Does weight influence your egg quality?

In 2020 Rebel Wilson amazed the world with her ‘year of health’, losing four stone

She shared on Instagram that her weight loss has also been focused on boosting her health for “fertility” reasons.  She shared with her 9.3 million followers on Instagram: “I was thinking about fertility and having good quality eggs in the bank, so I was like, ‘OK, I’m going to do this. I’m going to get healthy.” 

Inspired by Rebel’s actions, at a time when many of us are making New Year’s resolutions, we asked Professor Tim Child, Medical Director, Oxford Fertility and the Fertility Partnership, to what extent weight influences our fertility and if it changes egg quality:  

Weight has a significant role to play in fertility, particularly for women.  If you’re a woman who is underweight or overweight, it can impact the chances of you conceiving.   

Body Mass Index (BMI) is a measure of your body fat based on height and weight.  A BMI of below 18.5 is considered underweight, above 25 overweight, and 30 or more obese.  To find out your BMI, divide your weight in kilograms (kg) by your height in metres (m), then divide the answer by your height again to get your BMI, or use one of the many online BMI calculators.

In both underweight and overweight women, changes start to take place in the body that can reduce the chance of conception 

Weight doesn’t alter the quality of your eggs. Instead your periods may become irregular which can be a sign that you’re not ovulating (releasing an egg) every month. Even if the periods are regular, the chance of an embryo implanting in the womb can be reduced, and the risk of miscarriage higher for women who are very overweight (BMI >30). It’s not clear why this is the case but losing weight can reverse the problem, leading to normal embryo implantation rates.

When weight is causing fertility problems then, once a woman reaches a healthy weight, the majority of couples achieve a natural conception

For those where weight isn’t the primary cause, and IVF is needed, achieving a BMI of between 19 and 30, will help. Women within this weight range achieve a higher success rate than others.  In fact NHS guidelines from the National Institute for Health and Clinical Excellence (NICE) recommend this range for effective IVF treatment and all  Clinical Commissioning Groups set this as a criteria for NHS funded IVF treatment.   

 It’s also important to achieve a healthy weight for when you do conceive, to maximise the chance of a healthy pregnancy for you and your unborn child.  Having a BMI outside of the normal range can increase the risk of pregnancy complications such as pregnancy loss, diabetes and high blood pressure.

We recognise it’s not always easy to lose weight

Some people also suffer from health conditions such as Polycystic Ovarian Syndrome (PCOS) that affects hormone levels and can make losing weight harder.   So if you have been trying to lose weight and need extra help, see your GP or Dietician. 

 We shouldn’t completely ignore a man’s weight  

There is a link between a man’s weight and sperm quality, but as yet it’s not known how this impacts fertility.  But this shouldn’t put you off aiming for a healthy weight, supporting your partner in their goals and preparing for the active life of being a dad.       

 So Rebel Wilson’s weight loss will make a big impact on her fertility and health overall

If you are outside of the healthy BMI range it is a great idea to make plans to manage your weight.  But we know its easier said than done and if you need help, there are services provided by your GP that can assist  https://www.nhs.uk/live-well/healthy-weight/how-your-gp-can-help-you-lose-weight/ 

Huge thanks to Professor Tim Child, Medical Director, Oxford Fertility and the Fertility Partnership