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Obesity: The Thick and Thin of It

The population of overweight and obese pets continues to expand in Canada and around the world. As with people, excess weight is associated with several potentially serious and even life-threatening health conditions. In this post, we explore the various causes and consequences of pets being overweight or obese, and what we can do for them.

While there are very specific definitions for overweight and obesity in people, the definitions in pets are more arbitrary. Dogs and cats are often considered overweight if their weight is >15% above ideal and are obese when weight is >30% of ideal. In veterinary medicine, body condition scores (BCS) are used to evaluate a pet’s weight. The 2 most commonly used scales are:

A 5-point scale:
We use this at St Vital Veterinary Hospital – Click to Enlarge:
Body Score Dog Chart

A 9 point scale:
Body Condition Score for Cats – Click to Enlarge:

Body Condition Score for Dogs – Click to Enlarge:

Obesity causes – luck of the draw, or?

In 2012 the Association of Pet Obesity Prevention published some pretty staggering facts: 52.5% of dogs and 58.3% of cats in the United States are overweight or obese. It is likely similar here in Canada. I know in everyday practice, many of the patients I see continue to gain weight from year to year. So how does this happen?

At Risk Breeds

Some breeds have been shown to be predisposed to obesity, particularly: Terriers – West Highland White Terriers, Scottish Terriers; Shetland sheepdogs; Hounds – Basset hounds, Dachshunds, Beagles; Spaniels – Cavalier King Charles spaniels, Cocker Spaniels; Labrador retrievers. Interestingly certain breeds, particularly sighthounds (i.e: Greyhounds, Whippets, etc)., appear to be resistant to the development of overweight and obesity. But what about cats? Several cat breeds are also over-represented with overweight and obesity, including Sphinx, Birman, Ragamuffin, Shorthairs (British, American, Exotic, Domestic), Manx and Persian.


As pets age, they are generally less active and they can lose lean body mass, which means they need less daily calories. The total daily energy needs of an average-sized 7-year-old dog may decrease by as much as 20% when compared with its needs as a young adult. If their food intake does not decrease proportionately with the decreasing energy needs, they gain weight.

Spaying & Neutering

When we spay & neuter, this results in a loss of circulating sex hormones that slow a pet’s metabolism by directly affecting the hunger center in the brain through changes in specific hormones (leptin and ghrelin).
Medications – Certain medications, especially those given chronically, can contribute to obesity in pets. For example, Corticosteroids (ie. Prednisone) used in autoimmune diseases, and allergies, can cause increased appetite leading to weight gain, increased sugar levels and abdominal fat production.


It’s not always what we eat, but how we eat. A good quality diet that suits your pets needs are ideal, but even the most calorie-restricted diet can cause weight gain if overfed. How many meals a day? What about dog cookies and table scraps? Interestingly, the cost of pet food may have an effect on body weight. One study showed obese dogs were more likely to be fed a higher volume of cheaper brand foods than premium.

Pet Owners

What is our role as pet owners? I know many owners find it difficult to say no when their pet beguiles them with “Please, I’m starving even though you just fed me 30 minutes ago, please share that microwave popcorn” or “Look how cute I am grooming myself! I know I can’t reach my bum, but please pile Temptations in front of me like the royalty I am.” Food is love (in moderation), but so are other non-calorie dense ways we can interact with our pets that keep them physically fit and mentally stimulated.

Interestingly, when people are exposed to environments with a high prevalence of overweight and obesity, they often develop inaccurate perceptions of what constitutes a healthy body shape. A recent survey study collected data from 829 dog parents through personal interviews; they were asked to subjectively evaluate their dogs’ body condition score (BCS). Additionally, both the pet parent’s body mass index (BMI) and the dog’s BCS were assessed. Obese dogs were twice as likely to have obese owners as non-obese dogs were. Furthermore, dog parent underestimation of their pet’s BCS was nearly 20 times more common in dogs that were obese than in normal or underweight dogs. Given this information, pet owner misperception of an obese dog’s BCS is a major obstacle in weight management.

Obesity consequences: You are what you eat

Fat absolutely has a vital role in the body: it helps to insulate against cold, provides a cushion against trauma, and produces hormones called adipokines that help regulate energy balance, metabolism and immune function. However, when too much fat is present, adipokines can actually contribute to a state of chronic inflammation.

Just as overweight and obesity have many possible consequences in people, so too do they have serious health implications in dogs and cats. Excessive fat impacts our pets in many ways,

Longevity: Studies have shown that pets fed a calorie-appropriate diet lived 1.8 years longer than pets fed free-choice

Hormone Diseases: Diabetes mellitus (sugar diabetes) requiring long term medication (insulin), pancreatitis (inflammation of the pancreas)

Orthopedic Conditions: increased development of arthritis from the excessive weight on the joints, soft tissue injuries like Cruciate ligament tears requiring expensive surgical repair.

Heart Disease, High Blood Pressure & Respiratory Conditions: Tracheal collapse, asthma, exacerbation of Brachycephalic Airway Syndrome. As in people, overweight and obesity can affect blood pressure. Untreated hypertension (high blood pressure) causes damage to various organs, most notably the kidneys, brain and heart.

Cancer: A limited number of scientific investigations have evaluated the correlation between overweight/obesity and cancer development. Some of the data suggest overweight and obese dogs and cats have an increased risk of developing cancer.

Combating obesity: Bootcamp?

Wow! That previous section seemed really negative you’re thinking. It’s certainly not meant to be a scare tactic, but a realistic view of what can happen with excessive weight. Even though overweight and obesity are becoming more common in our companion animals, identifying excess weight on your pet is the first step! If you think your pet is overweight, or if we identify your pet as overweight at their annual physical, don’t despair; we have successfully helped many pets achieve a healthy weight through a combination of:

Dietary modifications – a calorie-appropriate amount of an appropriate nutrient-dense food, often calculated with consistent weigh ins & adjustments,

Lifestyle changes – exercise programs, appropriate play (both indoors and outdoors), increased mental stimulation to prevent boredom eating,

Drug therapy – as a last resort.

The take away (not take-out) message about obesity…

Excess weight is an increasingly common health problem in dogs and cats here in Canada and around the world, increasing the chances of diseases and decreased quality and length of life.
Fat is a metabolically active tissue that, in excessive amounts, contributes to a stage of chronic inflammation.
Overweight and obesity are treatable, and several effective therapeutic interventions are available. A collaborative effort between pet owners and your veterinarian results in a highly effective team to achieve healthy weight loss through regular monitoring of prescribed weight loss techniques.



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