How do you help a dog lose weight safely? Slowly, with measured food, a little more exercise, and a monthly weigh-in — not with a crash diet, not with a sudden large cut in food, and not with a food change every few weeks. This guide is the full plan: how many calories a dog that needs to lose weight should eat, how fast weight should come off, how to build exercise up safely, and the mistakes that make weight loss fail. Every figure is an estimate, and a dog that needs to lose a lot of weight should have a plan set with its vet — especially a cat, where rapid weight loss can cause a serious liver problem.
The short version is: feed a measured amount of a complete and balanced food, cut food by about 10% at a time, keep treats under 10% of daily calories, and aim for slow, steady loss — about 1% of body weight per month. Weigh the dog monthly, and if weight is not moving after a month, cut food by about 10% again and re-weigh in another month. A dog that loses weight slowly and keeps it off is a success; a dog that loses weight fast and puts it straight back on is not. The dog weight loss diet plan guide puts food and exercise together into a week-by-week plan, and the best food for overweight dogs guide explains how a weight-loss food differs from a normal food.
How many calories should a dog lose weight on?
Start with the resting energy requirement, or RER — the calories a dog burns at rest. The formula vets use is: RER equals 70 times body weight in kg to the power of 0.75. A typical neutered adult dog needs about 1.6 times its RER, and a dog that needs to lose weight usually needs about 1.1 times its RER as a starting point — less than maintenance, but not a crash diet. The table below gives the daily calories for a dog at different weights, at the normal adult factor and at the weight-loss target. Use the row nearest the dog's current weight.
| Body weight | Normal adult calories | Weight-loss calories (target) |
|---|---|---|
| 5 kg | 375 | 255 |
| 10 kg | 630 | 435 |
| 20 kg | 1060 | 730 |
| 30 kg | 1435 | 985 |
| 40 kg | 1780 | 1225 |
If weight is not moving after a month, cut food by about 10% and re-weigh in another month. If weight is falling faster than about 1% of body weight per month, feed a little more — fast weight loss loses muscle as well as fat, and in cats it can cause a serious liver problem, so slow is safe. Note that calories are the real target and cups are only a translation: different foods have very different calorie densities, so always check the kcal per cup or per 100 g on your own bag or tin and work from that. The dog calorie calculator works out the same figures for any weight, and the how many calories to lose weight for dogs guide gives the full tables.
How fast should a dog lose weight?
Slowly. A commonly cited safe target is about 1% of body weight per month, which means a 20 kg dog losing about 200 g a month and a 5 kg cat losing about 25 to 50 g a month. That sounds slow, and it is — but slow weight loss is the kind that stays off, because it gives the dog time to adjust, keeps muscle, and does not leave the dog hungry and miserable. A dog that loses weight faster than that is losing muscle as well as fat, and a cat that loses weight fast can develop a serious liver problem called hepatic lipidosis, which is a veterinary emergency. If your dog is losing weight faster than the target, feed a little more and mention it to your vet.
Weigh the dog monthly, at the same time of day, on the same scales, and write the number down — the line over months is what matters, not any single reading. Feel the ribs at every weigh-in too: you should be able to feel them easily under a thin layer of fat, and see a waist from above and from the side. A dog that is losing weight but still has no waist is still overweight, and a dog whose ribs are easy to see and whose waist is very obvious may have gone too far. The how to weigh your dog at home guide explains the bathroom-scale method, and the dog body condition score chart shows the nine-point scale vets use.
Food: what to feed and how to feed it
Feed a complete and balanced food made for weight loss, or feed less of the normal food with your vet's agreement. A weight-loss food is a normal food with fewer calories per mouthful — less fat, more fibre, and enough protein to hold muscle while weight comes off. Less fat matters because fat carries more than twice the calories of protein or carbohydrate per gram; more fibre matters because fibre adds bulk without calories, so the dog feels full on fewer calories; more protein matters because a dog losing weight loses muscle as well as fat unless its protein intake stays good. Check the kcal per 100 g on the label rather than the word 'light' on the bag.
Split the daily amount into two meals a day for an adult dog — morning and evening — rather than one large meal, because two smaller meals are easier on digestion and keep the dog feeling fed through the day. Measure food with scales or a measuring cup, not a mug or a handful: a mug of dry food can carry a quarter more calories than a measured cup, and that quarter is often the whole difference between losing weight and not losing it. Keep treats under 10% of daily calories, and count them — use the dog's own food as treats, or a single low-calorie treat. The free feeding vs scheduled feeding for dogs guide explains why leaving food down all day makes weight loss almost impossible.
Exercise: building it up safely
Food is most of weight loss, but exercise matters too, because it keeps muscle, burns calories, and keeps the dog happy. An overweight dog should build exercise up gradually — short, frequent walks or play sessions rather than one long weekend hike, because a heavy dog that is suddenly asked to run will strain its joints. Start with what the dog can do comfortably, add a little each week, and watch for stiffness or tiredness the next day: a dog that is stiff the day after exercise has done too much, and the next session should be shorter.
For dogs, walking is the safest start: two or three short walks a day, on flat ground, building up the time over weeks. Swimming is excellent for an overweight dog, because the water takes the weight off the joints — but only where the dog is safe and supervised, and only if the dog is comfortable in water. For cats, play is the exercise: short, frequent play sessions with a toy the cat can chase and catch, a scratching post, and climbing places. The best exercise for overweight dogs guide gives a safe build-up plan, and the exercise needs calculator puts exercise in the context of age and size.
Mistakes that make weight loss fail
The most common mistake is guessing the amount: a dog fed by eye is almost always fed too much, because a mug or a handful is not a measure. The second is forgetting treats: treats, table scraps, and food from other pets' bowls all count, and they often add up to more than the meal itself. The third is changing food every few weeks: a weight-loss plan needs at least two months before it can be judged, and a food changed after two weeks has not had a fair trial. The fourth is cutting food too fast: a crash diet loses muscle, leaves the dog hungry and miserable, and in cats can cause a serious liver problem.
The fifth is giving up after a plateau: weight loss is rarely a straight line, and a month with no change is normal — cut food by about 10% and keep going, rather than abandoning the plan. The sixth is forgetting that everyone in the house must follow the plan: a dog fed by three people is fed three times, so agree together who feeds the dog and what treats are allowed. The seventh is stopping when the target is reached and going back to the old amount: a dog that has lost weight needs less food than it did before, because a lighter dog burns fewer calories — keep the food measured and the weigh-ins monthly for life. The dog weight loss diet plan guide covers the maintenance stage as well as the loss stage.
For related reading, see the dog weight loss diet plan guide, the best food for overweight dogs guide, the how many calories to lose weight for dogs guide, the best exercise for overweight dogs guide, the dog ideal weight calculator, the dog body condition score chart.
Frequently asked questions
How do I help my dog lose weight safely?
Slowly, with measured food, a little more exercise, and a monthly weigh-in. Cut food by about 10% at a time, keep treats under 10% of daily calories, and aim for about 1% of body weight per month. A dog that loses weight slowly and keeps it off is a success; a dog that loses weight fast and puts it straight back on is not. See a vet before starting if the dog needs to lose a lot of weight.
How many calories should my dog eat to lose weight?
As a starting point, about 1.1 times its resting energy requirement (RER), where RER equals 70 times body weight in kg to the power of 0.75. A dog of 10 kg needs about 435 calories a day to lose weight, against about 630 at normal maintenance. Adjust by monthly weigh-ins.
How fast should my dog lose weight?
A commonly cited safe target is about 1% of body weight per month. That sounds slow, and it is — but slow weight loss is the kind that stays off, and fast weight loss loses muscle as well as fat. In cats, rapid weight loss can cause a serious liver problem, so slow is especially important for cats.
Should I use a weight-loss food?
A weight-loss food helps, because it carries fewer calories per mouthful, less fat, more fibre so the dog feels full, and enough protein to hold muscle. But feeding less of a normal complete and balanced food also works, with your vet's agreement, as long as the amount is measured and the dog is weighed monthly. Check the kcal per 100 g on the label, not the word 'light' on the bag.
How much exercise does an overweight dog need?
Build it up gradually — short, frequent walks or play sessions rather than one long weekend hike, because a heavy dog that is suddenly asked to run will strain its joints. Start with what the dog can do comfortably, add a little each week, and watch for stiffness or tiredness the next day.
What if my dog's weight stops falling?
A plateau is normal — weight loss is rarely a straight line. Cut food by about 10% and keep going for another month, rather than abandoning the plan. If weight still does not move after two months, or if the dog is lethargic or off its food, see a vet.
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.