In human medicine circles, the argument about whether or not obesity is a disease or mostly a lack of self discipline on the part of over eating, under exercising people is a hot issue mostly because of political and economic problems.  The big economic issue being whether health insurance companies will be required to pay for weight loss programs if obesity is classified has a disease.

In veterinary medicine, we aren't so concerned with political and economic considerations.  In veterinary conferences, obesity is now being accepted as an endocrine disease for several good scientific reasons.

I recently went to a conference about obesity in pets that changed my understanding of the problem.  Here's how I summarize what I've learned:

Old information that's still true:  people and pets get fat mostly because they tend to over eat, under exercise, and because our diets are very calorie dense.

New information:  more and more evidence is coming in that there are medical, scientific genetic and metabolic reasons that some pets and people gain excessive weight compared to other individuals eating the same diet.  There is new information that fat patients don't respond to the hormones that effect satiety (as sense of fullness)

Somewhat new information:  the feeding recommendations required on pet foods are about 25% higher than most pets should be fed... especially if the pets have been neutered or spayed

Really important new information: adipose tissue, or fat, in thin pets and people is fairly inert BUT once fat cells grow big and multiply they become ACTIVE, hormone producing cells.  So far, 12 different enzymes and hormones have been identified.  Some of these enzymes and hormones cause inflammation.  Some increase blood pressure.  Some negatively influence insulin sensitivity and fat metabolism.  Dr Graves, endrocrinologist at the Veterinary School of Illinois calls the adipose tissue the largest endocrine organ in the body.

New information:  Adipose tissue in fat pets becomes abnormal;  lypolysis or the burning of fat for energy becomes abnormal, fat pets become less sensitive to circulating signals that limit hunger.

New information: In normal pets, adiponectin enhances insulin sensitivity, decreases free fatty acids, triglyceride and glucose levels.  Fat patients have lower levels of adiponectin than normal patients.  We don't know why, but it indicates that obesity is NOT just a matter of eating too much.

New information:  energy balance, blood pressure, insulin secretion and resistance, and glucose homeostasis are all negatively affected by adipose tissue.

Critical new information:  Leptin is a hormone that in normal pets regulates hunger and fat metabolism.  Fat patients don't respond normally to leptin.  Leptin levels are higher in fat patients but leptin seems to be ineffective at causing satiety and stimulating fat metabolism in the obese. 

Really important new information:  The cells in the intestine produce several peptides or chemicals during digestion that signal the brain to stop eating.  One of these peptides is known as Peptide yy  or PYY.  Fat patients are sensitive to this peptide just like normal patients, but fat patients don't produce normal amounts of PYY.  This is critical because if a PYY like medication could be made, we could give this peptide to fat patients to make them feel less hungry. They would help fat patients feel satiated.   Apparently this has been successful; the first and only new FDA approved has just recently (2007) been released on the market.  It's called Slentrol and is 97% effective in dogs and it works by stimulating increased PYY production by the intestinal cells.  Unfortunately, this new medication caused elevations of liver enzymes in humans and cats and has only been approved in dogs.  And for reasons I haven't been able to find out, Zoeitis (the new company name for Pfizer's animal products) is no longer offering Slentrol in the United States. (as of March 2014)

On this page:
We are discussing obesity in our section about metabolic diseases for a good reason.

It turns out that adipose tissue is the largest metabolic organ in the body and producer more hormones than any other gland.  12 hormones have been identified so far.

This page is an introduction to all the new information coming out about obesity and what you can do about it.

About other metabolic diseases
in cats and dogs.
(There is a complete directory of links at the bottom of the page)

Intro to Metabolic Diseases


Addison's Disease   

Cushing's Disease   



Heat Stroke     

Liver Disease    


Kidney Disease  

Help with interpeting lab results

Gastro-Intestinal Disease 

Fat pets live on average 1.8 years LESS than normal weight pets

We get a lot of enjoyment when we feed our pets.  But we are loving our pets to death.

About 40% of American cats and dogs are overweight.  About 10% are considered obese

Obesity is loosely defined as being 20% of more over ideal weight

Fat patients
are much  
more likely
to have:

Heart Disease
fatty liver disease
orthopedic problems
obstructive sleep apnea
glucose intolerance
Respiratory Disease
Spay Incontinence
Urinary Tract Disease
Tracheal Collapse
Anesthetic Risk

There is a genetic component to obesity.  We know that certain breeds are much more likely to be fat than other breeds.  Common breeds prone to obesity are Labradors, Cairn Terriers, Cocker Spaniels, King Charles Spaniels, and Scottish Terriers.  Dachshunds, Shelties, miniature schnauzers, beagles, and bassett hounds are also known to be more prone to obesity.

Spaying and castrating pets reduces calorie needs by about 25%

Fat tissue releases pro-inflammatory cytokines

When pets (and people) gain weight, fat cells increase in size and number.  In weight loss, the cells shrink in size but not numbers.  The only way to reduce the number of fat cells is to surgically remove them ... not presently a common procedure in veterinary medicine.

Fat cells are major hormone factories... driving appetite, activity, and metabolism.

There are chemicals made in the stomach and intestinal system that make us feel hungry and full.  This system seems to be abnormal in fat patients making obesity a disease ... not just a matter of poor will power.

One of the more important chemicals controlling our hunger is a peptide called PYY. Obese individuals have to consume more calories to stimulate PYY secretion than do non obese individuals.

Obese dogs are much more likely to get transitional cell carcinoma

Intermittent feeding... as opposed to free feeding ... helps with weight loss

Diets must contain enough high quality protein to prevent loss of lean muscle.  Muscle mass must be maintained to prevent metabolism shift.

Fat content should be low to moderate (except low fat diets should be postponed when using the new weight loss medicine Slentrol)

Low Carb diets seem to be important to weight loss in felines.

It's frustrating, but even when increased exercise and reduced calorie diets are forced on pets, many don't lose weight.  This fact is another clue that there are more factors involved and once again indicating that obesity is a disease.

Certain medications, especially steroids and phenobarbital affect weight gain.

Help your pet live a longer, happier, healthier life.  Take the effort to make some changes and get the weight off.

as a disease ...
a lot of new information
... and about a new diet that actually works
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What To Expect When You Go To The Vet
(Of course, your vet may do things differently)

Exam:  Because fat patients are more prone to diabetes, arthritis, heart disease, kidney disease, and inflammation of ears, gums, skin, anal glands, and other tissues, we will be asking questions and looking closely for these problems.

We will spend a lot of time discussing the pet's diet and exercise regimine.

And of course, we will keep a record of your pet's weight and body condition score.

Diagnostic Tests That Might Be Recommended:

Routine Blood Panel
There are 2 important reasons for getting the medical information we get from routine blood panels.

Important reason # 1:  some overweight patients are fat because of metabolic diseases such as thyroid disease, Cushing's disease, and diabetes. 

Important reason #2:  fat patients are much more likely to have diabetes, thyroid imbalances, kidney problems, infections, and liver problems than normal weight patients.  Blood work lets us know what's going on before the the patient becomes overtly miserable.

Radiographs are recommended:
Fat patients are much more likely to have heart disease and arthritic joint diseases.  Radiographs remain the best way to detect these problems in the early stages of the disease.  This is especially true for detecting feline heart disease ... a common disease that we miss during routine exams until the cat is deathly ill.

Treatment Options:

More Exercise:  My only comments here are that it's very important to your general health, your joints, and your weight to keep active.  Another comment is that if you can get your pet excited about some activity such as ball chasing, frisbee catching etc ... you might be able to transfer play rewards in substitute for food rewards.

Of course, it's hard to increase exercise if your pet also has arthritis, an injury, or your dog is so obese that exercise is dangerous.

Change your pet's feeding habits: substitute things like carrots, green beans, rice cakes, unbuttered popcorn,  cherrio's, or low calorie pet treats for high calorie pet snacks. 

Stop feeding table scraps.

Feed a little less over time.

Get serious with presciption weight loss diets made by Hill's, Royal Canin, or Purina.  These have worked in many cases with preseverance.  These diets are basically of two types; low carb, high fiber diets like Hill's R/D, and Atkin's like diets with moderate fat, high quality protein, but low carb diets such as Hill's M/D diet and Purina's OM (obesity management) diet.
Please click here to go to our page about special diets for more details.

NOTE:  We've been recommending
Hill's MD diets at our clinic because
it's really working in most of the pets
that stick with it for at least a few months. 
Most of the pet's on this diet....
if they don't get too many treats...
are losing significant weight over a
3-6 month period.  I'm impressed.

MD treats are available too.

Actually working and available for both cats and dogs
Excessive weight puts a major strain on every organ in the body.  Read the alarming list to your left.
Drugs that decrease fat absorption like the human medication Orlistat:  major side effect of uncontrollable, oily stools, GI irritation and fat soluble vitamin deficiencies are problems.  note; just to avoid a common misconception, Slentrol does not cause this problem.

Surgical Reduction of fat through liposuction or gastric surgery:  Dr Grave calls this the most successful way to lose weight.  I'm not sure why it's not commonly done in veterinary medicine.

Slentrol:  This is the name of the new FDA approved medication that helps dogs stop begging, stop being hungry all the time and more importantly seems to be safe and very effective.  You can expect your dog to lose about 1% of weight EACH WEEK starting about 1 month after starting the medication.
2014 Update: For reasons unknown to me Slentrol is being removed from the U.S. market.