Idiopathic Diseases


Many of today’s feline diseases are treated with medications, often unsuccessfully, without ever considering that the disease may be based in something so fundamental yet mundane as the diet. In the past two decades, cats have actually decreased their longevity from into their 20’s to often now under 10 years of age. Cats, especially indoor cats that are well cared for and protected, should easily live into their 20’s as they had in the years previous to the dry cat food revolution. Certain diseases such as feline Diabetes is most likely created by man from the commercially prepared dry foods that are inundated with carbohydrates while other idiopathic (unknown cause) conditions may be directly attributed to those diets for the same reasons.

Please remember, the following information is for cats that have conditions with no known causes (idiopathic) or directly attributed to a high-carbohydrate dry diet. Other influences such as cancers, airborne allergens, etc. may also be possible causes for renal disease or urinary problems. However, a high-protein wet diet will still have positive side effects. And always consult your veterinarian when making any dietary change, particularly with diabetic cats.

Dental Disease

Consumers have been told that dry food for cats was essential for dental health because dry kibble scrapes and cleans the teeth. Yet, there is no scientific data to support this claim. Cats have sharp pointed teeth so that when they bite down on dry food only the tip of the tooth comes into contact with the kibble, breaking it or shattering it into smaller pieces. None of the hard bits actually come into contact, for abrasive purposes, with the surfaces of the cat’s teeth.

Dry food, however, leaves a starchy residue in the mouth and on the teeth. This substance sticks to teeth contributing to tooth decay and gum disease. Cats, unlike omnivores, do not have the enzyme, amylase, in their saliva which begins the breakdown of carbohydrates in the mouth. Many of the “tartar control” formulas of dry kibble contain indigestible fiber which puts a strain on the cat’s gastrointestinal tract, as well.

Raw chunked meat helps at least somewhat with dental health. Meat scraping across a cat’s teeth as they tear at it will help remove most debris. Small cats, such as our domestic cat, do not chew large bones, (such as chicken bones) as proponents of whole prey feeding purport. Small prey such as mice, rats, small birds, insects, snakes, and lizards are eaten whole or with only one or two bites and these prey generally have small bones.

The acidic aspect of meat inhibits the growth of bacteria. Cats also have an enzyme, lysozyme, in their saliva which attacks bacteria as it enters the mouth by digesting the coating on it, thereby killing it.

Stomatitis/Oral Resorptive Lesions (FORLs)

Feline stomatitis is a common, painful and life threatening problem in many cats. Cats having stomatitis often have bad breath (halitosis). They also have red and inflamed gums (gingivitis). In time the inflammation spreads from areas adjacent to teeth to areas more distant in the back of the throat. Eating and swallowing become difficult and painful for many of these cats. The causes may be disease-related such as FIV (feline immunodeficiency virus) or FCV (feline calicivirus – current vaccine protocols include FCV which will not completely prevent the disease but lessen its severity). It may also be diet-related. As stated previously, carbohydrate-laden food produces a starchy coating on the teeth and in the mouth.

Many cats with stomatitis also have tooth resorption (feline oral resorptive lesions or neck lesions). The inflamed gingiva may appear to be growing into a tooth or the tooth may appear to have a hole. These teeth are extremely painful. The main course of treatment for these cats is usually a surgical procedure involving complete dental extraction with wide excision of the inflamed mucogingival tissues.

No one has yet identified the etiology (cause) and pathogenesis (development) of FORLs. The cause may be complex. The incidence of the disease is much higher today than it was several decades ago. The advent of commercial diets, change in food texture, nutrients, synthetic diet acidification to control feline urologic syndrome and even magnesium restriction are all factors concerning nutrition that could be responsible. Proponents of a high-meat-protein, wet food diet believe that a switch to a canned or raw diet, along with medications, may provide better long term results without such drastic consequences involving surgical extractions.


When ingesting a high carbohydrate diet, the cat’s pancreas responds by releasing more insulin which may cause low blood sugar, which in turn causes the cat to feel hungry, requiring more food. Also, low meat protein diets, where the cat cannot down regulate hepatic enzymes, will cause the cat to feel hungry, also requiring it to eat more food to attain its protein requirement. Unfortunately, this cycle causes the accumulation of fat in the cat’s body which leads to obesity as calories consumed, exceeds calories burned. Cats synthesize protein and fats for energy so carbohydrates are turned to fat in the cat. Cats have limited ability to convert high loads of glucose into energy and no ability to convert sucrose and fructose.

A cat’s body should be slender and flexible with well-defined shoulders, chest, and waist. There should be a light covering of muscle and fat over the ribs, easily felt with the fingers.

•  Normal framed adult cats should weigh between 7 – 12 pounds.

•  Large framed adult cats should weigh between 12 – 18 pounds.

Most cats in the United States are now considered overweight or obese. When feeding naturally, cats would ingest a much higher meat protein profile. The cat’s body is geared for this diet and when the need is sated the hunger switch is turned off. Cats on a high carbohydrate diet, always feel hungry because they are not ingesting enough of the meat protein and fat they require to function optimally. On the high-meat-protein diet, cats often self-limit, that is, the cat’s body recognizes that the caloric protein intake has been met and the cat stops eating. Aside from obesity, this constant onslaught of carbohydrates in a protein-starved body often also produces type II diabetes for the same reasons.

Obesity leads to decreased activity, more weight gain, dry and flaky coat, and the inability to self groom which may lead to infections. Arthritis may then develop as well as depression.

The so-called “weight management” or “reduced” or “lite” foods often remove some fat and increase the fiber/carbohydrate content of the food. Cats on these diets are already starved for protein and fat and the high-fiber diets may cause constipation. Sometimes, these diets are so restricted that the cat is nutrient-starved, chronically dehydrated, and incessantly hungry.

Switching cats to a high-meat-protein, moderate-fat, low-carbohydrate grain-free canned or raw diet will allow obese or overweight cats to immediately start losing weight, even without an increase in physical activity. As weight loss progresses, the cat will in turn increase its activity level. As stated above, cats will usually self-limit on this natural type of diet. Normal weight cats will maintain their weight but tone their bodies and underweight cats will generally gain weight with increased muscle tone (lean body mass).

Monitoring weight loss is critical, particularly in overweight or obese cats. If weight loss progresses too quickly, the cat may stop eating and fat will accumulate in the liver (hepatic lipidosis) causing an emergency situation. Cats should never go more than 24 hours without eating.

Daily Caloric Intake & Monitoring Weight Loss

Daily Caloric Intake
Many pet food companies that list the caloric content of the food on the packaging or on their websites, have grossly overestimated the quantity of the food to serve to domestic cats. For many cats, feeding these suggested amounts would actually cause weight gain. The following equations will help you determine, approximately, how many calories you should feed your cat per day, this may vary by sex, sterilization, activity level, size, and lifestage (kitten, junior, mature, senior, geriatric, pregnant, and lactating).

This is a generalization so that you have a basic idea of the daily caloric intake of a domestic cat. General feeding guidelines should be adjusted up or down to maintain the ideal body weight and body condition of your cat.

12 pound cat maintaining its weight :

(13.6 calories x 12 pounds) + 70 = 233 calories (kcal) per day

Switching cats to a high-meat-protein/low-carbohydrate canned or raw diet will produce weight loss in overweight or obese cats without having to increase physical activity. However, as weight loss continues, physical activity will increase, as well, assisting in further weight loss.

16 pound cat that needs to lose weight to become 12 pounds:

12 pounds x 15 calories = 180 calories (kcal) per day minimum

Most cats will eat about 4 to 5 ounces of canned or raw food per day, based on average caloric content.

Weight Loss
If your cat is losing weight, make sure it does not lose more than 1-2% of its body weight per week. If your cat is losing too much weight too quickly, feed more food. Adding some raw or cooked chicken meat will also help raise the protein level of the food without adding too much fat. Keep this below 10% of daily caloric intake.

Calculating Percent Body Weight of a 12 pound cat:

Convert pounds to ounces first (16oz in a pound)
12 pounds x 16 ounces = 192 ounces

1% of 192 ounces
192 oz x .01 = 1.92 ounces per week weight loss

2% of 192 ounces
192 oz x .02 = 3.84 ounces per week weight loss

Your 12 pound cat should not lose more than about 1.9-3.8 ounces per week.

To help monitor weight loss, purchase an electronic baby scale to weigh your cat twice weekly in the initial stages of weight loss and a few times yearly thereafter to monitor his weight. Monitoring weight loss is important, particularly in overweight or obese cats. If weight loss progresses too quickly, your cat may stop eating, causing fat to accumulate in the liver (hepatic lipidosis) leading to an emergency situation. Cats should not go more than 24 hours without eating.

Hepatic Lipidosis (Fatty Liver Disease)

With fast weight loss or if your cat has stopped eating, it may develop hepatic lipidosis. Some cases have no known cause, however, most are associated with anorexia. When the cat is fasting (not eating) the cat’s body releases large amounts of fat that travels to the liver where it settles and clogs it so much that the liver no longer functions normally. The cat, which may have been eating minimally at this point, will want to eat even less or not at all.

Typically, the best method of treatment is the insertion of a feeding tube into your cat’s stomach by your veterinarian. You may then syringe feed your cat through this tube several times a day in your home environment for the duration of recovery. This may be necessary for approximately six weeks but has very good results. As your cat receives the desperately needed protein, it will feel better and eventually begin to eat on its own. At this point, your veterinarian will remove the feeding tube. Hepatic lipidosis usually does not recur.


As stated above, when ingesting a high carbohydrate diet, the cat’s pancreas responds by releasing more insulin which may not be sufficient to metabolize the amount of carbohydrates in its system. Hyperglycemia is indicated by high blood glucose, increased thirst and urine production, increased hunger with weight loss over time, vomiting, dehydration, and lethargy. Usually, insulin injections are required daily, however, in many cats, insulin does not seem to control the diabetes very well and the blood glucose fluctuates widely. “Prescription” diets often contain increased amounts of indigestible fiber which is supposed to prevent absorption of the sugar into the bloodstream. However, this doesn’t seem to work. The high-fiber diet often causes constipation with increased stool volume and still a high blood sugar level. Since this type of diet is not typically palatable to cats, pet food companies add flavor enhancers to entice cats to eat it. And as stated previously, the cat on a high-carbohydrate diet is starved for protein, thereby producing worse results.

Obesity is a common problem of diabetes, however, not all obese cats are diabetic and not all diabetic cats are obese. Corn is one of the main ingredients in cat food due to its availability and cheap cost in the United States. However, corn causes high blood glucose levels because it has a high glycemic index (difference by ranking carbohydrates according to their effect on blood glucose levels).

Diabetic cats that are switched to a high-meat-protein, moderate-fat, low-carbohydrate grain-free canned or raw food, will oftentimes no longer need insulin injections. For those that do still need insulin, the doses are much lower than previously required. Please work in conjunction with your veterinarian on any diet change.

Diabetic cats often need their insulin dose decreased within a day or two of beginning this type of diet. If their insulin dose is not evaluated, they could become hypoglycemic (low blood glucose ) and die.

For more information and a treatment protocol for your veterinarian to follow, please see the Diabetic Cat International site.

Urinary Tract Problems / Feline Urologic Syndrome (FUS)

A urinary tract problem, also called cystitis /FUS /FLUTD (feline lower urinary tract disorder), may present symptoms such as straining in the litter box or blood in the urine. This “disease” is very painful and must be managed with pain medications.

A cat that is straining, especially if it is not producing any urine, is in critical condition. Seek out your veterinarian immediately!

Quite often, these afflicted cats have blood in their urine. This is typically a result of the irritation (and inflammation) of the mucosal membrane in the urinary bladder from uroliths (crystals or stones) that are present.

While it is rare for a cat to actually have a urinary tract infection, it does happen. The only way to diagnose an infection is by performing a culture and sensitivity to first grow the bacteria to identify it and then to test to see which antibiotics would be effective against it. However, more often than not, the condition is idiopathic. In these cases, it is probable that a dry diet and poor quality nutrition are to blame.

Cats evolved as desert dwellers and receive most, if not all, of their water from their prey. This coupled with their low thirst drive causes them to be chronically dehydrated. Feeding dry food with its inherently low water forces the kidneys to concentrate the urine to allow maximum retention of moisture for the proper hydration of the body. This concentrated urine contains minerals such as magnesium, ammonium, and phosphorus, components of struvite crystals. Struvite crystals may then form, leading to urethral blockage and death.

When urinary tract issues became prevalent, pet food companies realized that the urine produced by these dry, carbohydrate heavy foods was alkaline, a result of carbohydrate metabolism. This is the perfect environment for the growth of struvite crystals. To combat this, the pet food industry chose to add acidifiers to the food to decrease the pH of the urine, typically DL-methionine or ammonium chloride. They also thought it prudent to reduce the amount of magnesium with the idea that if it was not available, the crystals would not form. This entire ideology is counterintuitive. Magnesium is critical to the cat for forming bones and teeth as well as other metabolic activities.

The following decade, or so, saw a decrease in struvite crystals and an increase in calcium oxalate stones. Calcium oxalate stones grow in an environment that is too acidic. The prevalence of the calcium oxalate stones is also associated with idiopathic hypercalcemia and chronic acidosis . Acidification of the diet causes, at least in some cases, the leaching of calcium from bone which is then deposited in soft tissues. Production of calcium oxalate stones may also be found in both the kidneys and bladder. Unfortunately, calcium oxalate stones require surgery to be removed.

Male cats are prone to urinary tract problems due to the small diameter of their urethras. Cats that are prescribed urinary diets usually have continued recurrences throughout their lives. Wet diets are required for any cat with urinary issues. These cats should never be fed dry food again.

Interestingly, meat protein produces slightly acidic urine (pH 6.5) which is the natural pH of cat urine and also provides the higher magnesium level required by felines.

Idiopathic Hypercalcemia

Acidifying, magnesium-restricted diets are now viewed as the possible cause of idiopathic hypercalcemia (excess total calcium and excess ionized calcium). Ironically, this disease has been increasingly diagnosed since the advent of the urinary diets. It usually affects young to middle-aged cats and is often not clinically recognized, as cats with progressed renal disease usually show a high blood calcium level. Kidney failure causes hypercalcemia and hypercalcemia causes kidney failure and it is often unknown which came first. More often, this idiopathic version is diagnosed fortuitously because of pre-surgical or pre-dental blood work since the condition has few symptoms especially in the mild to moderate forms.

DL-methionine is an acidifier commonly used in many dry cat foods and is also found in some canned versions and some cat treats. There are concerns about chronic acidification and its potentially detrimental effects on kidney function and bone development. Dietary potassium content may also be important because chronic metabolic acidosis can cause potassium depletion which can contribute to renal dysfunction. Urinary diets are typically magnesium-restricted diets, as well. Magnesium is important in binding calcium to bone.

A change to a high-fiber diet has been recommended with the idea that dietary calcium would be less available for intestinal absorption, but this typically does not change serum calcium levels in these cats for any length of time, if at all. A less acidic diet was also suggested and likewise does not seem to help.

There is evidence that a diet of high-meat-protein such as a canned or raw diet may help these cats. Adding some raw or cooked chicken meat will also help raise the protein level of the food without increasing calcium content. Only small amounts (less than 10% of your cat’s daily caloric intake) should be fed, as the meat is not properly balanced since it does not include calcium and other nutrients derived from bone and organs. For more information visit our more in depth Feline Idiopathic Hypercalcemia page.

Chronic Renal Disease (CRD)

Most cats do not present with CRD until over 70% of their kidneys are no longer functioning properly. Signs include increased thirst and urination, loss of appetite, lethargy, weight loss, muscle wasting, dull coat, and vomiting food and/or bile fluid. Acute renal disease may be treated and cured if the cause is found such as poisoning. Chronic renal disease is a terminal illness and younger and younger cats are presenting with it. Where there is no known cause such as tumor or associated illness or disease, nutrition and water intake may play key roles. There is some indication that the acidosis that occurs due to feeding acidifying diets may also be causing kidney failure with or without hypercalcemia in otherwise healthy cats.

Once again, cats evolved as desert dwellers and receive their water with their prey. When cats are diagnosed with CRD, many are immediately put on dry or canned “prescription” formulas with lower protein and phosphorus to alleviate the work the kidneys need to do to metabolize protein. However, as seen before, there is no scientific evidence to support this hypothesis. In fact, giving an obligate carnivore a protein-restricted diet will cause more muscle and organ wasting of an already debilitated body. Once again, we have an unnatural diet the cat refuses to eat which leads to more protein starvation in its weakened state. The cat is unable to down-regulate hepatic enzyme activity associated with protein metabolism even when dietary intake is low, thus the cat is particularly at risk of protein malnutrition.

Feeding an obligate carnivore what its body metabolically craves makes more sense; a high-meat-protein diet. Reduction of phosphorus may be necessary but can be done by adding phosphate binders to the food. Another method is to add chopped cooked egg white thereby increasing the protein level without increasing the phosphorus level as egg whites have little phosphorus content. One of the liver chemistry tests done to diagnose CRD is the blood urea nitrogen (BUN) test. Typically when this number is over the reference range, it is a clear sign along with other factors of kidney disease. However, BUN is a non-toxic by-product of protein metabolism. In fact, some cats on a high-meat-protein diet have BUN levels inherently higher than the laboratories’ safe range limits.

Along with diet change to a wet high-meat-protein food with or without phosphate binders and cooked egg white, medications are used for control of hypertension and other side effects of the kidney disease as well as palliative (pain control) care for the cat. Subcutaneous fluid therapy may also be indicated and can be done at home by the owner. Vitamin B complex particularly methylcobalamin a type of vitamin B 12 may help CRD cats as it improves appetite and energy levels.

Dr. Pierson can recommend a homemade diet for cats that have chronic renal disease (CRD). You may contact her via email to set up a phone consultation if you would like to make a diet that would work for your cat.

Irritable Bowel Disease

IBD is an immune-related disease featuring chronic vomiting, diarrhea, and abnormal digestive functions in the intestines and/or stomach of the cat. Food is the most obvious allergen which causes these problems. As a response, to these gastrointestinal issues, pet food manufacturers produced hypoallergenic diets, usually containing ingredients new to the cat, such as lamb and rice (fish and beef are common allergens to cats). However, the balance of the ingredients including carbohydrates, vegetables, and fruits, etc. can still produce an adverse reaction. Typically, both the dry and wet varieties of most hypoallergenic cat foods still do not provide relief. In these cases, a raw diet is the only option.

Information on this site is for general information purposes only and is provided without warranty or guarantee of any kind. This site is not intended to replace professional advice from your own veterinarian and nothing on this site is intended as a medical diagnosis or treatment. Any questions about your animal’s health or diet should be directed to your veterinarian.

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