Am I likely to be less fertile if I am obese?

Obese man

People who are classed as being overweight or obese are generally regarded as being unhealthy. Obesity poses several risks to our health, including heart disease, high blood pressure and diabetes but a problem that often gets overlooked is the fact that it can have a severe impact on your fertility. For females, for very unit their BMI is over 29, it reduces their chances of becoming pregnant in the next 12 months by a staggering 4%.

Here at First Fertility, we always encourage couples who are having problems conceiving to maintain a healthy weight. Regardless of any other factors, the closer you both are to a healthy BMI, the greater the chances you have of becoming pregnant in the next 12 months.

What is the ideal BMI for conception?

It is almost impossible to give an ideal weight due to height variances but, but your Body Mass Index (BMI) is a more accurate indication. A healthy BMI for an adult is between 18.5 and 24.9 while anything over 30 is regarded as being obese. There are several different tools available on the internet to help you calculate your BMI if you are unsure.

How does obesity impact fertility in women?

Maintaining an unhealthy body weight will almost inevitably have an impact on a woman’s chances of becoming pregnant. The most common fertility problems associated with being overweight in women are:

  • Menstrual disorders such as irregular periods
  • Problems with ovulation including failure to release eggs
  • Hormonal imbalances causing an array of fertility issues
  • Increased chance of developing polycystic ovary syndrome (PCOS)

At our clinic, we also make couples aware before treatment commences that being obese can also reduce your chances of success with fertility treatments such as in-vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI).

How does obesity affect male fertility?

Obesity can also have a significant impact on male fertility. Some of the most common fertility problems overweight males encounter include:

  • Erection problems (Erectile dysfunction)
  • Low testosterone
  • Lower sperm counts
  • Poor sperm motility and morphology

Returning to a healthy BMI will result in massive improvements in sperm quality and overall sperm count, although it may take in the region of three months before these changes are in evidence. This is the length of time it takes for sperm to develop.

Things to consider when preparing for pregnancy

If you and your partner are planning to try for a baby and one or both of you are overweight, it would be a good idea to start making some improvements to your lifestyle. Of course, you should seek the advice of a medical professional before you partake in any new or rigorous exercise program. However, you should consider taking moderate daily exercise, for example, walking 10,000 steps per day as well as making alterations to your diet. It is something that is even more important if you are about to undertake an assisted fertility program.

Couples should be aware that obesity not only decreases your chances of becoming pregnant, but it also increases your chances of a miscarriage or stillbirth. Exercise and dietary changes will help significantly, and you should also consult with your doctor about taking supplements such as folic acid.

Being overweight during pregnancy

As we have already touched upon, even if you do become pregnant, your chances of having a healthy baby are reduced if your BMI is high. In addition, the expectant mother also has a higher chance of developing pregnancy complications such as gestational diabetes, pre-eclampsia, high blood pressure and the need for a caesarean birth.

Babies who are born to overweight mothers may also experience health issues of their own, including childhood obesity and other more long-term issues. Even reducing your BMI by a couple of points can significantly increase your chances of becoming pregnant as well as mother and baby being healthy in the future.

How to achieve a healthy weight for pregnancy

If you and your partner have been trying to conceive without much success for a few months, it may be time to look at what lifestyle changes you could make to bring your weight down. Here are some relatively straightforward alterations that you could consider making:

Ensure that you eat a balanced diet comprising of lean meats, fish, poultry, fruit and vegetable, seeds and nuts as well as eggs. All of these foods are classed as being “fertility-friendly”

  • Cut back on processed and fried foods along with red meat, confectionery and pastries
  • Avoid artificially sweetened drinks and alcohol
  • Reduce food portion sizes and fill at least half of your plate with vegetable for lunchtime and evening meals
  • Make sure you eat breakfast
  • Do some moderate exercise each day
  • Reduce the amount of time that you spend sitting – this is particularly relevant to men who should try to reduce the temperature of the testes where possible
  • Set realistic weight and BMI goals. Aiming for drops that are too large may be de-motivating while too little may not achieve the desired objective

Even if you don’t see significant changes in your weight, making these alterations will make a difference to your overall health which, in itself, can increase your chances of becoming pregnant.

How does being underweight affect fertility?

While our focus is on how obesity impacts on fertility, it is worth noting that being underweight, having a BMI of below 18.5, can also reduce a woman’s chances of becoming pregnant. If the female is underweight, it can cause hormone imbalances as well as potentially causing problems with ovulation. If you are concerned about being underweight, we would recommend that you speak to a dietician.


Maintaining a healthy body weight is vital if you are experiencing problems conceiving. If you have been unsuccessfully trying for a baby for 12 months or more, here at First Fertility, we can help. However, as we have discussed, achieving a healthy BMI will play an essential role in the success of your treatment.