Weight changes in dogs and cats aren’t always caused by eating too much or too little. Sometimes, an unexpected shift in your pet’s weight is one of the earliest signs of an underlying medical condition.

Many pet owners assume that if their pet is gaining weight, they simply need less food or more exercise. While diet and activity play an important role, changes in your pet’s weight can sometimes indicate an underlying illness that requires veterinary attention.

Whether your dog is putting on weight unexpectedly or your cat is losing weight despite having a healthy appetite, it’s important not to ignore these changes.

At Clyde Veterinary Hospital, we believe that your pet’s weight is one of the most valuable indicators of their overall health. Early diagnosis of many medical conditions can lead to more effective treatment and a better quality of life.

Why is My Dog or Cat Gaining Weight?

Weight gain is one of the most common reasons owners seek veterinary advice. While overfeeding and lack of exercise are frequent causes, they are not the only explanation.

Excess weight places additional strain on your pet’s:

• Joints
• Heart
• Lungs
• Liver
• Hormonal system

This increases the risk of arthritis, diabetes, reduced mobility and a shorter lifespan.

However, some medical conditions can also cause weight gain or make your pet appear overweight, particularly in dogs.

Hypothyroidism in Dogs

Hypothyroidism is one of the most common hormonal disorders in middle-aged and older dogs. When the thyroid gland doesn’t produce enough thyroid hormone, the body’s metabolism slows significantly.

Common signs include:

• Unexplained weight gain
• Lethargy or sleeping more than usual
• Exercise intolerance
• Hair loss or a dull coat
• Recurrent skin or ear infections
• Feeling cold more often

The good news is that hypothyroidism is usually diagnosed with a simple blood test and is highly manageable with lifelong medication.

Cushing’s Disease in Dogs

Cushing’s disease (Hyperadrenocorticism) occurs when the body produces excessive amounts of cortisol, often called the stress hormone.

Dogs with Cushing’s disease often appear to have gained weight, although much of their appearance is caused by muscle loss and fat redistribution.

Signs of Cushing’s disease include:

• A rounded or “pot-bellied” abdomen
• Increased thirst
• Increased urination
• Increased appetite
• Excessive panting
• Thin skin
• Hair loss
• Muscle weakness

Early diagnosis allows treatment to begin sooner and can greatly improve your dog’s quality of life.

Why is My Dog or Cat Losing Weight?

Unexpected weight loss should never be ignored, especially if your pet is eating normally or even eating more than usual.

Weight loss often indicates that the body is unable to properly absorb or utilise nutrients, or that another disease process is affecting your pet’s health.

Diabetes Mellitus in Dogs and Cats

Diabetes prevents the body from using glucose effectively, causing pets to lose weight despite having an increased appetite.

Other common signs include:

• Drinking much more water
• Urinating more frequently
• Increased appetite
• Lethargy
• Cataracts or cloudy eyes (particularly in dogs)

Early diagnosis and treatment can help pets with diabetes live happy, healthy lives.

Hyperthyroidism in Cats

Unlike dogs, older cats commonly develop an overactive thyroid gland (hyperthyroidism).

This condition speeds up the body’s metabolism, causing affected cats to lose weight even though they often eat more than ever.

Signs include:

• Weight loss despite a good appetite
• Increased thirst
• Increased activity or restlessness
• Excessive vocalisation
• Rapid heart rate
• Poor coat quality

Hyperthyroidism is one of the most common diseases seen in senior cats and can often be successfully managed once diagnosed.

Cancer or Internal Masses

Cancer can cause gradual weight loss long before other obvious symptoms develop.

Depending on the location of the tumour, pets may also experience:

• Reduced appetite
• Vomiting
• Diarrhoea
• Lethargy
• Changes in behaviour
• Difficulty breathing
• Abdominal enlargement

Early investigation provides the greatest opportunity for diagnosis and treatment.

Other Medical Conditions That Can Cause Weight Loss

Weight loss can also be associated with:

• Chronic kidney disease
• Liver disease
• Gastrointestinal disease
• Pancreatic disease, including Exocrine Pancreatic Insufficiency (EPI)
• Dental disease causing painful eating
• Chronic infections
• Intestinal parasites

Why Regular Weight Checks Are So Important

Your pet’s weight tells us much more than simply whether they’re overweight or underweight.

At Clyde Veterinary Hospital, every weight assessment includes consideration of:

• Body Condition Score (BCS)
• Muscle Condition Score
• Appetite and thirst
• Energy levels
• Physical examination findings
• Whether blood tests, urine testing or diagnostic imaging may be recommended

Sometimes a weight change has a simple explanation. Other times, it provides one of the earliest clues that an underlying medical condition is developing.

Detecting disease early often means more treatment options, lower treatment costs and a better long-term outcome for your pet.

When Should You Book a Veterinary Health Check?

We recommend arranging a veterinary examination if your dog or cat is:

• Gaining weight unexpectedly
• Losing weight without trying
• Developing a rounded or pot-bellied appearance
• Drinking significantly more water
• Eating much more or much less than usual
• Becoming less active
• Sleeping more than normal
• Simply not behaving like themselves

Helping Your Pet Live a Longer, Healthier Life

Changes in your pet’s weight should never be dismissed as “just getting older.”

Whether the cause is obesity, a hormonal disorder, diabetes, kidney disease or another medical condition, identifying the problem early gives your pet the best chance of successful treatment and a healthier future.

If you’ve noticed any changes in your dog’s or cat’s weight, our experienced veterinary team is here to help.

Book an Appointment Today