Six key causes of unexplained canine weight gain

Unexplained weight gain in dogs can be worrying for owners, especially when diet and exercise habits have not changed. In the UK, many dogs carry excess weight, but if your dog’s weight increases without a clear reason, it may signal an underlying health issue. This guide explores six common health conditions that may lead to unexpected weight gain in dogs and how to recognise them.

1. Hypothyroidism: Slowed Metabolism Causing Weight Gain

Hypothyroidism is an endocrine disorder where the thyroid gland produces insufficient hormones, especially T3 and T4. These hormones regulate metabolism, and when levels are low, the dog’s metabolic rate slows. This results in weight gain despite no increase in food consumption.

Affected dogs may also show lethargy, cold intolerance, dull or thinning coat, and dry skin. Diagnosis requires a vet to perform blood tests to measure thyroid hormone levels. Synthetic hormone replacement therapy can usually restore normal metabolism and help regain a healthy weight.

2. Cushing's Disease: Hormonal Imbalance Leading to Potbelly

Canine Cushing's disease or hyperadrenocorticism results from excessive cortisol production by the adrenal glands, often causing fat redistribution and a characteristic potbelly appearance. Dogs may also display increased thirst and urination, muscle loss, hair thinning or hair loss, and fragile skin prone to bruising.

This condition requires veterinary diagnosis by hormone assays and imaging. Treatment can involve medication to reduce cortisol production or, in some cases, surgery. Early management improves quality of life.

3. Intestinal Parasites: Hidden Causes of Abdominal Distension

Intestinal parasites like tapeworms or whipworms can cause nutrient malabsorption and varying weight changes. Though parasites usually lead to weight loss, a heavy infestation may cause your dog’s abdomen to appear distended or bloated, mimicking weight gain with a potbellied look.

Regular worming is essential to protect your dog’s health and prevent parasite-related weight changes. If your dog shows abdominal swelling or gastrointestinal symptoms, consult your vet for appropriate parasite control.

4. Fluid Retention: Weight Gain From Underlying Organ Issues

Some heart, kidney, or liver diseases can cause fluid to accumulate in the abdomen or chest cavity, termed fluid retention or oedema. This can lead to a swollen, bloated appearance without actual fat gain, making your dog seem overweight or heavier.

Fluid retention often signals a serious health problem requiring urgent veterinary investigation and treatment. Frequent veterinary check-ups and prompt attention to any swelling are essential to manage these severe conditions.

5. Medication Side Effects: Unintended Weight Changes

Certain medications, especially corticosteroids prescribed for allergies, inflammation, or autoimmune diseases, can increase your dog’s appetite and cause water retention, both contributing to weight gain. Some drugs may also reduce activity levels, further influencing weight.

It is important to discuss potential side effects with your vet when starting any medication. Adjustments to diet and exercise can help manage weight changes during treatment.

6. Pregnancy: Expected but Often Overlooked Weight Gain

For unspayed female dogs, pregnancy naturally leads to weight gain as puppies develop. This can sometimes be mistaken for unexplained weight gain, especially in rescue dogs or when spay status is unknown.

Knowing your dog’s reproductive status is vital. If unsure whether a female is spayed, consult with your vet. Pregnancy signs include progressive abdominal enlargement and behavioural changes. Veterinary care during pregnancy helps ensure both mother and puppies remain healthy.

When to Visit Your Vet

If your dog is gaining weight without a clear dietary or lifestyle reason, or if you notice other symptoms such as lethargy, increased thirst or urination, hair loss, or abdominal swelling, seek veterinary advice. Early diagnosis of underlying conditions like hypothyroidism or Cushing’s disease is crucial for effective treatment and improved long-term health.

Remember, responsible pet ownership includes regular health checks and weight monitoring to maintain your dog’s wellbeing.