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What nutritional changes need to be made after neutering a pet to prevent obesity?


  • It is a “nutritional milestone” at the time a pet is spayed or neutered. The amount and/or type of food must be changed to assure the pet stays at a healthy weight and body condition. If neutered pets are fed the same as intact pets, they will gain weight.1-5
  • After neutering, a nutritional evaluation should be performed to make sure the pet’s nutritional requirements are met. Young adult dogs and cats may even require low-calorie foods.6
  • Body weight and body condition score (BCS) should be obtained every two weeks for 4-5 months after neutering to confirm maintenance of normal body weight and body condition.6
  • In general, neutered cats require only 75-80% of the food needed by intact cats to maintain optimal body weight.7

More supporting facts:

  • Neutering dogs and cats causes a decrease in estrogens and androgens (sex hormones), resulting in a lower metabolic rate. Therefore, the pet’s energy needs are lower.
  • Since estrogen has been shown to decrease appetite, appetites may increase after surgery.
  • Increased levels of androgens and estrogens in intact pets stimulate roaming behavior and general physical activity so these pets are more active.8,9 Therefore, without a change in diet, neutered pets may become overfed and under-exercised and at a greater risk of becoming obese.
The Science Behind our Recommendations
  1. 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 Jun;133(6):1866-74.
  2. Martin L, Siliart B, Dumon H, Backus R, Biourge V, Nguyen P. Leptin, body fat content and energy expenditure in intact and gonadectomized adult cats: a preliminary study. J Anim Physiol Anim Nutr (Berl). 2001 Aug; 85(7-8):195-9.
  3. Harper EJ, Stack DM, Watson TD, Moxham G. Effects of feeding regimens on body weight, composition and condition score in cats following ovariohysterectomy. J Small Anim Pract. 2001 Sep; 42(9):433-8.
  4. Jeusette I, Daminet S, Nguyen P, Shibata H, Saito M, Honjoh T, Istasse L, Diez M. Effect of ovariectomy and ad libitum feeding on body composition, thyroid status, ghrelin and leptin plasma concentrations in female dogs. J Anim Physiol Anim Nutr (Berl). 2006 Feb; 90(1-2):12-8.
  5. McGreevy PD, Thomson PC, Pride C, Fawcett A, Grassi T, Jones B. Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved. Vet Rec. 2005 May 28; 156(22):695-702.
  6. Toll PW, Yamka RM, Schoenherr WD, Hand MS. Obesity. In: Hand MS, Thatcher CD, Remillard RL, Roudebush P, Novotny BJ, eds. Small Animal Clinical Nutrition 5th ed. Topeka, KS: Mark Morris Institute; 2010: 512.
  7. Root MV, Johnston SD, Olson PN. Effect of prepuberal and postpuberal gonadectomy on heat production measured by indirect calorimetry in male and female domestic cats. Am J Vet Res. 1996 Mar; 57(3):371-4.
  8. Hart BL, Barrett RE. Effects of castration on fighting, roaming, and urine spraying in adult male cats. J Am Vet Med Assoc. 1973 Aug 1; 163(3):290-2.
  9. Hopkins SG, Schubert TA, Hart BL. Castration of adult male dogs: effects on roaming, aggression, urine marking, and mounting. J Am Vet Med Assoc. 1976 Jun 15;168(12):1108-10.