Westbury Animal Hospital
713.723.3666 · 4917 S. Willow Dr. Houston, Texas 77035 

Feline Obesity – Where Did We Go Wrong?

by Jenny Garb, DVM


How many times have you watched a lion pounce on a loaf of bread on a nature show? How many times have you been “honored” by your cat depositing a piece of dry kibble at your feet?  Never!  As ridiculous as these scenarios may sound they serve as a backdrop to a tremendously important topic in veterinary medicine – the feline obesity epidemic. 

When we look back at history cats and humans have coexisted for centuries.  Over the past several decades there has been a shift in the human-feline relationship as the mouse-eating barn cat has been replaced by the couch-dwelling, kibble-eating, sedentary, sexually altered cat of today.  Not only have we moved them into the safety of our homes but we have managed to extend our cats’ natural life spans significantly by vaccinating them against infectious diseases, protecting them from environmental hazards and feeding them commercially prepared feline diets.  And yet we are faced with a health crisis in the feline population that mirrors the biggest human health threat in the United States today: obesity.  It is estimated that a staggering 35-50% of indoor cats suffer from excess body weight. 

It is not news to anyone that the consequences of obesity, whether human or feline, are profoundly debilitating.  Diabetes, arthritis, lower urinary tract disease, skin diseases and liver disease are only a few of the conditions that have been associated directly with excess body fat in cats.   So why are our cats packing on the pounds?  As you will see, we have managed to remove our cats from the wild but we have not succeeded in removing the wild from our cats, particularly when addressing their nutritional needs.

Genetic predisposition, a sedentary life style, neuter status, diet and eating habits have all been identified as obesity risk factors in domestic cats.  While neutering and spaying cats is essential for population control and prevention of reproductive and cancerous diseases there is now ample evidence that hormonal changes that happen immediately after neutering and spaying cats increase their appetite and decrease their metabolic rate  - predisposing them  in their adolescence to weight gain and obesity. 

In order to understand the cat obesity epidemic one needs to understand the basic nutritional needs of felines, which have changed little over the millennia.  The ancestors of our domestic cats were desert dwellers.  Water was scarce, forcing them to adapt to obtaining the majority of their moisture from hunting and eating rodents, birds, reptiles and insects.  This adaptation explains why cats, whether domestic or wild, do not have a strong thirst drive.  Unlike humans or dogs, cats evolved as strict carnivores, dependant predominantly on animal protein to meet their nutritional needs.    In fact, cats developed unique anatomical features to fulfill these needs. Their teeth, intestines and even saliva evolved to digest animal protein. Even their enzymatic pathways were designed to use animal based proteins to fulfill their nutritional needs.    It is important to understand the implications of being a strict carnivore.  While humans and dogs, who are considered omnivores, can use plant based protein to create all of the protein building blocks (also known as amino acids) they need for survival, cats cannot use plant based protein to construct their amino acid profile.  While animal proteins have a complete amino acid profile, plant based proteins do not contain all of the amino acids required by strict carnivores. 

You may be wondering how all of this is relevant to the eating habits of our domestic cats.  Let’s start making the connection by looking at dry kibble, the most widely used form of cat food around the world.  The convenience it offers owners, its availability and ease of storage, its palatability and its balanced nutritional content have made it an attractive form of nutrition for domestic cats even though it bears no resemblance to the protein and moisture dense diet of true carnivores. The process of making dry kibble has to include carbohydrates.  Carbohydrates are inexpensive starch fillers and can consist of “grains” (corn, wheat, rice, soy) or “non-grains” (peas, legumes or potatoes).  35-50% of the calories in dry food are derived from carbohydrates while only 3-5% of the calories in an average mouse are derived from carbohydrates.  Thus, dry kibble supplies 5-10 times as much calories from carbohydrates compared to the diet of a strict carnivore.  Furthermore, while dry kibble is 7% water a mouse or a can of cat food is 78% water.    So it is not difficult to understand why indoor cats who eat predominantly dry food suffer from chronic, low level dehydration despite drinking twice as much as a cat eating canned food. Eating dry kibble impacts water intake profoundly.  So while cats on dry food do drink more they still do not drink enough.  This becomes particularly important when taking into account that one of the most common ailments of cats involves the kidneys and bladder – both highly dependent on water to “flush” them out.  It is also easy to understand why our cats are becoming obese – they are ingesting very high levels of carbohydrates which are mainly deposited as fat in their bodies. 

We have established that dry kibble can pose many health problems for cats.  However, the content of dry kibble is not solely responsible for our chubby felines.  Offering our indoor cats a bowl of dry food around the clock is the second mistake we make when feeding our cats.  For reference purposes, the calories in a single mouse are equivalent to approximately 10 dry kibbles, regardless of brand.  A quick comparison comes up with a grim picture:   while a mouse may serve as a meal for a cat there is not a cat that would be satisfied with a meal of 10 kibbles.  So it is easy to see how the risk of overfeeding goes hand-in-hand with free feeding - even small amounts of kibble can exceed energy requirements and promote weight gain.  Free feeding dry food also prevents owners from assessing their cats’ health status which can often be estimated based on food intake – particularly in multi cat households.

 So how do we help our cats lose weight?  Until kitty treadmills are invented, diet is the key to improving the health of our cats.  Reverting out indoor cats back to their primal diet of rodents and birds is clearly not an option but feeding our cats a canned diet is the second best diet option that is readily available. While sudden diet changes of any sort are not recommended, using the following strategies could be instrumental in our battle against the feline bulge.

-        Feed cats canned cat food rather than dry food - the canned diet of choice should be discussed with your primary veterinarian.  Unless advised otherwise a canned food that is high in protein, low in carbohydrates and has a moderate amount of fat would be desired.  Dry food that is labeled for weight loss may reduce weight by restricting calories but the weight loss is typically unhealthy and involves the loss of muscle, not fat.  

-        Introduce kittens to canned food from the time they are weaned.  Canned food should comprise at least 50% of an indoor cat diet.

-        Control food intake immediately after spaying or neutering:   this can be achieved by refraining from free feeding dry food while offering controlled portions of canned food.

-        Closely monitor body weight: if your cat seems to be gaining weight please approach your primary veterinarian sooner rather than later to discuss the diet changes that need to be made. 

It is safe to say that even though our cats have been domesticated their nutritional needs have not.  Canned cat food will never be able to replicate the nutritional composition of a cats’ natural prey but it is many steps closer to the most basic nutritional needs of our cats: moisture and animal based protein.



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