Page 462 - Problem-Based Feline Medicine

454 PART 7 SICK CAT WITH SPECIFIC SIGNS

of evidence for a concurrent disorder causing Primary obesity is best treated by offering a
euthyroid sick syndrome. hypocaloric diet designed for weight loss in cats.
– If there is a history of treatment for hyperthy- These diets generally have reduced fat and higher car-
roidism, the above findings plus response to bohydrate than maintenance diets, and a higher con-
therapy are sufficient for a diagnosis. centration of essential nutrients. Some are also high in
– If naturally occurring hypothyroidism is sus- fiber. Newer weight-loss diets for cats have restricted
pected, additional testing is recommended. carbohydrate (<25% ME) and are high in protein.
Similar to testing for hypothyroidism in dogs,
A satiety effect of insoluble fiber (e.g. cellulose) used
interpretation of tests is controversial.
as a bulking agent has not been proven in cats, and
– TSH response tests using animal-origin TSH
foods rich in such fiber increase the risk of constipa-
have been used in the past, but such TSH is no
tion. Fermentable fiber may promote satiety.
longer widely available. Recombinant human
TSH is now available, and protocols using this Because some obese cats have very low metabolic
preparation should be defined in the future. rates, it is best to calculate the amount of energy being
– TRH response test may be used: Obtain baseline consumed by the cat, and then reduce energy fed to
serum sample, give 0.1 mg/kg IV, obtain post 80% of current consumption. Using current energy
serum sample at 4 hours. A normal response is a consumption as a basis for restricting calories, makes it
> 50% increase from baseline. more likely that successful weight loss will be achieved
– The assay for canine TSH has been used anec- in the first month of the program, which makes it more
dotally but has not been validated for the cat. likely the owner will continue the program.
– Thyroid biopsy may be obtained, demonstrating ● If current energy consumption cannot be deter-
atrophy or thyroiditis. mined, a guideline is to offer 60–75% of energy the-
– If there is a response to therapy, thyroid supple- oretically required for maintenance of ideal body
ment can then be withdrawn to observe for weight (i.e. 60–75% of 60 kcal/kg ideal body
recurrence of signs. weight/day) and adjust every 2–4 weeks to achieve
a loss of about 1% of body weight per week.
Differential diagnosis At 1% weight loss per week, about 90% of weight will

The principal cause of abdominal distention that may be lost from fat and <10% from lean body tissue. More
be confused with fat is fluid. However, many cats with severe calorie restriction decreases the proportion lost
ascites are chronically ill and have muscle wasting. from fat and increases the proportion of weight lost
from lean body tissue. Losses of body weight greater
Pregnancy – in pregnant cats the degree of abdominal than 2% per week are dangerous as hepatic lipidosis
distention may be disproportionate to the amount of may develop. During a weight loss program it is impor-
subcutaneous fat. tant to verify that the cat is eating regularly. Fasting will
Obesity is a common disorder and may make diagnosis increase the risk for developing hepatic lipidosis.
of other concurrent causes of abdominal distention dif- It is important not to restrict calories by restricting protein.
ficult by interfering with palpation.
Dietary additives may help promote weight loss and/or
ameliorate secondary glucose intolerance, and are
Treatment
being added to commercial diets for cats.
For successful management of obesity, it is essential ● l-carnitine increases fatty acid oxidation and pro-
that the owner is committed to the goal that their cat motes fat loss, while preserving muscle mass. It
achieves a healthy body weight. The owner needs to also appears beneficial in treating cats with hepatic
understand and believe that appropriate management of lipidosis. Supplemental l-carnitine can be dosed
obesity leads to a more active and healthier pet, and a orally (250 mg/cat q 24 h of pharmacological grade
longer life of their pet. The evidence that only 53% of product added to food or formulated as aqueous
obese cats were alive after 4 years compared to 83% suspension).
of cats with optimum body weight may help to con- ● Vitamin A promotes weight loss by stimulating
vince some owners of the importance of weight loss. uncoupling protein formation, which increases