Overweight cats and dogs: checks, risks and safe weight loss

About this guideCompiled from the listed veterinary and health organisations’ guidance; not yet reviewed by a veterinarian.

General information for owners, not a substitute for examination, diagnosis or treatment by a veterinarian. If your animal seems very unwell, in pain, struggling to breathe or may have been poisoned, contact a vet immediately.

Quick answer

Key points

WSAVA body condition scoring (BCS) uses a 1–9 scale; 4–5 is ideal and anything above 5 is overweight.
At an ideal weight, the ribs are easy to feel under a slight fat covering and a waist is visible from above.
Obesity raises the risk of diabetes, arthritis, breathing problems, heat intolerance, anaesthetic complications and a shorter life.
Weight loss should be gradual and planned with your vet.
Never starve an overweight cat or cut its food drastically, because this can trigger a dangerous liver disease.

When should you see a vet?

Go to a vet immediately if an overweight cat stops eating, or if an overweight pet pants heavily, becomes very weak or collapses, especially in hot weather.
Ongoing weight gain together with coat changes, low energy or increased thirst.
Drinking and urinating much more, or losing weight despite a good appetite.
Limping, or reluctance to walk, jump or play.
Difficulty breathing or tiring quickly with exercise.
A cat that can no longer groom itself properly or develops skin problems.

Contact your nearest veterinarian or animal clinic. This site cannot assess your animal’s condition. Choosing a vet

In this guide (11)

When is a cat or dog overweight?

A cat or dog is overweight when it is 10–20% above its ideal weight, and obese when it is more than 20% above. This is the definition used by the Merck Veterinary Manual, which also calls obesity the most common nutritional problem in dogs and cats. Ideal weight varies with breed, age and build, so the number on the scale is often not enough on its own. Vets therefore use a body condition score (BCS) to judge how much body fat an animal carries. Cornell notes that many owners of obese cats do not recognise that their cat is obese, so regular checks really help.

Evidence: Merck Veterinary Manual — Nutrition in Disease Management in Small Animals ↗ · International Cat Care — Obesity in cats ↗ · Cornell Feline Health Center — How Often Should You Feed Your Cat? ↗

How does WSAVA body condition scoring work?

WSAVA uses a scale of 1 to 9: 1 is emaciated, 4–5 is ideal, and 6–9 ranges from overweight to severely obese. The score is judged by looking at and feeling the ribs, waist and belly. In an ideal dog, the ribs can be felt without excess fat, a waist is visible behind the ribs from above, and the belly is tucked up when seen from the side. In an ideal cat (score 5), the body is well proportioned, the ribs can be felt under a slight fat covering, the waist is visible but not pronounced, and the belly fat pad is minimal. WSAVA notes that a score of 6 may be acceptable in some cats, especially older cats.

From a score of 7 upwards, the ribs are hard or impossible to feel under fat, the waist disappears and the belly becomes rounded. Fat builds up over the lower back and base of the tail in dogs, and over the lower back, face and limbs in severely obese cats. The score measures fat, not muscle; WSAVA uses a separate muscle condition score because muscle can waste with disease or age. Ask your vet to show you how to score your own pet.

Evidence: WSAVA — Body Condition Score: Dogs ↗ · WSAVA — Body Condition Score: Cats ↗ · WSAVA Global Nutrition Committee — Frequently Asked Questions & Myths ↗ · WSAVA — Global Nutrition Guidelines and Nutrition Toolkit ↗

How can you check your pet's weight at home?

Feel the ribs, look for a waist from above, and check the belly from the side. The RSPCA says you should be able to feel a dog's ribs without excess fat, see a clear waist from above, and see the belly tucked up from the side. PDSA adds that the base of the tail should have no build-up of fat, and the spine and hip bones should be easy to feel but not stick out. In cats, the waist should be visible from above and the belly should not sag. Weigh your pet every week or two and record the results. Talk to your vet if the weight keeps going up or down, or if you are unsure.

Evidence: RSPCA — Pet Obesity: Causes, Treatment and Prevention ↗ · PDSA — Obesity in dogs ↗ · RSPCA Australia Knowledgebase — Do cats have special nutritional requirements? ↗

Why is obesity harmful to cats and dogs?

Obesity shortens life and lowers its quality. The Merck Veterinary Manual links it with arthritis, heart and breathing problems, weaker immunity, poor tolerance of heat and exercise, and higher risk during and after anaesthesia. In dogs, obesity is also linked with pancreatitis, cruciate ligament problems and heatstroke. In cats, it is associated with diabetes, lower urinary tract disease, skin problems and hepatic lipidosis (fatty liver disease). A Cornell study of more than 2,000 cats found that overweight cats were far more likely to develop diabetes and lameness, and obese cats were twice as likely to die in middle age. In hot weather, see also our guide to heatstroke in cats and dogs.

Evidence: Merck Veterinary Manual — Nutrition in Disease Management in Small Animals ↗ · PDSA — Obesity in dogs ↗ · International Cat Care — Obesity in cats ↗ · Cornell Feline Health Center — How Often Should You Feed Your Cat? ↗ · PDSA — Obesity in cats ↗ · Cornell Feline Health Center — Feline Diabetes ↗

What makes cats and dogs gain weight?

The most common cause is food and treats that supply more energy than the animal uses. Leaving food in the bowl all day leads many cats and dogs to overeat, and treats and human food add calories without owners noticing. International Cat Care explains that a cat's energy needs fall after neutering, and cats that are inactive or kept indoors are at greater risk. PDSA says neutering does not directly make dogs fat, but it can increase appetite and slow metabolism, so portions need adjusting. Diseases such as hypothyroidism and Cushing's disease, and some medicines such as steroids, can cause weight gain, although far less often than overeating and too little exercise.

Evidence: International Cat Care — Obesity in cats ↗ · PDSA — Obesity in dogs ↗ · Cornell Feline Health Center — Obesity ↗ · WSAVA Global Nutrition Committee — Frequently Asked Questions & Myths ↗

How can a pet lose weight safely?

Start with a veterinary check, then follow a weight-loss plan made for your pet. The vet will assess body condition, look for any disease that may be involved, set a target weight and choose a food. The Merck Veterinary Manual explains that simply feeding less of the usual food can cause nutrient deficiencies, so vets often choose a dedicated weight-loss diet. The most successful programmes combine controlled feeding with more activity, and regular weigh-ins so the plan can be adjusted. Weigh the food with kitchen scales, split it into several meals, and cut down on treats.

Never starve a cat or cut its food drastically without your vet's guidance. International Cat Care and Merck warn that losing weight too quickly can trigger hepatic lipidosis, a liver disease that can be fatal. The goal is slow, steady loss, and a very overweight cat may need up to a year to reach its ideal condition. If your cat refuses the chosen diet, tell your vet promptly so another option can be found, because a cat must keep eating enough every day.

Evidence: Merck Veterinary Manual — Nutrition in Disease Management in Small Animals ↗ · International Cat Care — Obesity in cats ↗ · PDSA — Obesity in dogs ↗ · Cornell Feline Health Center — Obesity ↗

How can you keep your pet at a healthy weight?

Feed measured portions, limit treats and keep your pet active every day. WSAVA advises that treats stay under 10% of daily calories and never replace a meal. Use the amount on the packet only as a starting point, then adjust it to body condition score, because every animal's needs differ. For cats, wand toys, balls and food puzzles help increase activity. For dogs, match the type and length of exercise to age, breed and health. Once the target weight is reached, keep weighing regularly at home or at the clinic, and make sure weight is checked at the yearly vet visit.

Evidence: WSAVA — Feeding treats to your dog ↗ · WSAVA — Feeding treats to your cat ↗ · WSAVA Global Nutrition Committee — Frequently Asked Questions & Myths ↗ · International Cat Care — Obesity in cats ↗ · PDSA — Obesity in dogs ↗ · PDSA — Obesity in cats ↗

Sources & references

References can change. Check dates and context in the original source.

Cite this page

PanduanHewan. (2026, 25 September). Overweight cats and dogs: checks, risks and safe weight loss. PanduanHewan.org. https://panduanhewan.org/en/pet-health/overweight-cats-and-dogs/

Overweight cats and dogs: checks, risks and safe weight loss

Key points

When should you see a vet?

When is a cat or dog overweight?

How does WSAVA body condition scoring work?

How can you check your pet's weight at home?

Why is obesity harmful to cats and dogs?

What makes cats and dogs gain weight?

How can a pet lose weight safely?

How can you keep your pet at a healthy weight?

Sources & references

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