How Much Should I Feed My Cat to Lose Weight? A Safe Plan

A cat diet needs less food than you might guess, but not as little as you might be tempted to try. Cats are the one pet where crash dieting is truly dangerous: a cat that eats too little for too long can develop fatty liver disease. The safe approach is a measured calorie target, a slow pace and regular weigh-ins. Here’s how vets set it up, with a worked example from our cat calorie calculator.

How many calories should a cat eat to lose weight?

The 2014 AAHA Weight Management Guidelines give two starting points:

Method	How it works	When it fits
80% of RER at ideal weight	Work out resting energy needs (RER) for the cat’s goal weight, then take 80%	You don’t know exactly what the cat eats now
80% of current intake	Measure everything the cat eats for a week or two, then cut it to 80%	You’ve been weighing food carefully

RER is the energy a cat needs at rest: 70 × (body weight in kg)^0.75. Our post on how many calories a cat needs explains it in plain terms.

The same guidelines set the target pace for cats at 0.5% to 2% of body weight a week, with a recheck every 2 weeks until the rate is steady, then monthly. The review by Hoelmkjaer and Bjornvad adds a protein floor of at least 5 grams per kg of target weight per day, so the cat loses fat, not muscle. That’s one reason vets often suggest a weight-loss food: it keeps protein up while calories come down.

Worked example: a 16 lb cat with a 12 lb goal

Put a 16 lb neutered cat with an ideal weight of 12 lb into the cat calorie calculator in weight-loss mode. It gives about 200 kcal a day (range 180 to 220), with no more than 20 kcal of that from treats.

For context, the calculator puts the same cat’s maintenance needs at about 370 kcal at 16 lb and about 300 kcal once it reaches 12 lb. So the diet is roughly half of what this cat was probably eating, and that’s why measuring matters. The protein floor works out to about 27 grams of protein a day for a 12 lb (5.4 kg) target.

Next, the cat food calculator turns 200 kcal into food. Using a wet food with 90 kcal per can and a dry food with 400 kcal per cup (3,800 kcal/kg):

Feeding style	Daily amount for 200 kcal
All wet	About 2¼ cans
Half wet, half dry	About 1⅛ cans + ¼ cup dry (26 g)
All dry	About ½ cup (53 g)

Your foods will have different calorie counts, so plug in the numbers from your labels. For more on mixing wet and dry, see our guide to how much wet food to feed a cat.

How long will it take my cat to lose weight?

Here’s the 16 lb cat again, losing a percentage of its current weight each week:

Weekly loss	Pounds per week at the start	Weeks to reach 12 lb (about)
0.5%	0.08 lb (1.3 oz)	58
1%	0.16 lb (2.6 oz)	29
2%	0.32 lb (5.1 oz)	15

That’s months, not weeks, and it lines up with Hoelmkjaer and Bjornvad’s estimate of 24 to 60 weeks for a cat losing 3 kg. A kitchen or baby scale that reads in ounces makes weekly weigh-ins much more useful than a bathroom scale.

Why measuring cups let cat diets down

Hoelmkjaer and Bjornvad report that measuring cups were off by anywhere from 18% too little to 80% too much, and small portions, like a cat’s, were the worst. At 200 kcal a day, an 80% overpour of the dry portion in the all-dry example adds about 160 kcal, which wipes out the diet. Weigh dry food in grams. AAHA recommends the same.

Other common reasons a cat diet stalls:

• Another person in the house feeding extra.
• Eating the dog’s food or another cat’s food.
• Treats and table scraps not counted. AAHA says treats should be no more than 10% of daily calories.

If the cat isn’t losing after a few weeks, the review suggests adjusting by about 10% at a recheck, not making a big cut.

What happens if a cat loses weight too fast?

Fatty liver disease, or hepatic lipidosis. Cornell’s feline health center says it is almost always preceded by a cat refusing food, and it seems much more common in obese cats. Cornell also notes it is fatal if not treated promptly. In the obesity review, a cat restricted to 60% of its maintenance calories developed the disease.

That’s why AAHA says a cat shouldn’t go longer than 24 hours without eating, and why any diet change should be gradual. Offer the new food alongside the old one at first rather than swapping overnight.

How can I help my cat feel full and stay active?

• Split the day’s food into 3 or 4 small meals.
• Use food puzzles or treat balls for part of the dry portion.
• Move the bowl upstairs or to a different room so your cat walks to eat.
• Play for a few minutes, two or three times a day, with a wand toy.

Keeping it off matters too. Hoelmkjaer and Bjornvad note that 46% of cats in one study regained weight after a diet. Once your cat reaches its goal, switch to maintenance calories for the new weight and keep weighing monthly. Our post on how much a cat should weigh shows how to check body condition at home.

Is a cat diet different from a dog diet?

Yes, in one important way. AAHA’s target for dogs is a little faster, about 1% to 2% a week. Cats get a gentler range, and the 24-hour limit on going without food is specific to them. For the dog side, see how fast a dog should lose weight.

Why the plan starts at 80%

I set the weight-loss mode of the cat calorie calculator to 80% of resting calories at the ideal weight because that’s the 2014 AAHA starting point, and I chose not to go lower: with cats, a too-aggressive plan is the bigger risk. The 16 lb cat above is a real run of the calculator, rounded to the nearest 10 kcal. — Malik Khurram

Stop the diet and call your vet if…

See your vet before you start any cat diet, and call right away if your cat:

• Refuses food for a day. VCA says a cat that hasn’t eaten for more than 2 days needs a vet immediately, and Cornell says fatty liver disease seems much more common in obese cats.
• Is losing more than 2% of its body weight a week.
• Is vomiting, hiding or unusually tired.
• Develops yellow gums, ears or eyes, which can be a sign of liver disease.
• Is losing weight without trying, especially if it’s older. Our cat age calculator shows when your cat reaches its senior years.