Is your dog overweight? It is the most common health problem in pet dogs, and the hardest for owners to see — because weight creeps up slowly, because a round dog looks happy and well-fed, and because the scales only tell part of the story. This guide covers the signs of an overweight dog, how to check body condition at home, what causes weight gain, and a practical diet plan to bring weight down safely. It is a plan for a healthy dog that has simply eaten too much and moved too little; if your dog has a health condition, or has lost weight without explanation, see a vet first.
The scale of the problem is worth stating plainly. Vets report that a large share of the dogs they see are overweight, and owners routinely underestimate it: most owners of an overweight dog think the dog is about right. That is why the checks below matter more than a guess — they take a minute, they are free, and they are more reliable than looking at the dog and hoping.
Signs your dog is overweight
The most reliable sign is the ribs: you should be able to feel them easily under a thin layer of fat, without pressing hard. If you have to press to find them, or cannot feel them at all, the dog is overweight. The second sign is the waist: look from above, and there should be a visible waist behind the ribs. If the body is straight or bulges out, the dog is overweight. The third sign is the tummy: look from the side, and the belly should tuck up behind the ribs. If it hangs level or sags, the dog is overweight. The fourth sign is behaviour: a dog that pants quickly on a short walk, struggles with stairs, is slow to get up after rest, or has stopped playing as much may be carrying too much weight — though these can also be signs of other problems, so mention them to your vet.
Other signs are easier to miss. A collar that needs letting out, a harness that fits tighter than it did, a dog that begs more because it is fed less at meals but given more treats, and a vet that mentions weight at every visit — all of these are worth taking seriously. Weigh the dog monthly and keep a note: a kilogram a month is a slow drift that is easy to miss and easy to fix, while five kilograms is a problem that takes months to undo. Vets score body condition on a 9-point scale, where 4–5 is ideal, below 4 is too thin, and above 5 is overweight; ask your vet to score your dog and show you what ideal feels like.
What causes weight gain in dogs
The cause is almost always the same: more calories in than out, sustained over months. The extra calories usually come from three places. First, food: the daily amount is guessed rather than measured, the bag's generous feeding chart is treated as a target, or the dog is fed a puppy food long after it has stopped growing. Second, treats: a biscuit here, a piece of cheese there, and the dog's daily calories rise by a quarter without anyone noticing — treats should stay under 10% of daily calories. Third, table scraps, which are often fatty and calorie-dense and which teach begging.
On the other side, exercise often drops without anyone noticing: a puppy that was walked three times a day becomes an adult that is walked once, or a dog that used to run in a garden moves to a flat with a short pavement walk. Neutering lowers calorie needs by about 10–20%, so a dog that eats the same amount after neutering will gain weight. Age lowers calorie needs too: a senior dog that eats the same as it did at five will gain weight by eight. And some medical conditions and medicines cause weight gain, which is another reason to see a vet before starting a diet plan — a diet will not fix a thyroid problem.
The overweight dog diet plan
Start by getting a target weight from your vet — a number based on your dog's breed, size, and body condition, not a guess. Then work out the food for that target weight, not the current weight. Use the RER formula: RER = 70 × (target weight in kg)^0.75, multiplied by about 1.0 to 1.2 for weight loss. For example, a dog with a target weight of 25 kg has an RER of about 784 calories, so it needs about 785 to 940 calories a day while losing weight. A dog with a target weight of 10 kg has an RER of about 394 calories, so it needs about 395 to 475 calories a day. A dog with a target weight of 40 kg has an RER of about 1,107 calories, so it needs about 1,110 to 1,330 calories a day.
Feed a complete and balanced food — a weight-management or light food can help, because it is lower in calories and higher in fibre, so the dog feels fuller on fewer calories — and measure it with scales, every meal, every day. Split the daily amount into two meals, morning and evening. Cut treats to under 10% of daily calories, and use part of the daily food ration as training rewards instead of extra biscuits. Stop table scraps entirely. If there are several people in the house, agree who feeds the dog and how much — the most common cause of a failed diet is one person giving extras that nobody else knows about.
Aim for a slow loss of about 1–2% of body weight per month: a 30 kg dog should lose about 0.3–0.6 kg a month, a 10 kg dog about 0.1–0.2 kg. Faster loss is not better and can be unhealthy, especially for a dog that is very overweight. Weigh monthly, on the same scales, and adjust food by about 10% if weight is not moving after a month. If weight is not moving at all, check the extras first — treats, scraps, and a second feeder — before cutting the main meals further. The dog calorie calculator works out the numbers from your dog's target weight, and the dog food calculator converts them into cups and grams.
Exercise for an overweight dog
Exercise should increase gradually, not suddenly. A dog that is overweight and unfit should start with short, regular walks — ten to fifteen minutes, twice a day — and build up over weeks as fitness improves, rather than a sudden long hike that strains stiff joints. Swimming is excellent for overweight dogs because it exercises without loading the joints, if the dog likes water and the vet approves. Play, scent games, and training all count as activity, and they keep the dog engaged without adding calories.
Avoid high-impact exercise until the dog is fitter: no jumping, no running on hard surfaces, and no long runs. Watch for panting, lagging behind, or stiffness the next day, and cut back if any of those appear. And remember that exercise alone will not fix weight — a dog cannot outrun a bowl that is too full. Food is the lever that moves weight; exercise is the lever that keeps muscle, joints, and mood healthy while the weight comes off. The exercise needs calculator gives daily exercise minutes by breed, age, and energy level.
When to see a vet
See a vet before starting a diet plan if your dog has any health condition, takes medicine, is a puppy or a senior, or has lost weight without explanation. See a vet promptly if the dog is very overweight, has difficulty breathing, cannot exercise at all, or has a swollen belly. And see a vet if the diet is not working after two months of measured food and regular exercise — there may be a medical cause, or the target weight may need revising. A vet visit is also the best place to get an accurate weight, a body condition score, and a target weight that everyone in the house can work towards.
For related reading, see the dog ideal weight calculator, the dog calorie calculator, the dog food calculator, the exercise needs calculator, the how much should my dog weigh guide, the senior dog diet guide.
Frequently asked questions
How do I know if my dog is overweight?
Feel the ribs — you should feel them easily under a thin layer of fat. Look from above for a waist behind the ribs, and from the side for a tummy tuck. If you cannot feel the ribs or there is no waist, the dog is probably overweight. Your vet can confirm with a body condition score.
How much should I feed an overweight dog?
Work out food for the target weight, not the current weight: RER × 1.0 to 1.2. A dog with a target weight of 25 kg needs about 785 to 940 calories a day. Measure food with scales, split it into two meals, and keep treats under 10% of daily calories.
How fast should my dog lose weight?
About 1–2% of body weight per month — about 0.3–0.6 kg a month for a 30 kg dog. Faster loss is not better. Weigh monthly and adjust food by about 10% if weight is not moving.
Should I exercise my overweight dog more?
Yes, but gradually. Start with short, regular walks and build up over weeks. Swimming is excellent because it does not load the joints. Avoid jumping and running on hard surfaces until the dog is fitter.
Why is my dog gaining weight?
Usually more calories in than out, sustained over months: food guessed rather than measured, treats creeping up, table scraps, less exercise, and lower calorie needs after neutering or with age. Some medical conditions cause weight gain, so see a vet before starting a diet plan.
Is my dog overweight or just big?
Size and fat are different things. A big dog of a large breed can be lean at 35 kg, and a small dog can be overweight at 12 kg. Body condition — ribs, waist, and tummy tuck — is the check that tells them apart, not the number on the scales alone.
Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.