Abnormal Weight Loss in Cats

Why is my cat losing weight?

Weight loss in cats can be associated with many normal and abnormal conditions. This handout discusses weight loss that is unintentional. If your cat is on a weight-loss diet, and you are concerned they are losing too much weight, consult your veterinarian.

Weight loss is considered clinically significant when a cat loses more than 10% of their normal body weight and the change is not caused by fluid loss or dehydration. For example, a healthy cat that weighs 10 pounds would have to lose more than 1 pound for the weight loss to be considered clinically significant.

Changes in diet, environment, or stress levels, including the addition of new pets, may cause weight loss. However, this weight loss is rarely permanent or significant. The faster your cat loses weight, the more concerning the change is.

What is causing my cat to lose weight?

Cats lose weight when they take in fewer calories than their body requires. This imbalance may be caused by the following factors:

• High energy demand associated with excessive physical activity or prolonged exposure to a cold environment
• A hypermetabolic state, during which the body burns calories more quickly due to an underlying illness
• Inadequate or poor-quality diet
• Insufficient food intake due to lack of appetite (anorexia), swallowing disorders, or regurgitation
• Malabsorption or maldigestion disorders (a decreased ability to digest or absorb nutrients from food)
• Excessive loss of nutrients or fluid from vomiting, diarrhea, or excessive urination

What other signs should I look for?

Weight loss can be caused by disorders in the body's organ systems and weight loss can also affect all organ systems. Questions that may provide insight into the cause of your cat's weight loss include:

• Is your cat's appetite normal, increased, or decreased?
• What kind of food are you feeding your cat?
• How much food are you feeding your cat?
• How and where do you store your cat food?
• Has your cat’s activity level changed?
• Does your cat have any trouble chewing or swallowing?
• Have you observed any regurgitation or vomiting?
• Has your cat been drinking and urinating more or less than normal?
• What color and consistency are your cat's stools?
• Is there a change in the volume or frequency of stools?
• Has your cat been spayed or neutered?
• Does your cat have a fever or seem excessively tired?
• Is your cat tested and/or treated regularly for intestinal parasites?
• Is your cat on any other medications or supplements?

How can the cause of my cat's weight loss be diagnosed?

Your veterinarian will obtain a thorough medical history and perform a nose-to-tail physical examination. Additional testing, including blood and urine laboratory tests, X-rays, blood pressure, and possibly an abdominal ultrasound may also be recommended.

What common diseases cause weight loss?

Many diseases can cause weight loss. In fact, most chronic diseases result in weight loss at some point during the disease. Some of the more common conditions associated with weight loss include the following:

• Anorexia (lack of appetite) due to a behavioral condition or disease. Causes are widespread and can include cancer, infectious diseases, and diseases of the major organs (heart, liver, kidneys, gastrointestinal tract, central nervous system).
• Decreased nutritional intake caused by loss of smell, inability to grasp or chew food, swallowing disorders, or regurgitation.
• Prolonged vomiting or diarrhea.
• Malabsorptive disorders that inhibit absorption of nutrients from the intestinal tract, such as inflammatory bowel disease, cancer of the gastrointestinal tract, or severe intestinal parasitism.
• Maldigestion disorders that interfere with the body's ability to break down food into usable nutrients, such as exocrine pancreatic insufficiency.
• Diseases that affect metabolism such as diabetes mellitus, hyperthyroidism, hyperaldosteronism, hypoadrenocorticism (Addison’s disease, rare in cats), and cancer.
• Neuromuscular disease resulting in weakness or paralysis.
• Increased caloric demand associated with excessive physical activity, prolonged exposure to cold, pregnancy or lactation, and fever.

What can be done to treat my cat's weight loss?

Treatment will be determined by the specific cause of your cat's weight loss. Once your veterinarian makes a diagnosis, they will initiate treatment to resolve the problem or improve your cat's quality of life. They may recommend diet changes, medications, or other treatments that address your cat’s specific problems.

What is the prognosis for my cat's weight loss?

The prognosis ranges from good to poor, as it depends on your cat's specific diagnosis. A thorough medical history, complete physical examination and appropriate diagnostic testing will assist your veterinarian in determining both the prognosis and the best course of treatment for your pet.