Why Spayed/Neutered Pets Are More Prone to Weight Gain (and What You Can Do About It)

Spaying and neutering are crucial for controlling pet overpopulation and improving your pet’s health. However, one common concern among pet owners is the potential for weight gain after these procedures.

Author: Emi Kooyman | Founder

Why Spayed/Neutered Pets Are More Prone to Weight Gain

1. Hormonal Changes Post-Surgery

Spaying (removal of ovaries and uterus) or neutering (removal of testes) reduces the production of sex hormones like estrogen and testosterone. These hormones play a role in regulating metabolism and appetite:

• Increased Appetite: After sterilization, pets may experience a surge in hunger due to reduced estrogen levels, which normally suppress appetite. Studies show that neutered female dogs eat more food than intact females when fed identical diets.

• Lower Metabolic Rate: Neutered pets have a reduced resting metabolic rate. For example, research shows that neutered cats have a 28-33% lower metabolic rate compared to intact cats. This means they burn fewer calories at rest, making it easier to gain weight if their food intake isn’t adjusted.

2. Reduced Physical Activity

Male pets, especially dogs, may become less active post-neutering because they no longer exhibit roaming or mating behaviors driven by testosterone. While this is a behavioral benefit of sterilization, it also means fewer calories are burned through daily activity.

3. Overfeeding and Mismanagement

• Many pet owners are unaware that spayed/neutered pets require fewer calories than intact animals. Without adjusting portion sizes or feeding habits post-surgery, pets can quickly gain weight.

• Ad libitum feeding aka “free-feeding” (leaving food out all day) is particularly problematic for sterilized pets, as they are more likely to overeat compared to intact animals.

The Risks of Obesity in Pets: Spayed/Neutered and Intact

Obesity is more than just extra weight—it’s a serious health issue that can shorten your pet’s lifespan and reduce their quality of life. While spayed/neutered pets are at a higher risk of obesity due to hormonal changes affecting metabolism and appetite, the risk is not exclusive to them. Intact pets can also become obese if their diet and activity levels are not properly managed. Factors such as overfeeding, lack of exercise, breed predisposition, and owner habits play significant roles in obesity for all pets, regardless of their sterilization status.

Common risks include:

1. Diabetes Mellitus: Obese pets are at greater risk of developing diabetes due to insulin resistance.

2. Joint Problems: Excess weight places stress on joints, increasing the likelihood of arthritis or mobility issues.

3. Heart Disease: Carrying extra weight can strain the cardiovascular system.

4. Reduced Lifespan: Studies show that maintaining an ideal body condition can extend a pet’s life by up to two years.

What You Can Do About It

The key to preventing weight gain in spayed/neutered pets lies in proactive management of diet and lifestyle. Here’s how:

1. Adjust Caloric Intake

• After surgery, reduce your pet’s caloric intake by 20-30%, as their energy needs decrease significantly.

• Use the Resting Energy Requirement (RER) formula as a starting point for calculating daily caloric needs. RER can be calculated by multiplying the animal’s body weight in kilograms raised to the ¾ power by 70, for example, a 10kg (22lb) adult neutered dog of healthy weight needs RER = 70(10kg)3/4 ≈ 400 Calories/day. The daily energy intake should be limited to prevent rapid weight gain in neutered dogs; 1.6 x RER is a good starting point. For some breeds and individual dogs, it may be necessary to lower the energy intake of neutered dogs to 1.2 to 1.4 x RER

2. Choose the Right Diet

• Opt for low-fat, low-energy-dense diets specifically formulated for weight management in sterilized pets. These diets help control calorie intake without leaving your pet feeling hungry.

• Avoid high-fat treats or table scraps, which can quickly add unnecessary calories.

3. Practice Portion Control

• Measure food portions accurately using a kitchen scale or measuring cup rather than estimating by eye.

• Divide daily meals into smaller portions fed multiple times a day to prevent overeating.

4. Encourage Regular Exercise

• Aim for at least 30 minutes of physical activity daily for dogs (e.g., walks, fetch games) and interactive play sessions for cats.

• Introduce stimulating toys like puzzle feeders or laser pointers to keep your pet active indoors.

5. Monitor Body Condition

• Use a Body Condition Score (BCS) chart to assess whether your pet is at an ideal weight. A BCS of 4–5 out of 9 is considered healthy.

• Regularly weigh your pet at home or during veterinary visits to track progress.

6. Consult Your Veterinarian

• Work with your vet to develop a customized diet and exercise plan tailored to your pet’s needs.

• Schedule regular wellness exams to monitor your pet’s weight and overall health.

Debunking Myths About Spaying/Neutering and Obesity

It’s important to address common misconceptions about spaying/neutering:

• Myth: Spaying/neutering causes obesity.

• Fact: Obesity is caused by overfeeding and lack of exercise—not sterilization itself.

By educating pet owners about these nuances, you can empower them to make informed decisions about their pets’ care.

Conclusion

While spayed/neutered pets are more prone to weight gain due to hormonal changes, obesity is entirely preventable with proper care. By adjusting diet, encouraging exercise, and monitoring body condition, you can ensure your pet remains healthy and happy post-surgery.

At Spay Neuter Vets, not only do we provide spaying and neutering, but also we take on the opportunity to educate pet owners about the benefits as well as the risks, to enhance the well-being of individual pets and strengthen trust with our clients, in their pets’ long-term health journey.

As we learn that spaying/neutering your pets does not directly cause weight gain, don't wait and hesitate any longer. We will help to ensure you have sufficient information to navigate taking care of your pets after their surgery. Check out our Spay/Neuter Packages or book your appointment today!