Six health conditions behind unexplained canine weight gain

Six health conditions behind unexplained canine weight gain

Health & Safety

It is a simple fact that more than half of the UK’s canine population are carrying some excess weight, whether this be just a couple of lb or significant obesity. Getting the balance between diet and exercise right, as well as accommodating for the age and energy levels of your dog can be a challenge, and it is important to monitor your dog’s weight on an ongoing basis to ensure that they are kept fit and healthy.

If you do notice that your dog is gaining weight, it is usually relatively simple to suss out why, and reviewing your dog’s feeding protocols and how active they are to place them on a more suitable feeding plan can usually correct the problem before your dog becomes significantly overweight.

But what if your dog seems to be gaining weight for no obvious reason, when they are still as active as they ever were, and are not eating any more food? There may be a health condition behind it. Read on to learn more about six health conditions that commonly lead to otherwise unexplained weight gain in the dog.


Hypothyroidism is a hormonal condition caused by an underactivity of the body’s thyroid gland, which is responsible for producing hormones and enzymes that manage the digestive system and metabolism, and keep your dog’s weight within normal parameters. The thyroid produces several hormones, with the main ones being T3 and T4, and if either of these hormones are either not being produced at all, or not being produced in sufficient quantities, this can lead to significant weight gain in the dog, as their metabolism slows down.

You will need to get your dog checked out by the vet in order to run some tests on their thyroid function and hormone levels, and if your dog is diagnosed with hypothyroidism, the prescription of synthetic replacement hormones will usually return your dog to their normal, healthy weight.

Cushing’s disease

Canine Cushing’s disease is also known as hyperadrenocorticism, and is caused by an overproduction of the body’s glucocorticoid levels, which are a type of corticosteroid. Both natural and synthetic steroids can lead to weight gain and a range of other associated symptoms, and if the adrenal gland of the dog’s body does not regulate their glucocorticoid levels properly, weight gain, often with a pot-bellied appearance can occur, along with other symptoms such as hair loss and muscle weakness.

Again, pop your dog along to the vet for diagnosis and treatment.

Intestinal parasites

Intestinal parasites or worms attach themselves to the walls of your dog’s intestines, taking the nutrients from your dog’s food and sometimes leading to weight loss. However, a high parasite count, such as if your dog is infested with worms like tapeworms or whipworms can also lead to your dog’s abdomen becoming taut and distended, making it look bigger than it really is, and again, causing a pot-bellied appearance. Ensure that your dog is regularly wormed, in order to resolve the issue and prevent a recurrence.

Fluid retention

Certain canine health conditions can also lead to fluid retention as a side effect of the condition, which can lead to your dog appearing to be much fatter than they really are, with a bloated stomach and generally, overweight appearance. Some common veterinary conditions that are often accompanied by fluid retention include congenital heart defects, certain other heart diseases, and kidney and liver conditions.


Some medications that may be prescribed to your dog to help to treat other conditions can also lead to weight gain, although your vet should make you aware of this when they provide you with the medication. Any medication has the potential for generating a range of secondary symptoms, and you should learn about these in detail and work with your vet to decide upon the best course of action for your own dog.

Some medications too can cause your dog to become more lethargic or sedentary than usual, which may mean that you will need to alter their food intake to accommodate for this.


It may seem obvious, but pregnancy in the unspayed bitch can also of course lead to weight gain, and if you adopt or rescue a dog and she is entire, or you cannot confirm for sure that she has been spayed, this is something to be aware of!

Checking out our article on how you can tell whether or not a female dog has been spayed is a good place to start, and it is worth bearing in mind that if your unspayed female bitch suddenly seems to be getting progressively heavier around the middle, she may be carrying a litter! Again, your vet can examine your dog and let you know for sure, as well as advising you on the best time to have her spayed.

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