E950
Weight Loss


Introduction: Weight loss is a very non-specific sign of illness. Non-specific means that it may occur with a variety of illnesses and does not necessarily point to any one illness over any other. Because so many diseases cause an animal to lose weight, it is also one of the most common signs of illness. Weight loss is usually accompanied by other clinical signs, which together, help guide the doctor toward a diagnosis. In those occasional cases where weight loss is the only symptom noted, the diagnosis may be very difficult to obtain and extensive testing may be necessary before the doctor is able to determine the cause.

It is important for cat owners to be acquainted with the normal weight of each pet. In general, weight loss is not difficult to document. Quite often, animals will be taken to the veterinary clinic for perceived weight loss, weighed at the hospital, and comparing the current weight to that from previous visits, found to have gained a pound or two! One method of monitoring weight in cats is to use a bathroom scale. The owner should weigh him or herself and then pick up the family pet and weigh him or herself again while holding the animal. The difference between the two weights gives a general idea of how much the cat weighs. A more precise scale is often needed, and can usually be found at a local veterinary hospital. Most veterinary hospitals are happy to have owners bring their pets in for regular weigh-ins. Whatever the method used for weighing, it is important to keep a running record of the petís weight; therefore, weight changes may be documented and can be used as early detection information should an illness arise.

Causative Agents: Most causes of weight loss can be categorized into three major groups. These causes include, but are not limited to, the following:

  1. Insufficient protein levels being consumed - This can occur with inadequate protein levels in the diet or in problems that cause an animal to decrease its normal food consumption.
  1. Dental and mouth problems
  2. Unpalatable (poor taste/texture) food, poor quality diet, insufficient food offered, or too much competition for food for a less assertive pet.
  3. Environmental stress (excessive cold or heat)
  4. Systemic illness and other causes of anorexia. Please see page E36 for information on Appetite Changes.
  1. Protein being lost - This is most often associated with some type of disease process such as:
  1. Kidney disease
  2. Liver disease
  3. Diarrhea
  4. Vomiting
  5. Parasite infections
  6. Some skin conditions
  7. Severe burns
  8. Diabetes mellitus
  9. Problems with digestion or absorption of nutrients (i.e. pancreas malfunction)
  1. Hypermetabolism - Protein is being consumed at a rate that exceeds normal protein intake.
  1. Cancer
  2. Hyperthyroidism

Diagnosis: Because weight loss is a non-specific sign of illness, and the list of potential causes is long, a diagnosis may be difficult to obtain. A veterinarian will usually rely heavily on the history and the presence of other clinical symptoms to direct the formation of a diagnostic plan.

It is important to keep a record of a petís weight. Most veterinary hospitals are happy to have owners bring their pets in for regular weigh-ins.

The diagnostic plan begins with a thorough history, followed by a physical examination performed by a veterinarian. A variety of tests may then be indicated, beginning with a minimum data base. A minimum data base includes a CBC, blood (serum) chemistry profile, urine analysis, and sometimes radiographs. Still, further testing may be required in some cases before the exact cause can be identified. For additional information on the above tests, see Section D of this manual.

Treatment: Treatment of the underlying cause is essential. Situations where the weight loss is caused by a poor quality or unpalatable diet are usually corrected relatively easily. Other underlying causes may be more challenging to treat. Correction or management of the underlying cause, if possible, will usually result in improvement.

* If questions arise regarding nutrition, refer to page A575.