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Nutrition Nuggets
Your cat's nutrition is important for a healthy & happy life. petMD experts help you to know what to feed your cat, how much food to feed, and the differences in cat foods, so your cat gets optimum nutrition.
Nutrition Nuggets is the newest offshoot of petMD's Cat Nutrition Center. Each week Dr. Coates will use her expertise and wisdom to blog about the intricacies of cat nutrition.

Does Spaying and Neutering Make Cats Fat?

August 17, 2012 / (3) comments

Although most of my clients are eager to have their cats spayed or neutered (and no wonder — have you ever tried to live with a tom cat or queen in heat?), an almost universal concern is that their cats will get fat after the surgery.

 Research is a little ambiguous on the question of whether or not a cat’s energy needs decline after sterilization. Some studies seem to support this assertion, while others do not. Practically, however, veterinarians take this effect into account when determining how many calories a day a cat should be eating. For example, the resting energy requirements (RER) for an adult cat that weighs 10 pounds would be around 218 kcal per day. But we apply certain multipliers to this number to determine what an individual’s maintenance energy requirement (MER) actually is.

The MER is what we’re actually interested in. This is the number of calories a cat needs on a daily basis, taking into consideration her activity level, reproductive status, any illnesses she might have, whether or not we’re trying to help her lose weight, etc.

The "multiplier" for a typical spayed or neutered cat is 1.2, while that for an intact individual is 1.4, which leads us to a MER of 261kcal/day for the former and 305 kcal/day for the latter.

But even if spayed and neutered cats need fewer calories per day than do intact cats, that doesn’t mean they are destined to get fat. I recently ran across the results of two studies that showed when female and male cats had free access to food, they both ate significantly more post-surgery than they did pre-surgery. I can’t come up with a good explanation for this. Nobody argues that a cat’s needs for calories increase after spaying and neutering, so why are the cats eating more? Something to do with the hormonal changes going on in their bodies, I suppose.

In the study involving female cats, spayed kittens ate significantly more four weeks after the surgery (well after they’ve healed); this effect peaked 10 weeks after the spay. By 18 weeks post-surgery, spayed and non-spayed females were eating similar amounts. The study on male cats showed a dramatic increase in food intake in some cats during the first week post-surgery, with some cats experiencing a 10 percent increase in body weight.

While there are some differences in these two studies, the take home message is essentially the same. Portion control post-spaying and neutering is VERY important to prevent cats from gaining weight. I regularly argue that meal feeding is a healthier alternative for cats throughout most of their lives in comparison to free choice feeding, but even if you disagree, consider restricting your cat’s portions for 4-5 months after it has been spayed or neutered to help prevent weight gain.

Of course, you don’t want to scrimp on nutrition during this important time (after all, most cats are spayed or neutered when they are still young and growing), so make sure the food that you are offering packs a lot of nutritional bang per bite and is made from natural, high-quality ingredients.


Dr. Jennifer Coates

Image: Nailia Schwarz / via Shutterstock

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Comments  3

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  • Eating More After Surgery
    08/17/2012 05:57pm

    Have there been any studies about cats eating more after surgeries other than spay/neuter? Is it possible that it's simply part of the body's way of healing?

  • 08/20/2012 11:51am

    Not that I've seen. The fact that the cats' increased appetite continued for many weeks after the surgery is indicative that the healing process is not the only factor involved. I would consider a cat completely healed well before their appetites returned to normal in these studies.

  • 'Spay fat'
    08/20/2012 01:14pm

    Regardless of diet and portion control queens DO (or should say) CAN get fat, irreversibly, uncontrollably and permanently.

    I have a 12 yr. old queen who was spayed during... her first heat. She's been a tank (from a sleek, slender profile) ever since. I feed only premium foods. I returned to the vet shortly after who performed her surgery who was unconcerned and matter of factly stated that 'spay fat is normal'.

    I refuse to accept that notion. There's something that occurs physiologically, whether it's due to mid-heat surgery or otherwise I don't know. . which 'flips a switch internally that just makes them expand. I've seen other spayed queens who aren't huge or in any respect overweight, which was my expectation.

    I am Very concerned about this especially now that she is well into senior age as the extra weight cannot be good for her musculoskeletal structure and internal organs.




Photo of Jennifer

... graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999. In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado. She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms, Vet-Speak Deciphered for the Non-Veterinarian .

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics. Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.