Obese Cats


He Ain’t Heavy, He’s My Fat Cat …Health risks of obese cats

by Dr Johan Schoeman


Hepatic lipidosis (fatty liver)

As far as our companion animals are concerned, the cat is the only one afflicted by this quite life-threatening disorder. Obese cats are particularly prone to “fatty liver”.

What Is Fatty Liver Disorder?

When a pet cat undergoes a period of starvation, either inadvertently due to being locked up without food, or through anorexia during disease states – the liver is the organ that has to ensure that enough glucose is mobilised for survival. This process of survival in the face of inadequate food intake is actually rather complex. There are many pathways in the body by which glucose can be manufactured. One of these is the breakdown of body fat to fatty acids and then to glucose. In normal cats, the liver is able to cope with the moderate amounts of broken down fat presented to it. In obese cats, however, the fat overloads the liver.The fat then accumulates within the cells of the liver, thereby impairing their function and leading to death due to complications of liver failure.

What Causes Fatty Liver?

Cats with diabetes mellitus are prone to this disorder. Drugs like tetracyclines (a certain type of antibiotic) have also been implicated. As already mentioned above, anorexia and malnutrition are major causes.Obesity is nearly always present before the onset of fatty liver. Although more difficult to prove, “stress” is believed to play a role in triggering the syndrome. Specific examples of stress in cats vary from a diet change to a less preferred food, a change in the environment such as introducing another cat into the household, or an infection caused by a bite wound.

Is Fatty Liver Common?

It is the most common liver disease recognised in cats in the USA, a country where a cat can easily weigh up to 15 kg! (This is probably because it is consuming the same vast amount of food as its owner is!) In South Africa, where obesity in people is fast reaching epidemic proportions, we can expect to see the cat population following suit. As vets we predict the increasing recognition of this disease in the near future. It is therefore imperative that clients are warned against the risk of obesity in their cats.

What Treatment Options Are Available?

Treatment revolves around providing the patient with adequate caloric intake. The vet will normally feed the cat through a tube placed through the nose into the oesophagus. This enables the liver to be provided with enough fuel to work away those fatty acids, thereby ridding itself of the excess fat. The prognosis is unfortunately poor unless the condition is caught very early and treated quite aggressively.

Struvite Bladder Stones

Why Do Bladder Stones Develop In Cats?

Bladder stones of various mineral compositions can form in the bladders of cats. The ones composed of magnesium, ammonium and phosphate – so-called “struvite” stones, are still the most common in South Africa. Inactivity, urine retention and excessive food and mineral consumption are frequently cited amongst the many risk factors associated with the formation of bladder stones in cats. These factors are all associated with, or worsened by obesity.

What Are The Symptoms?

These patients will initially void urine in inappropriate or strange places like the bathtub or the kitchen sink. They show obvious distress when voiding, may stand in the crouched position for a long time and may even cry out whilst attempting to void. The urine becomes blood-tinged with time and when the stones enter the urethra, urine flow becomes completely blocked. When this happens your cat can become desperately ill. The inability to pass urine leads to the inevitable build-up of waste products within the blood stream. An important electrolyte that is retained is potassium. Its retention has dire consequences for the heart, whose delicate electrical conduction system depends on normal concentrations of electrolytes such as sodium and potassium. When potassium concentrations are very high, the heart beats slower and slower and eventually stops.

What Can Be Done To Prevent This Condition?

Appropriate dietary management regimes will correct obesity and maintain optimal body weight. This is very important in preventing this distressing condition.

How Are Struvite Bladder Stones Treated?

A specific diet can be prescribed by your vet to dissolve the stones. If the stones are too big, they would have to be surgically removed. Specific dietary management to prevent the recurrence of the stones forms the long-term treatment of this condition.

Diabetes Mellitus

How Does Diabetes Work In Cats?

Two types of diabetes mellitus exist in cats. In both there is a deficiency of the hormone, insulin, which is produced by the pancreas. Insulin is there to lower the blood glucose and keep it within the normal range. As is the case in some humans, certain pets are genetically predisposed to diabetes, and the pancreas ceases to produce insulin. This is Diabetes Mellitus Type I, but it will not be discussed any further in this article. In overweight cats, the receptors to which insulin has to bind within the body are becoming non-functional due to interference by the excessive fat deposition. This means that the body needs to produce more and more insulin to have the desired effect on blood glucose and to overcome this “receptor defect”. This, in turn, leads to the pancreas having to work harder and harder in producing more insulin. Eventually the pancreas becomes exhausted – no more insulin is produced and your cat becomes diabetic. This is called Diabetes Mellitus Type II and is akin to the same disease in humans, also caused by obesity and dietary indiscretion.

What Are The Symptoms To Be On The Lookout For?

Firstly there is an increase in the cat’s appetite. This happens because, although there is an excessive concentration of glucose within the cat’s blood, it cannot reach the cells due to the defect in the action of insulin. The body is therefore literally “starving in the face of plenty”. This lack of glucose within the cells is interpreted by the body as a need for more food and glucose and therefore causes the appetite to increase more and more. Secondly, the excessive concentration of glucose has a further very detrimental effect. This high concentration of glucose has to be filtered through the kidneys, where it exceeds the kidneys’ capacity to reabsorb it back again. Large amounts of glucose thus end up in the urine, pulling body water with it as it traverses through the little tubules of the kidneys. This results in the formation of large amounts of urine, which, in turn, requires the cat to consume large quantities of water in order to prevent it from dehydrating and dying. Have you ever thought what happens to a cat like this that gets inadvertently locked up in the garage over the weekend?

What Can Be Done To Prevent This Disease?

The good news is that this form of diabetes mellitus, caused by interference of receptor function, can be completely prevented by keeping your cat in optimal body condition and preventing obesity.

How Is Diabetes Mellitus Treated?

A pet diagnosed with diabetes mellitus has to be stabilized by a vet and the correct amount of daily insulin treatment ascertained. The owner of such a cat will henceforth have to give their pet a daily injection of insulin, using a very fine needle and depositing the drug just under the skin of the animal. Regular urine and blood glucose analysis will have to be performed. This is in order to check the glucose concentration in the urine to see whether the insulin dose is still sufficient. Your pet will have to go to the vet for regular check-ups.

Orthopaedic problems

Why Do Fat Cats Have Orthopaedic Problems?

This is a well-known sequel of human obesity. The joints in the body have been designed to function optimally when bearing normal weight. An increase in body weight puts excessive strain on all the joints. The decrease in muscle tone that inevitably accompanies obesity – obese animals exercise less – worsens the problem further.

What Are The Resulting Diseases And What Should We Look Out For?


Typically a cat may develop arthritis of the shoulder and hip joints.  Initial signs will vary from stiffness when rising in the morning, to obvious limping. When manipulating these joints the cats often show pain. One can often detect a crunching feel under one’s hand when moving the joint. These clinical signs worsen over time, as the cartilage deteriorates and gets replaced by bone.

What Can Be Done To Ease Symptoms?

Treatment revolves around weight loss and anti-inflammatory drugs. Your pet will be put on an appropriate diet and dietary supplements. Anti-inflammatory drugs will alleviate the pain, but have many side-effects if used over prolonged periods.  To prevent your cat from having to use crutches or a wheelchair to get around, the best course of action is to keep him a lean, mean hunting machine.

Heart Disease

Why Does Being Overweight Worsen Heart Disease In Cats?

Obese patients have more tissues that have to be supplied with blood (vets call it blood volume expansion) and the heart sees this as more work. The heart therefore has to increase its output. This has the inevitable effect of increasing the beats per minute and results in higher blood pressure. Higher blood pressure is well known for placing excessive strain on the heart. The walls of the pumping chambers increase in thickness, leading to a relative oxygen deficit within the muscle cells of these chambers.

What Happens If My Cat Has A Pre-existing Heart Condition?

All these changes in the heart described above, parallels the changes seen in animals with primary heart disease. This suggests that obesity may therefore have adverse effects in patients with pre-existing heart disease. So letting your elderly cat with heart disease get fat will worsen the condition and hasten death.

What Are The Symptoms Of Cardiovascular Disease?

Difficult breathing, coughing, exercise intolerance, distended neck veins and fluid accumulation in the abdomen may all be symptomatic of cardiovascular disease. Your vet will have to do a full clinical workup, including blood tests, ECG and echocardiography to diagnose the type and extent of the disease.

What Can Be Cone For These Patients?

All obese patients with signs of cardiovascular disease should undergo dietary management with a calorie-restricted food to achieve ideal body weight. Regular exercise appropriate for the age and disease should be encouraged.  Heart disease is treated with specific drugs, including diuretics and drugs to reduce blood pressure.

Cushing’s disease

What Is Cushing’s Disease?

This disease is caused by a growth in either the brain or the adrenal gland of a cat. The syndrome (although rare) is increasingly being recognised in cats all over the world.

What Are The Clinical Signs?

Any overweight cat, with a pot-bellied appearance and a history of increased appetite, water intake and urination should be evaluated; not only for diabetes mellitus, but also for hyperadrenocorticism (Cushing’s disease). The skin is thin and stays folded when pinched. You may notice comedones (hair follicles plugged with black wax) on the hairless skin of the belly. The coat is often dull and hair loss is common.

How Is This Disease Treated?

Surgery is indicated in the rare event where the disease is localised to the adrenal gland. When the growth is in the brain, vets would normally treat with drugs, although surgical removal of these brain masses is gaining favour and is already regularly performed in countries like the Netherlands. If surgery is not indicated, the cat is treated with a drug that has to be given daily, for the rest of your cat’s life.


©Pet’s Health

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