See spot run: obesity doesn't have to be permanent
SEE SPOT RUN: OBESITY DOESN’T HAVE
system uses both visual cues and palpation of specific
TO BE PERMANENT
areas (the ribcage, waist, and dorsal spinous processes)
to estimate subcutaneous and abdominal fat
Debra L. Zoran, DVM, PhD, Diplomate ACVIM
accumulation relative to superficial muscles. This
technique is highly precise (repeatable), but not
Texas A&M University, College Station, TX
necessarily accurate. However, it is currently the most
well known and repeatable means of body condition
Obesity is the excessive accumulation of adipose
score assessment in the clinical setting and should be
tissue in body, and has been defined to occur when
used as part of the physical examination of all pets
dogs or cats are >30% over their optimal body weight. In
humans, criteria have been established for what defines
“overweight” and what is “obese,” and these criteria have
THE CAUSES OF OBESITY
generally been based on the body mass index. However,
The primary reason for development of obesity in any
no similar index for optimal body weight has been
animal is that they are consuming more energy than they
identified in dogs and cats, and thus the use of these
are expending. This can occur when a dog has
classifications has not been rigorously studied. However,
excessive dietary intake of calories (food and treats) or
in general, dogs are reported to be overweight when
when there is a reduction in energy expenditure
their body weight is 15% over their optimal body weight,
(reduced activity, illness or injury resulting in less
and obese when they are >30% over the optimum.
exercise, etc). There are some medical conditions and
Using these criteria, the incidence of obesity in dogs and
cats in the United States is reportedly between 30% and
endocrinopathies, such as hyperadrenocorticism and
40%. More alarming, however, is the suggestion that the
hypothyroidism, and drugs such as steroids and
incidence of obesity in our pet population is increasing
anticonvulsants. But the primary reason that weight gain
despite the many attempts to control weight with diet and
occurs in dogs on steroids or with hypothyroidism is that
exercise programs. This article reviews our current
they have either increased food intake or decreased
understanding of obesity in dogs, its important role in the
energy expenditure (or in some cases, both).
development of many diseases in dogs, and discusses
Nevertheless, in both instances, the primary reason for
the approach to management of obesity from dietary,
the development of obesity is still a positive energy
lifestyle and behavioral alterations to newer balance. While genetic factors are also likely involved pharmacologic options for management.
(eg, Labrador retrievers have a higher incidence of
obesity than is seen in other breeds of like size), the role
DEFINING AND MEASURING OBESITY
of inheritance in canine obesity needs more study. In
The first step in the evaluation of a pet that is
both dogs and cats, neutering is an important risk factor
overweight or obese is to make an assessment of the
due to the hormonal changes that occur that result in
degree of the problem. Assessment of body changes in levels of leptin, progestins, and other composition, or more specifically, attempting to separate
hormones that result in increased appetite, and reduced
fat mass from the lean body mass, has been energy metabolism and metabolic rate. The key factors approached by a wide variety of different methods;
for prevention of obesity in neutered animals appear to
unfortunately, none are ideal. The key is to find be careful control of intake immediately after neutering assessment methods that are precise, accurate, easy to
(no free choice feeding, reduction of intake by 25% to
do in a practice setting, and not excessively costly.
account for the hormonal changes resulting in reduced
However, many of the tests are precise, but not accurate
energy needs), and close monitoring of body weight and
(able to yield the same result on repeated analysis,
BCS to allow adjustments in intake if needed. In dogs,
irrespective of accuracy), and others lack both precision
there are a number of dietary factors that are also
and accuracy. The most precise and accurate tests that
associated with obesity, including the number of snacks
are used in research settings are costly, not easy to use
fed, especially table scraps, and the number of meals.
and are invasive, and thus are not ideal for clinical
Dogs that were allowed to be near their owners at
practice. Examples of the most common research tools
mealtime also had a greater tendency to be obese due
used for assessment of body composition include to the increased likelihood of receiving table scraps and chemical analysis, densitometry, dual-energy x-ray human food treats. In addition, because feeding dogs is absorptiometry (DXA), subcutaneous or visceral a social interaction, feeding and food interaction with the ultrasonography, CT or MRI. Thus, in the clinical setting,
dog can become a daily social interaction that can
the most widely used procedures to assess body become a problem resulting in overfeeding and composition are measurements of body weight or inappropriate food intake patterns. It has been shown morphometric measurements (eg, body condition that in households where the owners are health scoring, tape measurements or body mass index).
conscious (conscious of diet and nutrition, who exercise
Morphometry or the measurement of form is used to
regularly, and watch their own weight) they tend not to
assess body composition using different parameters that
have obese dogs. Thus, there are clearly human
can be measured. Body condition scoring (BCS) behavioral and “food is love” issues that have to be employs a subjective method of quantifying the body
considered in the development of obesity in dogs, and
composition based on 5-point or 9-point schemes. This
The North American Veterinary Conference – 2007
these must be addressed for successful weight control to
Dietary Therapy
There are two important goals in establishing an
appropriate dietary therapy regimen: 1) It must be
THE IMPORTANCE OF OBESITY AS A DISEASE
tailored to the individual animal (diet needs for allergy,
Obese humans generally do not live as long as their
renal disease, GI issues, etc), and 2) caloric restriction
lean counterparts, and are much more likely to suffer
must occur without concurrent protein starvation to
from obesity-related diseases such as type II diabetes,
prevent loss of lean muscle tissue during weight loss.
coronary artery disease, osteoarthritis, hypertension,
The first step in making a diet plan is to obtain a
and some cancers. Dogs and cats are susceptible to the
complete dietary history that gives an accurate
same detrimental effects, including decreased longevity,
accounting of all foods fed to a pet on a typical day. In
and development of a variety of disorders that are
some cases, it may be necessary to have the owners
associated with being obese. In a recent study, dietary
keep a diet log for a week, writing down the meals, the
calorie restriction was clearly shown to increase treats, the table foods, etc. consumed by the dog during longevity in a group of 24 Labrador retrievers. In that
that time. This is especially helpful in households where
study, the dogs in the energy-restricted group were fed
the dog may receive foods from more than one individual
75% of their counterparts, and the dogs lived an average
(especially children). In addition, it should be noted if the
of two years longer and had a reduced incidence of hip
dog has access to any other foods (other pets in the
dysplasia, osteoarthritis and glucose intolerance. Other
family, outside scavenging), if the pet received
problems that were found to be more common in obese
medications in foods, and if there are other food items
dogs compared to the dogs that were of ideal body
available to the dog (chew treats, dental chews, etc).
condition include heat intolerance, increased anesthetic
The next step in designing a diet plan is to decide
risk, increased difficulty with routine clinical procedures
upon a weight loss goal. The goal does not necessarily
(catheter placement, palpation, imaging), and prolonged
have to be that the pet achieves its ideal body weight –
this goal should be based on the pet, the owner’s
There are a number of diseases in dogs and cats are
situation and goals, and the ability to reach the goal. It is
reported to be associated with obesity, including important to set reasonable goals that can be achieved, orthopedic diseases, diabetes, heart disease, abnormal
rather than overly ambitious goals that are not likely to
circulating lipids, certain cancers, urethral sphincter
be achieved and result in the client becoming
mechanism incompetence, dyspnea due to discouraged because their pet is not meeting the compromised ability to breathe (eg, laryngeal paralysis,
expected goal. A step down approach to weight loss is
brachycephalic syndrome, tracheal collapse etc), heat
much more likely to result in success and continued
intolerance, decreased immune function, and dystocia to
owner persistence, than a goal that is too ambitious and
name just a few. Further, we do not have a complete
results in the owner abandoning the process due to lack
understanding of the inflammatory role of obesity of progress. Once you have set the appropriate weight hormones in our pets, and this could lead to an even
loss target for that pet, then you can calculate the energy
greater connection between obesity and disease. Finally,
restriction that will be required to achieve the goals you
as we have previously shown from the prospective study
have set. Ideally, the best way to set the new energy
of calorie-restricted dogs, dogs that are obese also do
intake is to reduce intake to 60% to 80% of the pet’s
not, on average, live as long as their leaner current intake. If the pets intake is not known (or cannot counterparts. The bottom line is that prevention of
be calculated accurately), then it is necessary to
obesity in dogs can increase both the quality and
calculate an estimate of intake for the target weight.
There are a number of different equations recommended
for calculating maintenance energy requirements, and
TREATMENT OF OBESITY: FROM DIET TO DRUGS
ones the most frequently used will be discussed. Finally,
The management of obesity in dogs has long been
another way that you can calculate calorie reduction is to
focused on reducing energy consumption (dietary calculate the energy content of the amount of fat mass management) and increasing energy expenditure you wish the pet to lose (eg, 1 kg adipose tissue = 7700 (exercise). And, while this approach is very effective
kcal) Take this number and divide by the number of
when it is implemented completely, it can be quite
days you plan to feed the weight reduction diet. That
difficult to overcome the behavioral, social, metabolic,
number is subtracted from the dog’s current intake to
and hormonal influences of obesity and achieve long-
achieve a new, lower number of calories for intake. This
term success. In humans, obesity management options
method is more cumbersome, but is based on a more
include dietary management, exercise, behavior precise estimate of fat loss. Nevertheless, no matter modification, pharmacologic therapy, and surgery. At this
which approach is used, the key to success is first to
point, surgical therapy of obesity in dogs and cats is an
have complete client cooperation, then to monitor the pet
ethically gray area. Unfortunately, there have been no
frequently (eg, every 3–4 weeks), and finally to make
drugs licensed for weight loss in dogs or cats, and that
adjustments in intake as needed based on the plan you
has limited the potential therapeutic options for have developed. To be sure of accuracy in the weight veterinarians and pet owners. In this section, the dietary,
loss period, it is important to weigh the pet on the same
behavioral, physical and potential pharmacologic scale. To provide safe, but efficient weight loss, the dog approaches to obesity management will be discussed.
should not lose more than 1–2% of its body an appetite suppressant, as lipase inhibition may result weight/week.
in an increase in CCK (cholecystokinin) release resulting
In addition to reducing the energy intake of pets that
in satiety signaling. In contrast to orlistat, sibutramine is
are overweight, it is also possible to increase weight loss
a noradrenergic and serotoninergic re-uptake inhibitor
by increasing energy expenditure through increased
that enhances both satiety and thermogenesis (energy
exercise. In obese dogs, as in obese humans, it is
metabolism). This effect is identical to the effect
important to start slow with an exercise program, and
produced by fenfluramine (one of the drugs in the
only very gradually and slowly increase the duration and
previously available, now off the market, combo drug
intensity of the exercise. In some dogs, exercise may be
Fen-Phen (Phentermine) in that it reduces hunger and
impossible, due to severe joint problems or exercise
increases satiety. The most important potential risk from
intolerance or due to inability of the owners to exercise
the use of sibutramine is its sympathetic activity, as it
with their pet. In these dogs, very minimal activity, or low
has been shown to increase heart rate and blood
impact activity, such as a treadmill or water treadmill
pressure, which is very important in patients that have
may be needed to allow safe, non-painful activity.
preexisting heart or kidney disease, or hypertension. In
Consultation with a veterinary physical rehabilitation
addition to these two drugs, which have been used for
specialist is often very helpful in determining appropriate
weight loss, but have their limitations, a number of
activities for the dog. This can also be part of the overall
compounds are currently under investigation or are in
diet and weight reduction plan, as the weigh-ins and
clinical trials. One of these drugs is Rimonabant, an
evaluation of the pet’s progress can occur in conjunction
endocannabanoid CB1 receptor inverse agonist, that
with the visits to the rehabilitation program.
works by appetite suppression and reduction of food
Many dogs become obese due to the social bonding
intake. The drug is currently in multiple phase III clinical
that occurs with owners and their dogs during feeding.
trials and may become one of the newest members of
This human–animal bond activity results in a strong
the pharmacologic armamentarium. Topiramate, a newer
behavioral component to the development of obesity that
anticonvulsant drug, has also been shown to be an
must be addressed. In order to achieve success in
inhibitor of fat deposition and decreases intake.
changing these behaviors, it is important to substitute
However, at the doses required to induce weight loss,
low calorie treats, games, or grooming activities for table
significant side effects (psychomotor dysfunction) were
scraps or other high calorie treats. Begging for food is
observed. Currently the parent drug company is
more of a behavioral problem than a hunger problem,
reformulating the drug to attempt to develop a product
and if this relationship is not considered in weight loss
that may be both safe and effective for weight loss. At
programs, the plan is doomed to fail. In some cases,
this time, there are currently no drugs approved for use
consultation with a veterinary behaviorist is an important
in the United States for weight loss in dogs (although
part of the overall plan for weight loss.
there are several in the approval process), and only one
recently approved drug in Europe. The mechanism of
Other Therapeutic Options
action of the drug approved for weight loss in dogs is an
In addition to traditional therapies used for weight
MTP inhibitor whose mechanism of action is inhibiting
regulation or weight loss, there is increasing interest in
the digestion of fats. Thus, weight reduction occurs
other modalities (drug therapy, surgical options, primarily by reducing energy uptake from the GI tract. nutraceuticals) that may improve the odds of success.
Because of the difficulty in achieving weight loss in dogs,
The surgical approach has become increasingly and the sheer number of obese dogs, it is likely that important in the management of the disease in humans,
pharmacologic options for obesity management will
but in veterinary medicine this approach carries become an increasingly important part of the overall considerable ethical gray areas and will not be approach to the problem. discussed in this forum. However, there are currently
Nutraceutical therapy is also an increasingly
three different pharmacological approaches to weight
important aspect of therapy of weight loss. L-Carnitine,
management currently available for use in humans: an amino acid synthesized from methionine and lysine in 1) drugs that reduce fat uptake from the intestine,
the liver, has been used for several years to enhance fat
2) drugs that reduce appetite and 3) drugs that increase
metabolism and help maintain lean muscle mass during
metabolism (fat burning). Of these different types of
weight loss. Incorporation of 100–300 ppm of L-Carnitine
drugs, only two are currently approved for use in the US
into diets has been shown to reduce lean muscle mass
and they are orlistat (Xenical®) and sibutramine loss during weight loss lab animals, primarily due to (Meridia®, Reductil®). Orlistat is a derivative of a enhanced fatty acid oxidation and energy availability for lipostatin (isolated from a bacterium in the soil) that
protein synthesis. To date there are no carefully
inhibits gastrointestinal lipases. Thus, the mechanism of
controlled studies in dogs that confirm the effectiveness
action is that it blocks the breakdown of ingested dietary
of carnitine in weight loss, but it is a reasonable and safe
fat by preventing breakdown of triglycerides into nutraceutical therapy. Other nutraceutical alternatives monoglycerides and fatty acids that can be packaged
that may enhance weight loss, but require additional
into micelles and absorbed. The undigested fat is
evaluation include conjugated linoleic acid (CLA) and
excreted in feces, and thus the primary side effect of
dietary diacylglycerol (DAG). The role of nutraceutical
orlistat therapy is development of steatorrhea and therapy will likely continue to grow as approaches to diarrhea. In addition to these effects, orlistat may also be
The North American Veterinary Conference – 2007
dietary therapy continue to be researched to seek new
6. Kealy RD, Lawler DF, Ballam JM, et al. Effects of
diet restriction on life span and age related changes
in dogs. J Am Vet Med Assoc 2002;220:1315-1320.
Suggested Reading
7. Fascetti AJ. Obesity management in dogs and cats.
1. German AJ. The growing problem of obesity in dogs
8. Michel KE. Designing an effective weight reduction
2. Burkholder WJ. Precision and practicality of
program. Proc Atlantic Coast Vet Conf, 2002.
methods assessing body composition of dogs and
9. Umeda T, Bauer JE, Otsuji K. Weight loss effect of
cats. Compend Contin Educ Pract Vet2001;23:1-10.
dietary diacylglycerol in obese dogs. J Anim Physiol
3. Mawby DI, Bartges JW, d Avignon A, et al.
Comparison of various methods for estimating body
10. Halford JCG. Clinical Pharmacotherapy for obesity:
fat in dogs. J Am Anim Hosp Assoc 2004;40:109-
Current drugs and those in advanced development.
4. Trayhum P, Bing C, Wood, IS. Adipose tissue and
11. Macintosh MK. Nutrients and compounds affecting
adipokines – Energy regulation from the human
body composition and metabolism. Compend Contin
perspective. J Nutr 2006;136:1935S-1939S.
5. Armstrong PJ, Lund EM, Kirk CA, et al. Prevalence
12. Yaissle JE, Holloway C, Buffington CAT. Evaluation
and risk factors for obesity in dogs and cats. Proc
of owner education as a component of obesity
treatment programs for dogs. J Am Vet Med Assoc2004;224:1932-1935.
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