Does neutering make dogs and cats gain weight and become obese?

Answer:

  • The loss of estrogens and androgens (sex hormones) from neutering dogs and cats causes a decrease in metabolic rate, thus their energy needs are lower.1
  • Neutering a pet is linked to an increased risk of unhealthy weight gain and obesity if there is no change in diet or feeding plan at the time of surgery. Pets should have a reduction in caloric intake post surgery.
  • It is a nutritional milestone at the time a pet is spayed or neutered. They must have some change in the amount or type of food to assure they stay at a healthy weight and body condition. If neutered pets are fed the same as intact pets, they will gain weight.2-6
  • Androgens and estrogens stimulate roaming behavior and general physical activity so intact pets are more active.7,8
  • Most neutered pets are overfed and underexercised and are twice as likely to become obese.
  • In general, neutered cats require only 75-80% of the food needed by intact cats to maintain optimal body weight.9
  • Appetites may increase following surgery. Estrogen has been shown to decrease appetite.

More supporting facts:

  • 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.10
  • Body weight and BCS should be obtained every two weeks for four to five months after neutering to confirm maintenance of normal body weight and body condition.10
The Science Behind our Recommendations
  1. 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.
  2. 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.
  3. 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.
  4. Harper EJ, Stack DM, Watson TD, Moxham G. Effects of feeding regimens on bodyweight, composition and condition score in cats following ovariohysterectomy. J Small Anim Pract. 2001 Sep; 42(9):433-8.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.