Incidence, Risk Factors and Managing Obesity in Dogs and Cats

Main Image

Obesity is recognised as the most common form of malnutrition in Australian pets, with published national surveys having reported that 41% of dogs and 32% of cats in Australia are either overweight or obese.

Obesity is an important issue in pets as it can lead to a reduced quality of life for the pet, reduced enjoyment for the owner and it predisposes the dog or cat to a number of potentially serious illnesses. The major factor leading to obesity in pets is that the pet is eating more energy than it needs and in many cases, overweight pets get little exercise. Energy that is in the food that is excessive to the pet's underlying metabolic needs is stored as fat.

Read more or download a print friendly PDF file.

This info-bite should be read in conjunction with the PFIAA info-bite entitled:   Weight Management in Pets.


Deciding whether a pet is overweight can be a challenge for some owners and your veterinarian can assist by weighing your pet and determining your pet's body condition score. It is widely accepted that "Obesity" is a condition where the animal is 15% or more over its optimal body weight. If your pet is overweight, your vet can assist in modifying their diet and exercise routine to get them back into a healthy body condition and weight.

Incidence of pet obesity in Australian pets

A study to assess the incidence of obesity in dogs was undertaken in 2005. This included responses from 52 Australian Veterinary practices, providing information about 2661 dogs. Of these,33.5% were identified as being overweight and 7.6% as obese; with breed, gender and neutering identified as important factors 1.

In 2008, results of another survey exploring veterinarians' assessment of obesity in Australian cats was published. This report involved responses from 428 veterinary practices and the researchers analysed 973 cat reports from 48 veterinary clinics. This survey found that 33% of cats in the study were categorised as overweight or obese by veterinarians 2.

What causes pets to be overweight?

By far the most common contributing factors are overfeeding combined with too little exercise. When (food) energy intake (measured in kilojoules (kJ) or calories) exceeds the energy expended by the animal the excess energy eaten is stored as body fat in the dog or cat. This means that correcting excessive bodyweight and obesity in pets is largely reliant upon changing the type and / or how much food is provided to the pet and increasing the amount of energy burned by the animal through increased exercise.

Feeding practices and lifestyle factors are common contributing factor in many obese pets. These includes the frequency of feeding, leaving bowls of food available (ad-libitum feeding of excess food) when the pet is left unsupervised, the type and quantity of food offered ( e.g excessive table scraps). Neutering can also be a factor contributing to weight gain, because the hormonal changes associated with desexing means animals may require less energy in their diet. An indoor lifestyle and middle age are reported to be risk factors for obesity in dogs and cats.

Why pets overeat

  1. Owner feeding behaviour
    Many people enjoy seeing their pet eating and they can feel a little guilty about not being home all day to entertain the pet. As a result, some owners offer too much and/or inappropriate types of food to their pets. This can include feeding of high energy table scraps or excessive amount of "treats" particularly when more than one family member feeds treats and table scraps to the pet, so no-one takes charge of just how much (high energy) food the pet consumes each day.
  2. Boredom and emotional stress
    A recent study proposes that some pets overeat in response to stresses such as boredom, anxiety and depression. This might help to explain why some pets in a household seem to gain an extra kilo or two while others do not 3.
  3. Competition in multi-pet households
    Where there is more than one pet in a home, a dominant pet can develop, consuming more than their fair share and requirement.
  4. Hormonal influence
    Neutered / desexed pets have a tendency to gain weight as some owners continue to overfeed without recognising that their pets can have reduced energy requirements and insufficient exercise. Your vet can provide advice on the most appropriate amount and type of food for your pet.
  5. Medical conditions
    Some medications (e.g glucocorticoids) and medical conditions (e.g hypothyroid disease can contribute to excessive energy consumption relative to energy expenditure.

Pet health issues associated with being overweight:

Overweight pets may have a shorter lifespan and poorer quality of life as a wide range of medical conditions may affect obese dogs and cats more often than animals of normal body weight. It is important to realise that obesity is a common and preventable condition in the vast majority of cases and it can increase the risk to the health and quality of life of pets. Obesity is recognised to be associated with a number of medical issues including : 4, 5, 6, 7, 8:

  • Osteoarthritis
  • Cardiovascular disease
  • Insulin resistance / diabetes
  • Liver and pancreatic disease
  • Increased surgical risk
  • Heart disease
  • Reproductive disorders
  • Susceptibility to infection
  • Increased risk of some types of cancer

If you own an older overweight dog you may notice that he or she has a declining interest in going for a walk. This might be the first sign that your overweight dog is developing arthritis (joint inflammation) which can be exacerbated by the excessive weight which places increased stress and wear on their joints. We encourage you to seek veterinary advice and commit to managing their body weight and health.

Over feeding pets - a common issue

 (How much food should I feed my pet?)

It is important to understand how much food should be offered to your pet to provide for their energy needs. Foods vary dramatically in regards to how much energy (kJ) are provided per 100 g of food. For instance, dry food provides a lot more energy per 100g than the same weight of canned food, so much less weight of dry food is required to provide the equivalent amount of energy compared with canned foods. Feeding guides included on pet food packaging should be used as a guide only and owners are the best placed to assess their own pet's food needs and adjust the amount and type of food provided to suit the pet's breed/size, age, lifestyle, environmental conditions, body condition and level of exercise.  If the dog or cat is getting a bit "tubby", it means they are getting more kilojoules (calories) than they need, so less food can be offered, or perhaps offer the food only in set portion meals, rather than providing access to food all day.

How to assess dogs and cats for obesity

Pet owners can learn to assess the body condition of their dog or cat by feeling along the ribs, back and waist and to assess the pet's condition against a recognised body condition / weight guide chart. When viewed from above, dogs and cats should have a noticeable waist, between the end of the rib cage and the start of the hind quarters 9. When you run a hand over the pet's back and sides with light pressure, you should be able to feel both the spine and individual ribs. Your veterinarian can assist in helping you to assess your pet's body condition.

Your pet's ideal body condition

You can assess your pet's body condition by its appearance and by referring to weight charts for its breed and sex. The following examples of a body condition guides will help you to estimate your pet's body condition score.

If your pet has a body condition score of 7-9 (overweight - obesity) you can and should do something about it.

Weight control

If your pet is overweight (body condition score 7) or obese (body condition score 8/9), you should have it assessed by your vet. Prior to any weight loss program a thorough vet examination is recommended to check your pet's general health. Occasionally pathology tests such as a routine blood screen may be necessary to rule out underlying disease.

Your vet can give you an estimate of your pet's ideal body weight, and then calculate the amount of energy your pet needs to be fed each day until it reaches its target weight. Your vet may advise changes to your pet's diet or even prescribe a special veterinary diet if your pet is obese, and needs to achieve a significant weight loss (usually a target greater than 15% of its current bodyweight).

Achieving success is up to you and other members of your family. Only you can ensure that your pet really does lose weight. It will need effort and commitment, but is well worth it in terms of the extra quality of life, health and companionship your pet and you will enjoy. Feeding your pet a food that is "lighter" in energy content (kJ / calories) is a convenient and often effective way of keeping their calorie intake under control than simply giving less of their normal diet.


Achieving and maintaining a healthy body weight is not all about diet. Regular exercise is good for slimming animals as it increases the energy they burn. When used in conjunction with an energy- controlled diet, exercise helps the animal to shed those excess kilos faster. Getting your dog out for walks and runs are of obvious benefit for both you and your pet. Getting cats to exercise is generally tougher, but using your creativity to engage your cats in "object play", that mimics the cat's natural hunting instincts: chasing toys and playing with materials that encourage the cat to jump or follow vigorously will help entertain and exercise your cat. Cat scratch poles and dedicated "cat gyms" can all assist in increasing your cat's energy expenditure 10.

PFIAA resources for weight loss programs

A number of PFIAA member companies provide a variety of information and resources to assist veterinarians and owners to manage controlled weight loss in their pets. The PFIAA supports these initiatives and encourages all pet owners who are concerned about their pets' condition to visit these PFIAA members' websites and to seek veterinary advice to manage their pet's body condition and health.


1. The Veterinary Record, May 2005. P.D McGreevy, P.C Thomson, C.Pride, A. Fawcett, T.Grassi, B. Jones. "Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved".
2. McGreevy et al. "Overweight or obese cats presented to Aust. Veterinary practices: Risk factors and prevalence. Aust. Veterinary Practitioner 38 93):98-107.
3. Stress-induced and emotional eating in animals A review of the experimental evidence and implications for companion animals. Franklin D. McMillan, Journal of Veterinary Behaviour Vol 8, Issue 5, Sept 2013

4. Joshua, J.O. (1970). The obese dog and some clinical repercussions, J Sm Anim Pract, 11, 601- 606.
6. Williams, G.D. and Newberne, P.M.(1971). Decreased resistance to salmonella infection in obese dogs, Fed Proc, 30, 572.
7. Center, S.A.(1986). Feline liver disorders and their management, Comp Cont Ed, 8, 889-903.

8. Thornburg, L. P., Simpson, S. and Diglio, K. (1982). Fatty liver syndrome in cats. J Amer Hosp Assoc, 18, 397.The Veterinary Record, May 2005.
10. This article is for general information only This information is provided by the PFIAA as general information only. For advice and information concerning treatment and feeding your individual pet, we recommend that you seek the advice of your veterinarian.

This article is for general information only:
This information is provided by the PFIAA as general information only. For advice and information concerning feeding your individual pet, we recommend that you seek the advice of your veterinarian.