Doggy NewsDoggy Training

7 common reasons why your dog may be struggling to lose weight


There are many health benefits to spaying or castrating your dog and I recommend this for the vast majority of my patients. You should be aware that neutering may influence to amount of calories your dog needs, by up to 20%. Reducing amounts given after surgery is advisable straightaway, to maintain a lean and healthy weight.

More recent research has linked changes with your dog’s behaviour after neutering, so they may become a bit more ‘foodie’. They might start finishing everything that is offered in the bowl and begin scavenging or begging for extras too. It means you may have to work harder to find ways to resist those pleading eyes.

Hormonal disease

Probably everyone who has an overweight dog thinks that their dog may have an under-active thyroid gland. About 1% of the dog population is thought to have an underactive thyroid, but there are estimates of over 50% of dogs being overweight, so the odds are still very low for it to affect your dog. There are other hormonal diseases, such as Cushing’s disease, that can also affect weight gain and your dog is at greater risk of developing diabetes if overweight.

If you are concerned, please ask your vet to run a routine blood screen to check for disease, before you start any significant changes to your routine. If nothing else it will put your mind at rest and you may well pick up a problem early, when it can be treated more effectively.

Change in exercise

We all know that after injury, or surgery, you may have to alter the distance or intensity of exercise your dog is doing. Have you considered altering their daily intake of food as well?

When dogs and cats are feeling unwell with a bug or after a bout of diarrhoea, they often alter the amount of food they are eating, especially if they are feeling lethargic. This allows time for their body to recover. Afterwards, their appetite improves, along with a return to normal exercise levels. However, if they are lame, the same effects their appetite and food consumed with not change naturally. Combined with the fact we may feel sorry for them and give them extra, or richer treats, the calories taken in can mount up.

It’s not just injuries to your dog that can have an effect. If you have an injury (or we enter a lockdown!) your dog will have a restriction on the amount of exercise they can do. Unless we account for this in their calorie intake, it’s very easy for the balance of energy to go awry. A dog is unable to lose weight unless they are in a negative energy balance.


As our pets age, they tend to have a lower metabolic rate, so will not need as much food. It is a combination of hormonal changes, some age related wear and tear on joints that leads to this slowing down as they age.

Older dogs, as people, find it more difficult to maintain muscle mass, especially if they are not exercising as much as they used to.

This is why senior foods are often lower calorie, with a proportionally higher level of good quality protein, that is easily absorbed to counteract these issues. Senior food would be suitable for any dog over the age of 7 years, but even if your dog is younger than this (and not still growing), a senior diet may provide an easy way to give a lower calorie food, that is just as beneficial. They will also often provide joint support supplements as standard within the diet.

Food label guides often use different calorie calculation factors for older dogs. On average older dogs will need less than younger dogs, even if their exercise is the same.


Pain can go un-noticed in any age of animal. Some especially stoic animals may have significant pain and limitations of movement, before the pain is recognized. I would recommend everyone to have a full, hands on assessment with your local veterinary surgeon, before embarking on a weight loss program.

Just like we ask humans to have a check over by their doctor for blood pressure and general health, your vet will be able to tell you if they find any reason that they should not exercise as normal. Pain can be insidious and often affect more than one joint, so just because your dog is not hopping lame, doesn’t mean they are not in pain.

Similarly, if your dog is limping, they will be feeling pain and discomfort somewhere, even if they are not crying out and willing to run on the other 3 legs!

Identifying and managing this pain, before starting to increase any exercise done, is vitally important. You may decide to include a low impact exercise, such as hydrotherapy, which provides buoyancy, along with greater resistance to build strength and muscle without the risk of further injury.

Your vet will be only too happy to support you and your dog onto the road to better health.

The good news is weight loss is the most effective treatment to manage the pain of long term osteoarthritis.


Many veterinary treatments have a brilliant effect to control a huge variety of diseases. Antibiotics to cure bacterial infections, steroids to control allergy and skin disease and seizure medications to control fits.

All of these (and others) can have a significant effect on your dog’s internal health. Even when given for a short amount of time, drugs can affect the microbiome. These are the small bugs living in your dog’s gut that help to digest different nutrients, to allow absorption and assimilation.

We are learning more all the time about how the microbiome is in a dynamic balance, which can be altered by medications, to make it more likely your dog might gain weight, or find it difficult to lose it.

We also know that certain medications alter our dog’s appetite, changing their behaviour, so they seek food more urgently, and consequently they can gain weight.

It’s not just food restriction, but being creative with how we feed our dogs, with enrichment of many types, that can help control this problem.

Feeding the wrong amount

Finally, feeding the wrong amount of food is one of the most common reasons why your dog is not losing weight. It is not enough to say ‘ But I’m feeding what the manufacturer recommends’.

In the small print of all dog food labels there should be the statement that says:

‘Feed to a lean and healthy bodyweight’

This means a body condition score of 4-5 out of 9 on the body condition score chart.
The food label guidelines give advice on the amount to feed to the average (unneutered) dog, doing the average amount of exercise, living the average life. Is your dog average? Every dog is a unique individual with unique needs and the guidelines may not be accurate for your dog.

If your dog is not losing weight on the amount you are currently feeding you have 3 options:

  1. Feed to same ‘quantity’ in grams, but switch diet to a lower calorie diet, so they will be taking in less calories overall. Prescription dog foods are suitable, which have a much lower calorie concentration, but still high in protein, and extra fibre to help your dog to feel full.
  2. Reduce the amount of food again by 10% and monitor weight every 2 weeks, and reduce again by 10% if still no effect, until you are getting a safe amount of weight loss each week.
  3. Calculate the number of calories they actually need and work out the number of grams of dog food that should be for your dog. Adjust again, if your dog is not losing weight on that amount.

After reading about these 7 common reasons why your dog might not be losing weight, you will see why it is not always easy for your dog to reach their target weight.

What is the biggest challenge for your dog?

Have you ruled out all of these factors?

By Dr Caroline – The Slim Pet Vet

Slimline Canine – Slim Solutions for Overweight Dogs