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3 Reasons Why Your Dog may be Gaining Weight

Have you been trying to help your dog lose weight but whatever you do they are still piling on the pounds?  Sometimes even with our best efforts we may not get the desired outcomes for our pets. But maybe it’s not as simple as we think… 

In this blog post we are going to explore 3 underlying causes that may affect your dog’s ability to lose weight.

IMPORTANT NOTICE: If at any point you’re reading this article and become concerned about your dog we highly recommend you talking to your vet for specific advice and action for your pet. 

Cushing’s Disease (hypoadrenocorticism) 

The first disease that we will be talking about is cushing’s disease. This is a disease that is common in middle aged or older dogs and can be quite commonly diagnosed (Blue Cross, 2019). 

What is Cushing’s Disease?

As part of both ours and a dog’s normal bodily function we produce a hormone called cortisol. As well as being involved in the stress response it is also involved in many other processes within the body including:

  • Metabolism control 
  • Blood pressure regulation 
  • Blood sugar regulation 
  • Immune system response 
  • Inflammation regulation 

(Sandia Animal Clinic, 2020) 

A normal response to stress would result in the release of cortisol to prepare the body for a perceived stressful event i.e. increasing the metabolism and triggering the release of energy from stores in the body. In dogs with Cushing’s the body overproduces cortisol. 

Clinical Signs of Cushing’s 

Due to the increase in cortisol, you may notice that your dog has an increase in thirst and in turn needing to be let out to the toilet more frequently. These are usually the most common signs that you will notice. However there are other clinical signs that you may also notice, such as:

  • Hair loss 
  • Lethargy 
  • Bloated or ‘pot bellied’ appearance 
  • Weight gain 

Diagnosis and Treatment of Cushings

Although there are a few different underlying causes for Cushing’s disease, the diagnosis of the condition can be done with a few different tests. 

A blood test can be performed called an ACTH Stimulation test. This is a blood test that can be performed and sent away to an external laboratory to test the body’s response to the administration of steroids. Two samples are taken, thye first before the administration of a drug that stimulates a cortisol response, the second one hour after the administration of this drug.  

If your vet suspects that there is another cause for the overproduction of cortisol, it may be recommended by your vet that your dog have an ultrasound scan performed. 

Whilst this disease may show similar symptoms to another disease called hypothyroidism, it is important to note that if you are at all concerned about your pet, it is best practise to speak to your registered vet for further advice. 


Signs of hypothyroidism can be similar to Cushing’s disease we have talked about above. But the cause of this disease is very different. Located at either side of your dog’s windpipe are two glands called the thyroid glands

They are responsible for the production of thyroid hormone which is involved in your dog’s metabolism but also their ability to regulate their temperature (Southwind Animal Hospital, 2022). 

Whilst the cause of this disease is not fully understood, the most common presentation is when the immune system attacks the thyroid glands which is known as idiopathic hypothyroidism

Clinical Signs of Hypothyroidism

As we discussed in the Cushing’s section, some of the clinical signs for hypothyroidism are similar, so it is important to speak to your vet for advice regarding these conditions if you suspect your dog is displaying any of these symptoms:

  • Loss or thinning of the fur 
  • Dull coat 
  • Excessive shedding or dandruff 
  • Weight gain 
  • Reduced activity/lethargy 
  • Reduced ability to tolerate the cold 

(College of Veterinary Medicine – Washington, 2021) 

Diagnosis and Treatment of Hypothyroidism

Diagnosis of hypothyroidism is typically done with a single blood test that is sent away to an external laboratory for analysis. If the results confirm the diagnosis then your dog will start being treated with an oral medication that they will need to stay on indefinitely. 

Further blood tests may be required to make sure that the medication dosage is correct at certain intervals but this may also be at the discretion of the vet in charge of your pets care. 


Although arthritis may not directly cause weight gain in dogs like the two conditions described above, it is still important to highlight the complications it can present when trying to get your dog to lose weight. 

Arthritis is commonly seen in older dogs but it can also affect younger dogs with skeletal deformities or as a result of trauma experienced. Arthritis is an inflammatory based disease that affects the cartilage surrounding your dogs joints (Animal Trust, 2022). 

Clinical Signs of Arthritis 

In normal joint anatomy the cartilage is smooth making it easy for joints to flex and withstand movement. With arthritis the surface of this cartilage becomes damaged meaning that the joint does flex as well and even sometimes mean that the bones rub together which can be painful for your dog. 

As a result of the bones rubbing together this can cause a reduction in your dog mobility, as well as observing stiffness and even swelling around the joints. 

Diagnosis and Treatment

Unlike the previous diseases we have discussed, the diagnostics procedure to diagnose arthritis doesn’t include a blood test. However, there are diagnostic tests that can be done to allow your vet to see if there is a presence of arthritis. 

One of those methods is to carry out radiographs of your dog’s joints that are affected. As you can see from the picture below, the picture on the left is that of a healthy knee joint in a dog. The one on the right is of a joint which is affected by arthritis.

The blue arrows in the image highlight the areas of the joint that are affected by arthritis. 

Treatment for arthritis can vary depending on the severity of the disease. Arthritis can be managed with a combination of medications prescribed by your vet (either oral or injection), as well as complimentary therapies such as physiotherapy and hydrotherapy. 

There is a type of treatment called non-steroidal anti-inflammatories (NSAIDs) which are the most common type of treatment for arthritis. Due to the way the medication interacts with the body it is often recommended that your dog’s kidney function is assessed every 6-12 months (again your vet can advise what is best for your dog).  

Due to the issues that may occur with your dogs mobility as a result of arthritis it is important that the weight of your dog is strictly controlled to help reduce the workload for the joints where possible. Hydrotherapy can be a great way to exercise your dog without putting too much strain on the joint but help keep them well exercised and maintain muscle mass (Stem Cell Vet, 2022). 

Final thoughts 

It’s so easy to become demotivated when your dog isn’t losing weight despite your best efforts. Hopefully this article has given you some insight into a few diseases that might affect your dog’s ability to lose weight. 

If you have any concerns about your pets health it’s important to get in touch with your registered vets and  book an appointment to speak with your vet and address any concerns that you may have. 

Did you find this article useful? Why not let us know your thoughts by sharing your review in our Facebook group! – Slimline Canine – Slim Solutions for overweight dogs


Blue Cross (2019) Cushing’s Disease in dogs:

Sandia Animal Clinic (2020) The importance of cortisol in cats and dogs:,medicine%20to%20treat%20several%20ailments

Southwind Animal Hospital (2022) Symptoms and Treatments for Hyperthyroidism in Dogs:

Washington State University – College of Veterinary Medicine (2021) Hypothyroidism in dogs: 

Animal Trust (2022) Arthritis is Dogs:,stiffen%2C%20swell%20and%20become%20painful

Stem Cell Vet (2022) Hydrotherapy for Canine Arthritis: 

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