Pet Health
Diseases & Conditions Contributing to
Obesity in Dogs

Holly Frisby, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc.

Dogs may become overweight for many reasons.
Whether the obesity is due to simple overfeeding
or a result of a disease process, the bottom line is
the same: the dog is taking in more calories than
he is using. Regardless of the cause of obesity, the owner is ultimately responsible for regulating
the dog's caloric intake and use, and in seeking veterinary assistance in maintaining the dog at
the optimal weight. Humans are the main cause of obesity in dogs.

Some of the more common diseases and conditions which can contribute to obesity in the dog
are discussed below.

Food type, availability, and palatability:  
Some dogs will only eat what they need and do fine if
their food is available free choice (available at all times).
Others will eat as much as is available and then look for
more. Some dogs are finicky and others will eat just about
anything. So the amount and type of food that is fed and t
he eating tendencies of the dog can determine how likely
it is a dog will become overweight.

The type of food fed has a direct bearing on the tendency
of a dog to become overweight. Table scraps, treats, even
premium high-energy dog foods can contribute to obesity. A 7-year-old labrador whose main
occupation is laying in front of the hearth does not need a high-energy dog food, whereas his
brother who is a field dog and lives in an outside kennel has high energy needs and a premium
high energy food is in order.

Activity level:
Activity level plays a major role in determining the caloric needs of a dog and thus his tendency
to become overweight. An active dog will use more calories. In addition, an active dog's mental
state may make him less likely to eat more because of boredom or stress.

Neutering and spaying:
Neutering and spaying dogs lowers their
metabolic rate such that they require fewer
calories than intact dogs. In addition to changes
in metabolism, androgens and estrogens (male
and female sex hormones, respectively) stimulate roaming
behavior and general physical activity. Estrogen, in addition, has the effect of decreasing appetite.
Spayed animals never have the extra energy demands of pregnancy or raising a litter.

Since their energy needs are less, if we feed them what we would feed intact dogs, neutered
and spayed dogs will, of course, gain weight. In truth, most neutered and spayed dogs are
overfed and underexercised and are twice as likely to become obese as intact dogs. Neutering
and spaying in themselves do not cause obesity, it is how we care for the dogs afterwards that
predispose them to becoming overweight.

Genetics and breed predispositions:
Are some breeds simply more prone to becoming
overweight? The answer is yes. This does not mean
all dogs of that breed may have the tendency, but it
does mean owners of those breeds of dogs should be
especially vigilant about monitoring their dog's weight.
Those breeds which are more prone to becoming
overweight include Labrador Retrievers, Dachshunds,
Beagles, Cairn Terriers, Cocker Spaniels, Collies, Shetland Sheepdogs (Shelties), and Basset
Hounds. Other breeds tend to have a lower incidence of obesity. I do not think I have ever seen
an overweight Greyhound, but I am sure it does occur.

Genetic factors which influence the type and characteristics of fat produced by the body have
been shown to contribute to obesity in rats and mice. Such factors may occur in dogs.

Dogs tend to become overweight when they are between 2 and 12 years of age, especially
around the 6 year mark. As dogs become 'senior,' the tendency to become overweight
decreases. Young dogs, too, in general, are less likely to be overweight, since their energy
requirements are high since they are growing and are generally more active. A dog becoming
overweight when under two years of age is a real warning sign. This dog will tend to be
overweight his entire life, so weight reduction should occur as soon as possible and every effort
should be made to maintain the optimum weight.

Social environment:
Many people will acknowledge they eat more when they are stressed, and often eat less
nutritious food. For me, large amounts of chocolate come to mind. Animals have similar responses
to stress. This stress could include new persons entering the household (e.g.; a baby), changes
in the household routine, etc.

Some nutritionists feel dogs may overeat simply because they are bored and there literally is not
much else to do. Some dogs may not get into the garbage can because they are hungry, but
because they need something to do - the food they find is just a bonus.

Dogs who live in a multi-dog or even multi-pet households often tend to eat more and/or faster
than those in one-dog households. The change in behavior when other animals are present is
called 'social facilitation.' The competition for food, whether perceived or actual, makes some
dogs much more focused on their food and can lead to obesity.

Physical Environment:
Maintaining body temperature is an energy-consuming task. When a dog is in an environment
with a temperature below freezing, his calorie requirements may increase by as much as 30%.
Conversely, an inside dog uses relatively few calories to maintain normal body temperature.

Various medications can influence metabolism and appetite. These include the glucocorticoids
such as prednisone and dexamethasone, the barbiturates such as phenobarbital which is used to
control epilepsy, and a class of drugs called benzodiazepines which includes valium.

The following possible contributors to obesity account for less than 5% of the cases of obesity in
humans, and a similar proportion is likely in dogs as well.

In the disease hypothyroidism, the dog's body produces
less thyroid hormone. Thyroid hormone influences metabolic
rate. Less thyroid hormone means lower metabolic rate and
lower energy needs. A normal dog will become overweight if
he develops hypothyroidism and is fed the same amount he
was  fed when he was healthy.

Depending on the breed, many veterinarians will check an
overweight dog for hypothyroidism before a weight reduction
program is instituted. It is very difficult to get a hypothyroid dog
to lose weight even when fed a weight reduction diet. By treating the hypothyroidism in
conjunction with starting a weight control program, chances of success are much higher.

Cushing's disease (hyperadrenocorticism):
Cushing's disease (hyperadrenocorticism) is a disease in which the adrenal gland produces too
high a level of glucocorticoids. Glucocorticoids can alter metabolism and cause an increase in
appetite and an increased deposition of fat. Again, in addition to starting a weight control
program, the Cushing's disease must be managed if the dog is to successfully lose weight.

An insulinoma is a tumor that occurs in the pancreas. It is a tumor consisting of the cells that
produce insulin. A dog with an insulinoma produces too much insulin. Insulin tends to increase
food intake and promote the generation of
tissue, including fat.

Adult onset diabetes:
If an increase in insulin can contribute to obesity it seems contradictory that diabetes mellitus, in
which there is decreased insulin production, could also contribute to weight gain. There is,
however, in dogs a type of diabetes called non-insulin dependent diabetes mellitus (
which obesity can occur. It is one of those 'which came first, the chicken or the egg' conditions.
It occurs when an overweight dog must increase his insulin production, which then causes an
increase in appetite and fat deposition. Then as the disease progresses, the production of insulin
can not keep up with the demand and increased blood glucose levels and increased fat
deposition occur. The dog ultimately becomes diabetic and severely obese.

Pituitary gland and brain diseases:
The pituitary gland is often called the 'master gland' because it produces hormones itself and
regulates the production of hormones from most of the other glands. If the pituitary gland is
functioning abnormally, changes in the levels of various hormones can change the dog's
metabolism, appetite, and fat deposition.

The hypothalamus in the brain regulates appetite. Hypothalamic abnormalities could account for
rare instances of increased appetite resulting in obesity.

Is Your Dog Overweight?


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Copyright © 1997-2004, Drs. Foster & Smith, Inc. All Rights Reserved.
Reprinted from
Humans are the main cause
of obesity in dog
Neutered and spayed dogs,
in general, need fewer           
calories than intact dogs.
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