Does neutering cause weight gain in dogs?

The decision to have your dog spayed or castrated is an entirely personal one. But if you do choose to have you dog undergo this surgery it’s important to be aware that following it, you’ll need to make changes to their diet.

This is because spayed and castrated dogs are at an increased risk of being overweight or obese compared to intact dogs. And as with humans, dogs who are overweight or obese are at an increased risk of developing a number of health problems including cancer and joint problems.

Speculation put to rest

There has long been speculation that spaying or castrating a dog increases their risk of becoming overweight or obese following the procedure.

In 2013, this speculation was laid to rest when researchers showed that this surgery does indeed put spayed/castrated dogs at an increased risk of gaining weight.

At the same time, the paper disproved the idea that age was a factor in this risk. It showed that spaying/castrating at six months or younger didn’t increase a dog’s risk of gaining weight any more than if they underwent the procedure at an older age.

How neutering can increase weight gain

While this study confirmed that dogs are at an increased risk of becoming overweight or obese following spaying/castrating surgery, it didn’t conclusively explain the reasons why.

Nevertheless, there are a number of leading theories which could explain the link. Here’s two of the leading theories:

Decreased demand for energy

The first of these theories is pretty straight forward. Dog’s that have been spayed/castrated tend to have lower energy requirements than intact dogs. This – unsurprisingly – means that these dogs don’t need to consume as many calories as dogs who haven’t had this surgery. In short, spayed/castrated dogs don’t need to eat as much food.

On top of this, these dogs have a decreased metabolism compared to intact dogs. This means that the calories they do consume are converted to energy more slowly, again meaning they need to take in fewer of them.

Changes to hormones

When female dogs are spayed their ovaries and uterus are removed. As the source of the female sex hormones oestrogen and progesterone, removing these organs drastically reduces the levels of these hormones.

And when male dogs are castrated their testes – the source of the male sex hormone testosterone – are removed, meaning the levels of this hormone are dramatically reduced.
This reduction in sex hormones can have a variety of implications on a dog’s physiology.

For example, in female dogs the decrease in oestrogen levels makes weight gain more likely because it takes the brain longer to realise that the stomach is full, resulting in an increase in appetite.

Decreased levels of these sex hormones can also result in a lower metabolic rate, which as described above can lead to weight gain if calorie intake isn’t controlled. It can also lead to dogs becoming more lethargic and having a reduced urge to roam around or be physically active, which means they will burn fewer calories and be more prone to weight gain.

How to prevent weight gain in spayed and castrated dogs

While this 2013 study showed that spaying/castrating can increase your dog’s chances of becoming overweight or obese, perhaps more importantly it showed that this weight gain isn’t unavoidable.

It showed that with careful dietary management – particularly in the first two years after surgery – owners can reduce excessive weight gain in spayed/castrated dogs.

This means that following this surgery, owners need to be extra conscious of the foods they feed their dogs. Foods that are high in fat and low in nutritional content should be avoided, as should feeding table scraps.

It’s also important for owners to make sure they control portion sizes so that spayed/castrated dogs don’t eat too much. One way this can be done is to feed dogs smaller portions at regular intervals throughout the day. This means feeding your dog more regularly than two times a day, but not giving them extra food. Doing this can help your dog feel constantly full but they won’t be consuming extra food or calories.

It’s also vital that owners of dogs who are spayed/castrated make sure their pets get enough exercise. Some dogs may not have much desire to go for walks or to play, but nonetheless they need to, as it will help to keep their weight down.

The decision is yours

As with any surgical procedure, there are pros and cons to having your dogs spayed or castrated. It’s up to you as an individual which choice you make.

But when weighing up these pros and cons, remember that while the surgery puts your dog at an increased risk of gaining weight this can easily be prevented and controlled by reducing the number of calories your dog takes in and provide sufficient opportunities to exercise.

And for those who have already made the decision to have their dog spayed or castrated, it’s not too late to start making changes to your dog’s diet to help reduce their chances of gaining weight, and increase their chances of leading a healthy life.

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