Incidence, Risk Factors and Managing Obesity in Dogs and Cats

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 several 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. Put simply, it is a case of too many calories in and not enough calories being used throughout the day.  

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 recommending a specific low-calorie  diet, controlled rations and an appropriate exercise routine to get them back to 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. This means that correcting excessive bodyweight and obesity in pets is largely reliant upon portion controlling the food provided to the pet and increasing exercise or activity throughout the day. 

There are also a series of pet and owner related factors that can contribute to obesity in cats and dogs. The way we feed our pets can be very important – for example, allowing our pets uncontrolled access to food all day (i.e. ad libitum feeding) increases the risk of overeating. Additionally, when we treat them regularly with table scraps or treats, the extra calories from these foods are very likely to add to the pet’s waistline over time. 

Some factors associated with the pet’s metabolism, genetic make-up and age can also play a role. Neutering is a known risk factor for weight gain, as the hormonal changes associated with de-sexing alters the metabolism of the animal, meaning they require approximately one third  less energy in their diet daily. Other risk factors include an indoor, sedentary lifestyle, being middle aged and certain breeds appear over-represented too.

Why pets overeat

1.Owner feeding behaviour
Many people bond with their pet through food and enjoy seeing their pet eating. With our busy lifestyles, many use foods as a means of making up for the long hours we leave our pets alone throughout the day. 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 number of “treats”. This becomes a bigger issue  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. It is important to work with your veterinarian to find ways to help alleviate these issues in other ways, such as enriching the pets home environment.

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/de-sexed 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 are more likely to 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. 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
  • Increased susceptibility to infection
  • Increased risk of some types of cancer

Weight control

If your pet is overweight (body condition score 6/7) 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 laboratory 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. It will be a combined 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 a calorie- controlled diet, exercise helps the animal to shed those excess kilos faster. Taking your dog out for walks and runs are of obvious benefit for both you and your pet. Getting cats to exercise requires a bit more imagination., Engage your cats in “object play”, that mimics the cat’s natural hunting instincts such as chasing toys and playing with materials that encourage the cat to jump or follow vigorously. This will help entertain and exercise your cat. Cat scratch poles and dedicated “cat gyms” can all assist in increasing your cat’s energy expenditure9. 

There are also a great assortment of interactive feeders your pets can enjoy without you. These toys encourage your cat or dog to forage for their food and are a great way to encourage activity and provide mental stimulation.

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.
5. Williams, G.D. and Newberne, P.M.(1971). Decreased resistance to salmonella infection in obese dogs, Fed Proc, 30, 572.
6. Center, S.A.(1986). Feline liver disorders and their management, Comp Cont Ed, 8, 889-903.
7. 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.
9. 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.