Weight and Fertility : Can Body Weight Impact Fertility ?

Body weight is a touchy subject, and it can become even more complex when talking about the relationship between weight and infertility. In fact, your weight, whether too high or too low, can impact fertility. Being overweight can prevent ovulation or prevent fertility treatments from working. (1) 

Maintaining a healthy weight provides many benefits when trying to conceive, and while a healthy weight doesn’t guarantee conception, it can definitely improve your chances of conceiving naturally.

We know that being both underweight or overweight can impact a woman’s ability to conceive, but what is a healthy weight? Being a healthy weight means different things to different people, and there are a few ways to measure it.

Using a BMI (body mass index) calculator is a great way to determine where your weight range falls. BMI takes into account a person’s weight in relation to how tall they are. When it comes to trying to conceive, a BMI below 30 is best, but a BMI of 18.5-24.8 is considered ideal for a healthy weight. (2)

Keep in mind that while calculating your BMI is a great tool, it is not going to tell you everything you need to know. BMI is a simple measurement that doesn’t take into account factors like waist or hip measurements, how much muscle mass someone has, or the distribution of fat.

Why Weight Impacts Fertility in Women

Maintaining a healthy weight in order to boost the chances of conception is important for many different reasons.

For one, weight can influence the amount of estrogen in your body. Being underweight can reduce how much estrogen you have in your body, which can cause your menstrual cycles to stop. (3)

Being overweight can increase your risk of insulin resistance which can then turn into type 2 diabetes, and insulin resistance has been linked to polycystic ovarian syndrome (PCOS.) PCOS causes an imbalance in both progesterone and estrogen levels, which can lead to disrupted menstrual cycles and fertility issues.

Another way weight impacts fertility has to do with the fact that being underweight can affect ovulation. A woman may not even have a menstrual cycle is she is very underweight, so ovulation may not even occur each month. A woman with a BMI under 18.5 is at risk for issues with fertility due to the fact that ovulation can be disrupted due to hormone imbalance. (4)

Why Weight Impacts Fertility in Men

Being overweight isn’t only problematic for a woman’s chance of conception, but being overweight can also affect male fertility as well. In men, obesity can significantly lower fertility by lowering testosterone, which can decrease the ability of a woman to produce healthy sperm. Obesity can also increase estrogen in men, which can then cause an increase in abnormal sperm.

Overall, it has been found that obesity in men negatively affects male fertility due to changes in hormone levels as well as changes in sperm function. The good news is that studies have found that positive dietary and lifestyle changes were able to reverse the damaging effects obesity has on sperm function. (5)

Weight and Fertility Complications

Being overweight or underweight also has the potential to cause pregnancy complications once a woman is pregnant. Obesity has the ability to harm the environment in which the egg and the sperm develop and being overweight while pregnant also poses the risk of high blood pressure, pre-eclampsia, gestational diabetes, infection, early labour induction, cesarean birth as well as the increased risk of miscarriage. Babies who are born to mothers who are overweight are also at a higher risk of certain health issues like childhood obesity. (6)

If a woman is undergoing IVF, being overweight can also affect IVF success rate. Being overweight can affect egg quality, which can make IVF success difficult with a woman using her own eggs. (7)