By Dr. Anne Quain, a companion animal veterinarian and senior lecturer at the Sydney School of Veterinary Science. Her research interests include veterinary general practice and ethical challenges in the veterinary sector.
As a general practice veterinarian, I see many dogs and cats who are overweight or obese.
While our pets aren’t self-conscious about their appearance, excess weight can negatively impact both their quality and quantity of life.
Understanding Pet Weight: Are They Overweight or Obese?
According
to the Global Pet Obesity Initiative, animals that are obese are 30% or more
above their ideal body weight [1].
But ideal body weight isn’t easily defined by a number – especially in dogs,
where there is huge variation in body size between and even within breeds.
Veterinarians assess pet weight status using a five- or
nine-point Body Condition Score (BCS). The nine-point condition score is emerging as
the preferred option, so I will refer to that in this discussion. According to
this score, every category between over 5 represents about 10% excess body
weight. That means that a body condition score of 9 indicates that an animal is
40% above their ideal weight [2].
Animals with a body condition score of 6 or 7 are overweight, and those with a
body condition score of 8 or nine (or more – and I do see them from time to
time) are obese.
One of the challenges regarding overweight and obese animals is that many owners don’t recognise the problem unless it is pointed out. Researchers have called this “weight blindness”[3].
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| Credit: Association for Pet Obesity Prevention |
This involves looking at their overall body condition, how easy (or challenging) it is to feel their ribs, whether they have a visible waist when looked at from above, and whether they have a visible “tummy tuck” when looked at side on [see links to the scoring charts at the end of this article].
Another challenge is that veterinarians might not mention
that an animal is overweight. This is particularly the case where animals are
taken to the vet for another problem – for example, vomiting or diarrhoea. Your
veterinarian may be preoccupied with the reason you’ve brought the animal to
see them. It’s always helpful to ask your vet about your pet’s body condition
score.
How common is obesity?
In Australia, the prevalence of obesity in dogs was 7.5%, but 33.5% were overweight [4].
Obesity affected about 6.6% of cats, but a further 26.2% were overweight [5]. A very large study from the US involving almost 5 million dogs and almost 1.5 million cats reported that obesity affected 8.4% of adult dogs and 13.9% of adult cats, with rates increasing in mature and senior pets [6]. This isn’t surprising, as the metabolism of animals slows down with age – as it does in people. This makes them more prone to weight gain.
These numbers echo my experience as a veterinarian in
Australia. Around one in 20 pets I see are obese, but a larger proportion are
overweight.
The Root Causes of Weight Gain in Pets
The key driver of obesity is what is known as having a
“chronic positive energy balance” – that is, regularly taking in more calories
than are used. While there are some medical conditions that cause excessive
weight gain in animals, the most common cause of obesity in pets is us. That
is, humans providing animals with access to food that exceeds their energy
requirements. That additional energy is stored as fat or adipose tissue.
Other contributing factors include:
- Genetics: Some breeds, like Labradors [7, 8], have a genetic predisposition to weight gain and a higher food drive. The jury is out on how and to what degree desexing might impact weight. It is likely that diet and lifestyle have a greater impact.
- Lifestyle: Many pets lead a sedentary life. For example, indoor cats and dogs whose owners are too busy for long walks often don't get the physical activity they need. Daily play sessions for cats and regular walks for dogs are vital for both their mental and physical health. They don’t have to be long – just regular.
- Treats and Guilt: Feeding too many high-calorie treats, whether out of love or guilt for not exercising them enough, is a major contributor. Remember, there are other ways to show your pet love, like giving them your attention and time.
- Medications: Certain medications, such as those for seizures or steroids, can increase a pet's appetite. Hiding medication in high-fat treats can also add extra calories. And yes, some animals are extremely adept to helping themselves to unattended or unauthorised snacks (including meals intended for other household pets), or persuading one household member that another household member forgot to feed them.
The Health Risks of Extra Weight
Obesity isn't just about appearance; it has serious health consequences. It affects pets in two key ways:
- Reduced Quality of Life: Excess weight can lead to or worsen other conditions. For example, owners of overweight and obese cats were twice as likely to report early signs of arthritis than owners of cats that were not overweight [9].
- Shorter Lifespan: studies suggest that obesity reduces the overall lifespan of affected animals, and is associated with increased risk of sudden death [10] [11, 12].
The evidence suggests that pets with an ideal body condition will live longer, healthier, happier lives.
The treatment for obesity is straightforward: reduce caloric intake and increase caloric output [13].
It is important to remember that animals should not be starved or put on “crash” diets as this can make them extremely ill.
And there are some challenges. Recent studies suggest that even where veterinary supervision is provided, animals put on diets gained rather than lost weight [14, 15]! How could this be?
Humans, like the animals we live with, tend to be creatures of habit. Many owners feed animals treats between meals, and feel guilty withholding these. And their pets let them know that they’ve forgotten to give their usual treat!
In devising a diet, it is important to know exactly what an animal is fed, and what they eat – which might include some items that they aren’t intentionally fed by their owners. In some cases, providing lower calorie treats may be more achievable than cutting out treats altogether. (As an aside, I am currently leading a small research team investigating what dogs are fed, and what they eat, between meals).
Your veterinarian may be able to recommend other strategies, such as providing bulkier, low-calorie foods so that animals fed a lower calorie diet don’t feel they are getting less.
Providing consistent, regular exercise is also important.
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| Dr Anne Quain's family dog Tanner enjoys some low-impact exercise in a local creek. |
What About Weight Loss Drugs for Pets?
Weight loss drugs like Ozempic have been used widely by humans, so it is no surprise that similar drugs have been developed for pets.
However, many owners were concerned about side effects, which included vomiting, diarrhoea and lethargy. Additionally, one of the affects of the drug – reduced appetite – didn’t go down well. Some owners felt this negatively impacted their bond with their dog. Another concern is that medication that leads to reduction of appetite can make it hard to tell whether an animal is unwell. This is because a common sign of illness in pets is loss of normal appetite.
Essential Tips for Pet Owners
✔️ Be Aware: Make a habit of weighing your pet at every vet visit and performing a body condition score check at home.
✔️ Measure Food: Don't eyeball it! Use a measuring cup or kitchen scale to ensure you're feeding a consistent and accurate amount of food.
✔️ Track Everything: Keep a food diary to account for all calories, including treats and scavenged snacks. This helps you and your vet create an accurate weight loss plan.
✔️ Consult Your Vet: Always talk to your veterinarian about creating a safe and effective weight loss plan tailored to your pet. Avoid crash diets, as they can be dangerous.
Body Condition Score chart for dogs: https://wsava.org/wp-content/uploads/2020/01/Body-Condition-Score-Dog.pdf
Dr Anne Quain is a companion animal veterinarian and senior lecturer at the Sydney School of Veterinary Science.
1. Ward, E., A.J. German, and J.A. Churchill. The Global Pet Obesity Initiation Position Statement. 2019 [cited 2025 27.5.2025]; Available from:
https://www.petobesityprevention.org/global-pet-obesity-initiative.
2. Broome, H.A.O., et al., Weight loss outcomes are generally worse for dogs and cats with class II obesity, defined as 40% overweight. Scientific Reports, 2023. 13(1): p. 22958.
3. Gille, S., et al., Dog Owners' Perceptions of Canine Body Composition and Effect of Standardized Education for Dog Owners on Body Condition Assessment of Their Own Dogs. Vet Sci, 2023. 10(7).
4. McGreevy, P.D., et al., Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved. Vet Rec, 2005. 156(22): p.695-702.
5. McGreevy, P., et al., Overweight or obese cats presented to Australian veterinary practices: risk factors and prevalence. Australian Veterinary Practitioner, 2008. 38(3): p. 98-107.
6. Montoya, M., et al., Overweight and obese body condition in ∼4.9 million dogs and ∼1.3 million cats seen at primary practices across the USA: Prevalences by life stage from early growth to senior. Preventive Veterinary Medicine, 2025. 235: p. 106398.
7. Raffan, E., et al., A Deletion in the Canine POMC Gene Is Associated with Weight and Appetite in Obesity-Prone Labrador Retriever Dogs. Cell Metab, 2016. 23(5): p. 893-900.
8. Wallis, N. and E. Raffan, The Genetic Basis of Obesity and Related Metabolic Diseases in Humans and Companion Animals. Genes, 2020. 11(11): p. 1378.
9. Maniaki, E., et al., Associations between early neutering, obesity, outdoor access, trauma and feline degenerative joint disease. Journal of Feline Medicine and Surgery, 2021. 23(10): p. 965-975.
10. Kealy, R.D., et al., Effects of diet restriction on life span and age-related changes in dogs. Journal of the American Veterinary Medical Association, 2002. 220(9): p. 1315-1320.
11. Salt, C., et al., Association between life span and body condition in neutered client-owned dogs. Journal of Veterinary Internal Medicine, 2019. 33(1): p. 89-99.
12. Teng, K.T., et al., Strong associations of nine-point body condition scoring with survival and lifespan in cats. Journal of Feline Medicine and Surgery, 2018. 20(12): p. 1110-1118.
13. Shepherd, M., Canine and Feline Obesity Management. Veterinary Clinics: Small Animal Practice, 2021. 51(3): p. 653-667.
14. Porsani, M.Y.H., et al., Factors associated with failure of dog's weight loss programmes. Vet Med Sci, 2020. 6(3): p. 299-305.
15. Haddad, K.K., How Successful Are Veterinary Weight Management Plans for Canine Patients Experiencing Poor Welfare Due to Being Overweight and Obese? Animals (Basel), 2024. 14(5).
16. Henning, J., et al., Cats just want to have fun: Associations between play and welfare in domestic cats. Anim Welf, 2023. 32: p. e9.
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