Do Spay & Neutered Pets Need Different Nutrition?
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Do Spay and Neutered Pets Need
Different Nutrition?

Donna M. Raditic, DVM, DACVIM (Nutrition)

Board Certified Veterinary Nutritionist, Athens, GA

Do Spay and Neutered Pets Need Different Nutrition?


Studies tell us that 52% of dogs are overweight by 1.5-2 years of age, and 21% of cats are already overweight by 6 months.1,2,3,4

In private practice, I recall ensuring our puppies and kittens were growing, but staying lean with an optimal body condition score (BCS) of 5/9. Yet many would return for their first annual visit already overweight, with a BCS of 6-7/9. What was I missing? Why were these dogs and cats becoming overweight so quickly?

I often say hindsight is 20/20, and I certainly feel that way looking back at my nutritional recommendations when I was a general practitioner. While there are many human factors associated with weight gain (overfeeding, over treating, under exercising), we often underappreciate the impact spay and neuter surgeries have on our patients.


Today nearly 90% of U.S. pets are spayed or neutered.

Spay and neuter (S/N) are well-known risk factors for the development of obesity.2,5,6 Yet we have struggled to comprehend the profound impact S/N surgery has on our patients’ caloric and nutrient requirements. We certainly know S/N are beneficial for our patients. However our spayed and neutered dogs are at twice the risk of becoming obese, while the risk in cats is tripled.7,8


Removal of sex hormones decreases metabolic rate.

A S/N dog requires 30% less calories, and a S/N cat requires 24% less calories.5,6 It’s important to keep in mind that sex hormones, especially estrogen, also have a modulating effect on appetite.6 Without sex hormones the S/N dog can have a 60% increase in appetite, while the appetite in the S/N cat can increase 23%.9,10,11 This increase in appetite can occur just three days post S/N.12 These physiological changes are not just profound, they’re also permanent in our S/N patients. The simultaneous decline in metabolism and increase in appetite leave our patients with very unique (and challenging) nutritional needs.

What do these percentages mean for your S/N patients? Let’s apply them to a case example: Sammy is an 18-month-old male Golden Retriever with body weight 35 kg and ideal body condition of 5/9, consuming 1612 calories from an over-the-counter dry commercial puppy diet. Sammy is recently neutered, so let’s now apply the research:

  1. Sammy’s metabolic rate decreases, and he now needs 30% less calories, so the recommendation should be to feed him 1128 calories per day.
  2. Post neuter, Sammy has an appetite increase of 60%; if fed ad lib he could consume 2579 calories.

This is around a 1450-calorie per day difference between what Sammy should be eating and what his increased appetite could have him consuming post neuter! To help you visualize this, a puppy food typically contains around 380 calories in a dry measuring cup, so here we could be talking about Sammy feeling he needed more than double the amount of calories his metabolic rate requires.

When you do the math and think about the physiological changes that occur in our S/N pets, it is easy to understand why at that first annual visit we have many young patients already overweight. And in my clinical experience as a veterinary nutritionist, I view an overweight young cat or dog with a BCS of 6-7/9 already on the pathway to obesity. As veterinarians, we understand that spay and neuter alter more than anatomy. Recognizing the physiological changes and making specific nutritional recommendations to address them is part of our responsibility in providing best care for our S/N patients. 8-10

Spayed and neutered cats and dogs need specialized nutrition.

It is clear to me that we indeed need specialized nutrition for spayed and neutered cats and dogs. We need specific diets that address their unique needs. We need to address the permanent physiologic changes that occur after S/N:

  • An increased appetite
  • Need for less calories, without compromising nutrient intake

What type of formula would best meet the unique needs of S/N pets? Appropriate S/N diets should be moderate in caloric density, high in protein and high in fiber to address the specialized nutritional needs of S/N dogs and cats.13

  • Both protein (amino acids) and fiber help to reduce voluntary intake and begging behavior.14,15
  • Fiber can help with “satiety,” that sensation of feeling full. Certain amino acids may also help trigger satiety.14-16


What else should you look for in a S/N diet?

As our patients undergo S/N surgery at different ages, be sure to select a diet that has been formulated for the life stage that matches your patient’s needs. Remember, nutrient requirements (amino acids, fatty acids, vitamins and minerals) for puppies and kittens can be up to twice those of adult pets.16 The 2021 AAHA Nutrition & Weight Management Guidelines state that “because [spay and neuter] surgery usually occurs at a young age, it is challenging to feed to support sufficient growth while avoiding excess [calories]. Switching too early [to an adult formulation] may affect nutrients necessary to support development.”1 Switching a still-growing puppy or kitten to an adult diet prematurely may potentially result in underfeeding nutrients that are needed for optimal growth and development.16


Excess calories and calcium play a role in developmental disease in large breed puppies.

When selecting a diet for large breed puppies, always look for the AAFCO growth statement that includes growth of large-size dogs: “[Pet Food Name] is formulated to meet the nutritional levels established by the AAFCO Dog Food Nutrient Profiles for growth/all life stages including growth of large-size dogs (70 lbs. or more as an adult).”


When you fully understanding the impact S/N has on our patients, it is evident that these patients need specialized nutrition.

Using appropriate diets that are specialized for our S/N patients allows veterinarians to quickly provide clients with precise nutritional recommendations, while also addressing the patient’s increased risk for obesity. This, to me, is the proactive nutrition the 2021 AAHA guidelines are discussing.


1. Cline M, Burns K, Coe J, et al. 2021 AAHA Nutrition and Weight Management Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2021;57(4):153-178.

2. German AJ, Woods GRT, Holden SL, Brennan L, Burke C. Dangerous trends in pet obesity. Vet Rec. 2018;182(1):25.

3. Lund EM, Armstrong PJ, Kirk CA, Klausner JS. Prevalence and risk factors for obesity in adult cats from private US veterinary practices. Intern J Appl Res Vet Med. 2005;3(2):88-96.

4. Lund EM, Armstrong PJ, Kirk CA, Klausner JS. Prevalence and risk factors for obesity in adult dogs from private US veterinary practices. Int J Appl Res Vet Med. 2006;4(2):177-186.

5. Linder DE, Mueller M. Pet obesity management beyond nutrition. Vet Clin North Am Small Anim Pract. 2014;44(4):789-806.

6. Allaway D, Gilham M, Colyer A, Morris PJ. The impact of time of neutering on weight gain and energy intake in female kittens. J Nutr Sci. 2017;6:e19.

7. Nguyen P., Dumon HJ, Siliart BS, Martin LJ, Sergheraert R, Biourge V. Effects of dietary fat and energy on body weight and composition after gonadectomy in cats. Am J Vet Res. 2004;65(12):1708-1713.

8. Lefebvre SL, Yang M, Wang M, Elliott DA, Buff PR, Lund EM. Effect of age at gonadectomy on the probability of dogs becoming overweight. J Am Vet Med Assoc. 2013; 243(2):236–243.

9. Jeusette I, Detilleux J, Cuvelier C, Istasse L, Diez M. Ad libitum feeding following ovariectomy in female Beagle dogs: Effect on maintenance energy requirement and on blood metabolites. J Anim Physiol Anim Nutr (Berl). 2004;88(3-4):117-121.

10. Kanchuk ML, Backus RC, Calvert CC, Morris JG, Rogers QR. Weight gain in gonadectomized normal and lipoprotein lipase-deficient male domestic cats results from increased food intake and not decreased energy expenditure. J Nutr. 2003;133(6):1866-1874.

11. Kanchuk ML, Backus RC, Calvert CC, Morris JG, Rogers QR. Neutering induces changes in food intake, body weight, plasma insulin and leptin concentrations in normal and lipoprotein lipase-deficient male cats. J Nutr. 2002; 132(6 Suppl 2):1730S-1732S.

12. Wei A, Fascetti AJ, Kim K, et al. Early effects of neutering on energy expenditure in adult male cats. PLoS One. 2014;9(2):e89557.

13. Phungviwatnikul T, Valentine H, de Godoy MRC, Swanson KS. Effects of diet on body weight, body composition, metabolic status, and physical activity levels of adult female dogs after spay surgery. J Anim Sci. 2020;98(3):skaa057.

14. Jewell DE, Toll PW, Novotny BJ. Satiety reduces adiposity in dogs. Vet Ther. 2000;1(1):17-23.

15. Weber M, Bissot T, Servet E, Sergheraert R, Biourge V, German AJ. A high-protein, high-fiber diet designed for weight loss improves satiety in dogs. J Vet Intern Med. 2007;21(6):1203-1208.

16. Officials AAFCO. Model Regulations for Pet Food and Specialty: Pet Food Under the Model Bill. In: Green K, ed. 2019 Official Publication. Champaign, IL, 2019;139-225.