Q.  Is this a list of foods that are recommended for cats?
A.  No, it's a reference list of the nutrient content of some commercial foods.  No recommendation is implied by the inclusion of a food on the tables.  


Q. How do you calculate the numbers on the table?
A. The numbers on the table are expressed as "percent of calories" (protein, fat, carbohydrate) or "amount per 100 calories" (fiber, phosphorus), based on as-fed information provided by the manufacturer.  For pet foods, I follow the usual assumption that protein and carbohydrate each contain 3.5 calories per gram, and fat contains 8.5 calories per gram.  You can use this Excel spreadsheet to see how the calculations are done, or read the longer explanation:

1.) Obtain "as fed" or "dry weight" values of protein, fat, carbohydrate, fiber, and phosphorus from manufacturer. Cross check: if you also have values for water and ash, the values of protein, fat, carbohydrate, fiber, ash, and water should add up to 100%.  None of them should be negative.

2.) Calculate the amount of protein, etc, in 100 grams of food by dropping the percent sign.  (Example: if a food is 9.5% protein, 100 grams of that food will contain 9.5 grams of protein.)

3.) Calculate total calories by multiplying protein by 3.5, fat by 8.5, and carbohydrate by 3.5, and summing the results.

4.) Calculate percent of calories from protein by dividing 3.5*protein by total calories.  Calculate percent of calories from fat by dividing 8.5*fat by total calories.  Calculate percent of calories from carbohydrate by dividing 3.5*carbohydrate by total calories.  Cross-check: these numbers should add up to 100%, except for rounding error.

5.) Calculate grams of fiber per 100 calories by dividing fiber by total calories and multiplying by 100.

6.) Calculate mg of phosphorus per 100 calories by dividing phosphorus by total calories and multiplying by 100,000.  (The extra 1000 is to change the units of phosphorus from grams to milligrams.)

Q.  Can I get the carbohydrate content from the numbers on the label?
A.  Not in the United States of America.  First of all, it's not listed on the label.  Second, you can't calculate it from the label because manufacturers aren't required to put average values of protein, fat, etc. on the label.  They are only required to put "guaranteed" minimum and maximum values on the label.  Sometimes these values are close to what's actually in the food, and sometimes they are quite different.  But in any event they are, by design, inaccurate.

If you live in a country which has consumer-friendly laws on what should be on pet food labels, carbohydrate content may be listed, or you may be able to calculate it by adding the values of protein, fat, water, fiber, and ash, and subtracting that sum from 100% to get "as fed" carbohydrate.  But in the USA, you're likely to get grossly inaccurate values following this method.


Q.  Why aren't the numbers on your table the same as what's on the label?
A.  Because I chose to express the numbers on a per-calorie basis, see above, which I believe makes it easier to compare foods to each other.  The values on the label are "wet weight" values -- they express the amount of each nutrient per 100 grams of food.


Q.  Can you add XXX food to your tables?
A.  Sure.  Just send me the as-fed (not "guaranteed") information, and I'll be happy to update my database.  I need the following: As-fed or dry-weight values of protein, fat, carbohydrate, water, fiber, and phosphorus, and number of calories per can of wet food or cup of dry food.  I also like to have the numbers for ash and calcium.  You may have to contact the manufacturer directly.  A customer-service-oriented manufacturer will have the information on their website.  Some manufacturers mix and match "guaranteed" values with "as fed" values, which isn't useful for these calculations.


Q.  How many calories a day should my cat eat?
A.  Short answer: Enough to maintain him or her at a healthy weight and activity level over long periods of time.  Longer answer: The common wisdom is that a cat should eat 20-30 calories per pound of cat per day, depending on its activity level, need to gain or lose weight, and personal metabolism.  However, some guardians of elderly diabetic cats have found that 20 calories per pound will cause their cat to gain weight.  If the diet contains enough protein and essential nutrients, such a cat can do well on 15-20 calories per pound.  Note that, according to the Merck veterinary manual, "healthy adult cats need ~5 g of protein of high biologic value per kg body wt/day."  This translates to 8-9 calories from protein per pound body weight per day.  From the same document, one can infer that AAFCO recommends that at least 7 calories per pound body weight should come from fat.


Q.  What should I feed my cat?
A.  I'm sorry, I can't advise you on that.  It depends on your cat's health needs, what he/she will eat, and your budget.  The general rule is to feed the most healthful diet that you can afford and that your cat will eat.  If your cat is diabetic and receiving insulin, it's also important that the food be fairly consistent from one meal to the next in terms of total calorie content, as well as protein, fat, carbohydate, and fiber content, because each of these factors will affect your cat's insulin needs.


Q.  Well, then, what did you feed your diabetic cat?
A.  I fed Binky a variety of flavors and brands in rotation, mostly depending on what he would eat, trying to keep carbohydrates below 12% of calories.  I also gave him high-protein treats from my dinner plate (as well as a bit of raw chopped London Broil as a snack).  I also tried to give him 400 IU vitamin E at least once a week, mixed in a low-fat fish-based food.  But he was not on insulin, and he did not have any complicating factors such as pancreatitis or chronic renal failure.


Q.  Someone told me that any food with less than 10% calories from carbohydrates is okay for my cat.  Is it really that easy?
A.  I wish!  No, there are other considerations when deciding what to feed your cat.  Just a few examples: Cats who are prone to get urinary crystals should get a diet with adequate water, preferably one that leads to a urinary pH of around 6.5 (mildly acidic); anecdotally, some of these cats do better when they avoid fish.  Cats who have renal insufficiency/ chronic renal failure usually need to limit their phosphorus intake, and probably should not have a diet which is very high in protein.  Again anecdotally, many cats with chronic pancreatitis avoid flare-ups if they avoid very high fat diets, and the type of fat may also make a difference for them.  Cats with heart problems may benefit from a low-sodium diet. Ingredient quality is also an important issue.  And finally, it is crucial that a diabetic cat should eat.  The healthiest food in the world doesn't do any good to a cat who refuses to eat it!


Q.  My cat needs to eat low-phosphorus foods -- how do the numbers on your table relate to the dry weight value of phosphorus?
A.  The relationship between "mg phosphorus per 100 calories" and "% phosphorus by dry weight" is not exact, as it depends on the caloric content of the food.  However, as a general rule, 1% dry weight is approximately equal to 240 mg per 100 calories, see chart.


Q.  Why are there so few foods that are low-fat and low-carbohydrate?
A.  Calories come from protein, fat, and carbohydrate; there are no other sources except alcohol, which is presumably not an option for your cat.  If you cut down on calories from one source, the other two will tend to be higher.  Because protein is the most expensive component, low-carbohydrate diets tend to be rather high in fat.  This is not necessarily a problem. Cat metabolism isn't the same as human metabolism, and a diet which is moderately high in fat will not cause weight gain if the calorie content is controlled.  However, some cats with pancreatitis, liver trouble, or high levels of lipids in their blood may need foods which are lower in fat, even if it means a diet that's higher in carbohydrate.


Q.  I've read your posts on the Feline Diabetes Message Board.  Why do you correct people when they refer to a food as having "7 carbs"?
A.  Because it's inaccurate, and, further, it may inspire other people to make the same mistake. Plus, there's no meaning to the term "carb" used in that context.  If you see a "7" in the carbohydrate column, it means that food has 7 percent of calories from carbohydrate; it does not mean it contains 7 grams of carbohydrate.  (The foods on the table are expressed in "per 100 calorie" terms so that foods may be compared to each other.)  If you'd like to calculate the grams of carbohydrates in a can (or cup) of a particular food, do the following: Multiply the calories per can (or cup) by the percent of calories from carbohydrates, and divide by 350.


Q.  Can I tell anything about the quality of the food from your tables?
A.  Only a little bit.  A food with more carbohydrates has lots of plant content, which is generally considered low quality. However, you can't tell whether the protein source is plant-based (e.g. wheat gluten, soy) or animal-based, and if the latter, whether it comes from muscle meat, organ meat, by-products, condemned meat, or what.  It's a good idea to look at the list of ingredients and do some research on the manufacturer before drawing conclusions about food quality.


Q.  Is it true that these tables are provided by cat food manufacturers?
A.  No.  The food tables are strictly a volunteer effort to help people make food choices, and I am neither funded nor encouraged by any food company; in fact, some companies are downright obstructionist when it comes to providing data.  However, it is true that the numbers are based on information provided by the manufacturers, and therefore have all the limitations of this information.  I cannot guarantee that they are accurate, or are up-to-date, or apply to any specific batch of food.  I have never said otherwise.

---