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Cats Are Carnivores – Why All The Carbs?

Written by Board of Advisor member Dr. Joseph J. Wakshlag, DVM on October 31, 2017
Posted in Cat Diabetes

It is evident that the common domestic short-haired cat has become North America’s most popular pet. Unlike dogs, cats are undeniably carnivores. We know this because when cats are fed a low protein diet, they do not deregulate their liver enzymes to spare protein from becoming energy, like a dog would normally do.

This inability to spare protein metabolism to make energy gives cats an increased need for protein, which is necessary for all important structures inside and outside of cells. Researchers at the University of California Davis have spent the past 30 years solidifying this viewpoint. Every essential dietary amino acid has been studied for the diet of growing cats, giving us a very clear picture of the average cat’s protein requirements.

How Much Protein Is Necessary For A Cat?

The necessary amount of protein, at least in the author’s mind, is minimally 4 grams of high quality, highly digestible, complete protein per kilogram of body weight for a cat with normal body condition.  At the minimum, a 5 kg cat requires 20 grams of protein, which equates to 80 kilocalories of the total 200 kilocalories required for a cat’s daily intake.

This represents about 35-40 percent of the metabolizable energy for a typical indoor cat. The rest of the energy in the diet must come from somewhere else.  This is where fats and carbohydrates come in to account for the remaining calories in the diet.  Once the protein and amino acid requirements have been met, we can use these other substrates to make up the needed difference in calories, if we so choose.

Making Up For Lost Energy

Critics of commercial diets often claim that this energy should come from protein and fat and that there is no place for carbohydrates in a cat’s dietary plan.  There might be some truth to this theory. Many people have adopted these feeding practices in an attempt to eliminate carbohydrates from the diet plan, particularly because the aforementioned critics have bastardized the evidence in order to suggest that dry, kibble-based pet foods are primarily responsible for the obesity epidemic as well as the development of diabetes in cats.

When one delves into the literature base regarding carbohydrates and cats, it is evident that cats do absorb carbohydrates differently than humans and dogs. Compared to humans and dogs, the absorption of carbohydrates in cats often occurs over a longer period of time. The ability to absorb and convert fructose to glucose is problematic in cats, therefore high fructose corn syrup should be avoided.

Still, the question remains: Can cats metabolize and utilize the starches that we find in many of our commercial foods?  The answer is absolutely!  Cats do have some limitations regarding metabolism, however, since they lack salivary amylase (an enzyme that starts digesting starches in our saliva), in addition to inducible glucokinase, which limits the liver’s ability to process high levels of starch.  Fat and protein in cat foods typically account for over 60% of dietary energy, leaving about 40% of the energy, or around 20 grams of carbohydrate per day, which can be easily absorbed and processed by the typical 5 kg cat.

Carbohydrates VS Obesity And Diabetes

Let’s visit this widespread claim: Do higher levels of carbohydrates really lead to obesity, poor blood glucose control or diabetes? The reality is that when you examine the obesity epidemic, the first thing that pops up as a risk factor is the fat content of the diet. Fat has 9 kilocalories per gram, while protein and carbs only have 4 kilocalories per gram. As a result, higher fat diets have been shown to contribute to obesity in free choice fed cats when compared to higher carbohydrate diets. The primary factor is the selected kilocalorie content of the kibble, which demonstrates that portion control in cats is as important as it is in people.

Free choice feeding just doesn’t work. The typical 5 kg cat will eat approximately 50 grams of food per day, which will be approximately 40% protein, 16% fat, and 28% carbohydrate (the remainder of the kibble is about 4% fiber, 6% ash and 6% water).  This equates to around 20 grams of protein, 8 grams of fat and 14 grams of carbohydrate; well within what is considered acceptable – even for a carnivorous metabolism. Another aspect of this issue that is not discussed is that carbohydrates are needed for the cohesiveness of  an extruded kibble. Without starch, kibble would fall apart, so at least a somewhat decent amount (15-20% of the as fed amount) is required in the typical manufacturing process.

Lastly, do these carbohydrates lead to diabetes? There have been two relatively large epidemiological studies examining this as a risk factor along with a host of others. The two things most frequently associated with developing diabetes are an inactive, indoor living lifestyle and obesity. In the end, the overfeeding of kibble will lead to obesity – the leading risk factor for diabetes.  Equally important is the sedentary lifestyle that our indoor cats lead. Good cat ownership suggests allowing limited outdoor activity or daily exercise for your indoor cat. This is what we expect for healthy human lifestyle choices.  It has been well documented that once cats become obese, hormone response and blood sugar deregulation follow, making them insulin resistant. Cats display many of the same hormonal changes and inflammatory profiles as obese humans. We are not all that different from our cats.

It’s All About Portion Control

The importance of portion control creates the debate between canned food versus kibble. 50 grams of kibble is less than ½ cup of dry food.  A typical 6 ounce can of food contains140-200 kilocalories, so it’s easy to see that if we feed a single can to 1 1/3rdcan (6 to 8 ounces in volume) to equate to a typical 4 ounce serving of dry food, cats get more volume when eating canned food.  It’s also harder to overfeed canned food since the typical owner will feed ½ can twice a day – portion control at its best.

Pet owners, however, often wish to feed a mixture of both dry and canned food. When we examine Pet Wellbeing’s Holistic Cat Food, we can see that it is 44% protein is 20% fat, which which leaves very little room for carbohydrates – less than 20%, to be exact. This makes the formula one of the lowest carbohydrate dry foods on the market. With correct portion control, this could be a good solution for many cats.  Rather than scrutinize the ingredients, let’s scrutinize our feeding practices first, as this is the leading cause of obesity – the number one health problem in our cats today.

Read also: Helping Mushu, the old grumpy cat, to feel joyful and healthy after Feline Diabetes

Our Expert

Dr. Janice Huntingford
Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan

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