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Cats Gain Weight after Spaying

About 80% of American household cats are spayed or neutered, which is invaluable for the many health and social benefits. However, most studies have found that cats gain weight after spaying. But it’s possible you didn’t notice many changes if your cat was spayed when she was a kitten, since she was still growing. Though, if you had your cat spayed as an adult, you might have discovered that she’s heavier than she once was.

Even if you have a cat that put on some extra pounds post-spay, nevertheless, with your help, they aren’t destined to become obese. Continue reading for ways to combat the weight gain, and to keep obesity at bay.

tortoiseshell shorthair cat trying to drink out of fountain outside
Meow Meow is too heavy to lift herself up enough to drink out of the fountain!

Why Cats Gain Weight After being Spayed

cat eating big bowl of cat food out of blue bowl outside
Photo by itsmeseher on

I never experienced a cat in heat before Itty. But just to recap feline estrous: female cats are in heat every few days for at least 10 solid months of the year! Plus, their hormones are raging, which includes estrogen being released, on and off, during this 10 month long period.

Thus, when Itty was in heat, she had no time for food. Because she was distracted. And it wasn’t until she was out of heat that she would finally eat food. However, a few days later she would be back into her heat cycle. Until she was spayed. Since she no longer has all those hormones driving her other needs, I have theories about what caused her starvation after surgery, then over-eating, and therefore, weight gain.

Regardless of my theories, multiple studies have revealed that cats gain weight after being spayed because:

  • they lose estrogen, which decreases metabolic rate
  • metabolic rate is decreased, thus their energy needs are decreased
  • plus, spayed cats need about 20-25% less food than intact cats for ideal weight
  • in addition, appetites can increase because estrogen has been shown to decrease appetite
  • and finally, some spayed cats are under-exercised and over-fed.

Age Cat is Spayed is a Factor in Weight Gain Post-Spay

person in scrubs performs surgery on sedated cat
Photo by Pranidchakan Boonrom on

This might actually surprise you, but adult cats are more at-risk for gaining weight, resulting in obesity, post-spay than kittens. Although, depending on which site you look at, you might get a totally different answer. But I was suspicious of this myself, after witnessing the effects of hormones during Itty’s estrous cycles. And considering that spaying a cat is similar to a human hysterectomy, it has to be such a shock to their systems.

In any case, this study published in 2017, involved only kittens (15-52 weeks). And the purpose was to determine their total energy needs by inspecting the significance of spaying, age when spayed on intake, and body weight. Given the study only included kittens, half were spayed/neutered early compared to the rest, which was conventional. Or they were spayed/neutered at a later date, when they hit puberty.

The results revealed that the kittens spayed/neutered early, before reaching sexual maturity and their first heat cycle, gradually gained weight through normal growth. Whereas the kittens spayed/neutered after sexual maturity showed sudden increases in feeding, hence gaining weight more quickly, and becoming overweight. 

A Word About Hyperphagia and Leptin Resistance

Digital image of calico cat eating a big steak dinner
Digital Art, Courtesy of Sarah Smith

Hyper-what? Well, up till now I’ve just been referring to Itty’s need for food post-spay starvation. Though, it turns out there’s an actual word for the condition. Also, it appears that other pet parents are unaware of this term as well. Because when I looked up this issue about starving cat post surgery, there were tons of others with the same problem. They just didn’t have a word for it either. However, it is most commonly associated with injury to the hypothalamus.

But there’s also leptin, which is a hormone that helps our bodies maintain normal weight on a long-term basis. While normally leptin increases when food is eaten, signaling the hypothalamus to tell the brain that we and our pets are satisfied, mammals with too much or too little leptin don’t get those signals. Additionally, those with higher levels of leptin, who eat more and gain more weight, indicate leptin resistance. Therefore, from what I’ve read, there’s obviously a connection between spaying/neutering and leptin resistance. For instance, this 2002 article from The Journal of Endocrinology and Metabolism says:

One means through which estrogen may affect energy balance is through influencing synthesis of the hormone leptin. Leptin is a hormone produced by adipocytes (10) that is thought to affect energy intake and expenditure (1113). 

Leptin in Postmenopausal Women: Influence of Hormone Therapy, Insulin, and Fat Distribution* 
B. A. Gower,  T. R. Nagy,  M. I. Goran,  A. Smith,  E. Kent

Scientists used to think it was just cats eating too much. Or that their owners were too lazy to play with them. However, with more research done on leptin and its function, it makes more sense that something else is going on. For example, all the starving cats post-spay. It’s the classic chicken or egg question: which came first, the eating disorder or the starving cat? Since I’ve experienced this firsthand, and I know how small Itty was prior to spaying, I can tell you how off the charts hungry she has been. She has no idea that she’s full. Thus, once cats hit puberty and are then spayed, hormonally something happens. Or doesn’t happen like it’s supposed to. And so cats eat. And eat, because they don’t know they’re full.

What You can do to Prevent Obesity Post-Spay

If your cat was spayed recently, or is going to be, just know that she is going to gain some weight. It’s a given, at least with everything I’ve read. Despite that, to prevent obesity

2 cats eating out of huge bowls outside by red door
Photo by Arzum Kaya on

Instead figure out your cat’s daily caloric needs using this site. And then adjust their food intake by giving your cat several smaller, measured meals throughout the day.

  • Also, avoid feeding your fur baby table scraps or treats
white cat eating from crystal bowl on fully furnished table
Photo by cottonbro studio on

Most of the time cats seem finicky. Until they get spayed. Next, they appear starving. And then any type of food is fair game to them then. Be strong, my friend. Be strong.

  • And promote physical activity.
2 different cats playing on big multi-level cat scratching post
Photo by Arina Krasnikova on

Get some toys and play with your cat. Or even explore your backyard together. But do something that distracts them from wanting to eat all the time.

Before Itty went into her very first heat cycle, she and I would play together all the time. However, once she hit puberty, she was no longer herself due to those crazy hormones. While Itty is now spayed and no longer distracted, she’s up to playing and exploring again.

  • Lastly, make an appointment with the vet.
2 different people holding and examining a white cat
Photo by Gustavo Fring on

If after all of these steps and you’re still fighting the daily hyperphagia, or starvation, then it’s time to see the vet. You can’t do this on your own; you need some help.

In fact, I’m planning on making an appointment for Itty as well. Because I’ve already changed her diet. Though, I’m not sure how much fat content I’m supposed to cut out of her diet, since fat is vital to their diet. And I suspect she has leptin resistance. The good news on that is there is treatment to reverse leptin resistance. But the vet probably needs blood work before starting any treatment.

In Conclusion

Most cats gain weight after being spayed due to the loss of estrogen. And the hormone leptin experiences resistance after spay as well, which leads cats to eating more, and thus, gaining more weight. However, there’s things we can do to help our cats from becoming obese: providing smaller meals, encouraging exercise, and talking with the veterinarian.

If you’ve already had your cat spayed for some time, did your cat experience hyperphagia? Also, did she gain weight? And how did you handle the changes?

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I breed pure Black Ameraucana chickens and Easter Eggers that are Black Ameraucana mixed with either Cuckoo Maran or Barred Rock. And I donate eggs to people or organizations in need.

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