Obesity in Cats and Dogs

By Nancy Otten, Animal Health Technologist

How can I tell if my cat or dog is obese?

30% of cats and dogs are clinically obese.  A dog or cat is obese when they are over 15% of their ideal body weight.  What does that look like?  In a cat, that means that their ribs are not easily palpated (examined by touch) or cannot be palpated at all.  Their abdominal fat pad (the pad of fat found between their back legs) is quite extensive.  If they are grossly obese they will also have fat pads over their lower back, on their limbs, and on their face.  If you looked at an obese cat from above you would not see a waist.  An obese cat in silhouette has a distended and hanging belly.

Obesity in a dog has similar characteristics.  These dogs have heavy fat cover over their ribs making them difficult or impossible to palpate.  They have heavy fat deposits over their lower back and at the base of their tail.  Grossly obese dogs also have massive fat deposits over their neck, thorax, along their spine, at the base of their tail, and on their limbs.  If you looked at an obese dog from above, you would not see a waist and their silhouette would expose a bulging belly.   

Why is obesity dangerous?

Obesity can cause diabetes, cardiovascular disease, respiratory disease, and joint problems.  It also makes the animal prone to heatstroke, gastrointestinal disease, liver disease, skin problems, and reproductive disorders.

How do I get my pet down to a proper weight?

Just like with people who want to lose weight, two things must happen.  The amount of calories consumed must decrease and the amount of exercise done must increase.  It will be impossible for your pet to lose weight if you free feed them.  Free feeding is when you fill the bowl to the brim and let them eat whenever they want to.  Some animals will do fine when free feeding and will only eat what they need.  However, other animals will overindulge to the point where they develop a weight problem.  It is necessary to figure out how much food your pet needs per day, divide that volume into two meals spaced approximately 12 hours apart, and be very strict about it.

How do I determine how much food to feed?

If you already feed your pet twice per day, it might be as simple as slightly decreasing the amount of food that they get with every meal.  If your pet is mildly overweight, decrease the volume by 10 to 15%.  If your pet is obese, decrease the volume by 25%.  Don’t expect instant results.  It may take several months before your pet reaches its ideal weight.  If you free feed, you can do two things.  You can read the pet food bag to get an idea of how much food they recommend that you feed your pet.  If your pet still doesn’t seem to be losing weight, you may have to reduce the volume even more.  The second way that you can determine how much to feed your pet is a bit more scientific and requires some math.  Get out your calculators!  The first bit of information that you will need is the number of kilocalories in a cup of your pet’s food.  You will not find this information on the bag of food so you will need to call the manufacturer to get this information.  Record this number.  The next thing that you will need is your pet’s weight in kilograms.  Record this too.  Your first calculation is your pet’s resting energy requirement (RER.)  To find that you need to multiply your pet’s weight times 30 and then add 70 (weight x 30 + 70.)  Now you need to find your pet’s maintenance energy requirement (MER.)   In order to achieve weight loss in cats, you find the MER by multiplying the RER by 0.8.  In order to achieve weight loss in dogs, you find the MER by multiplying the RER by 1.0 (for dogs, MER=RER.)  To find out the volume of food required per day you take your pet’s MER and divide it by the number of kilocalories in a cup of your pet’s food.  That will tell you how many cups to feed.  Divide this number by 2 to get the volume per meal.  Whew!

Here’s an example:

Your cat’s food has 282 kcal per cup.  Your cat weighs 6 kg (just over 13 pounds!) 

RER= (6 x 30) + 70 = 250 kcal

MER= RER x 0.8 = 250 x 0.8 = 200

Volume of food = 200 divided by 282 = 0.7 cups

0.7 cups is just under ¾ cups so you would feed just over ¼ cup twice per day to achieve weight loss.   

It should be noted that you must weigh your pet frequently (every three weeks) and adjust the RER and MER accordingly. 

How do I find the right food to feed?

You should consider changing over to a weight control diet unless your pet is a juvenile or a geriatric.  Weight control diets have less kilocalories per cup so you can feed a larger volume than regular food.  It is higher in indigestible fibre which will make your pet feel full after eating but they won’t be consuming lots of calories.  Kittens and puppies must be fed a growth formula because they have specific requirements that only growth formula can provide.  Older cats and dogs should be fed a geriatric formula which satisfies their specific needs.  Any change in diet, or weight loss program, should be made under your veterinarian’s supervision.  It should be noted that, generally, the cheaper the pet food, the poorer quality it is.  It definitely pays to buy good quality food.

How do I increase the amount of exercise that they get?

Like people, pets can get overweight and out of shape.  It would be unwise to enter them into an intensive exercise regimen right away.  It is important to slowly increase the amount of exercise that they do.  For dogs, you might start them off with a half hour walk, slowly increase it to an hour walk, then a 20 minute run and then, before you know it, he will be able to go mountain biking with you (you on the bike, he on foot!)  Cats are a bit more difficult.  They are stubborn!  It may take some experimentation to discover what will get your cat interested it moving around a bit.  Chasing a string up and down the stairs for a couple of minutes may be a good start.  Eventually your cat will stay interested in running up and down the stairs for longer periods. 

How do I know when my pet is at its ideal weight?

A cat at its ideal weight will have a slight bit of fat over its ribs but its ribs will be easily palpated.  Its abdominal fat pad will be minimal.  When looked at from above, there will be a waist behind its ribs.  Its silhouette will show a flat stomach or a slight abdominal tuck (its abdomen will be slightly higher than its ribcage.) 

A dog at its ideal weight will have a slight bit of fat over the ribs but the ribs will be easily palpated.  When looked at from above, the dog will have a definite waist.  In silhouette, the dog’s abdomen will be tucked up higher than the ribs.

How do I keep my pet at its ideal weight?

You’ll need to increase the calories that your pet is getting to prevent further weight loss.  This is accomplished by increasing the amount of food they get with every meal.  You will need to monitor his weight closely to make sure that he doesn’t start gaining again or keeps losing weight.  If you are using the exact and scientific method:  to maintain a normal cat at a certain weight, you would need to multiply the RER by approximately 1.1 to find the amount of kilocalories he should consume in a day.  For dogs, you multiply the RER by approximately 1.5 to find the amount of kilocalories he should consume in a day.  Remember that these formulas are only guidelines.  All animals are individuals and their metabolisms may vary.  Their diets must ultimately be adjusted to their individual needs.  For example, dogs that are very active and run for hours per day will need 3 or 4 times their RER.