to how much commercial food will provide the proper amount of calories:

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If you make your cat’s food yourself, you will have to determine its calorie content. You can feed the calculated amount of food in as many meals as you desire each day, and experimental studies indicate that several small meals may result in greater weight loss than one or two larger ones, but remember more total food is not allowed. If your cat is accustomed to begging, dole out a portion of the daily food ration a single bite at a time. Try to distract your cat from food and increase his or her muscle tone by encouraging play with new toys.

Special low-fat, relatively high-fiber, complete and balanced diets are now commercially available for cats. Such products are reduced in calories compared to maintenance foods while still providing the proper ratio of protein to fat and all the other nutrients a cat needs. These products allow an obese cat to consume a relatively larger meal than that provided by portions of a usual maintenance diet. Although most cats can easily maintain a normal body weight when given appropriate quantities of regular commercial cat food without snacks or table scraps, weight control products are useful to cat owners who have difficulty resisting their pet’s demands for food.

Also, since many cats do not exercise regularly they will maintain their weight much more easily when fed diets lower in fat (therefore lower in calories) than the usual maintenance diets, which are designed for normally active cats. Weigh your cat weekly. A weight loss of 1% of body weight per week is sufficient. If you are following the rules set out above and your cat is not losing weight, consult your veterinarian for further help. Once your cat has reached the desired weight you can relax the rules a little to increase your cat’s calorie intake to the maintenance level for that weight.

An example: Your cat weighs 12 pounds (5.5 kg), but should weigh 9 (4.1 kg). The daily maintenance calorie requirement for this cat is about 270 calories × 60% = 162 calories to be fed while reducing. This is about 1.6 ounces (48 g) of dry food, or 2.6 ounces (78 g) of semimoist food, or about 5.4 ounces (162 g) of canned food. After the desired weight is achieved, feeding could be increased to about 2.7 ounces (81 g) of dry, or 4.3 ounces (130 g) semimoist food, or 9 ounces (270 g) of canned food.* Keep in mind that all calculations are approximate, as individual differences in metabolism affect the actual maintenance requirements significantly. Almost one cat in seven requires 20% more or less than the average maintenance calorie level to maintain a proper body weight.