Fertility and Weight

Human fertility is the ability to reproduce or generate life. It is a truly remarkable and complex process with the most amazing result, a child. If you are considering or planning a pregnancy, it is only natural to have many questions about what affects what when it comes to fertility. This particular article focuses on the importance of weight when it comes to obesity, and why looking after yourself and maintaining a healthy weight is so important to conception and pregnancy.

Why and how does weight affect fertility in women?

It has now been established that being over or underweight can lower your fertility, and hence your chances of getting pregnant. Female fertility depends on a monthly cycle which is under the control of certain chemicals called hormones. These hormones are produced by your body and are a kind of natural calendar, which when disrupted, can affect fertility.


Basically the important role of fat cells in women is that they convert testosterone, a male hormone which all women have some of, into the female counterpart oestrogen, which is a really important hormone in terms of regulating the monthly cycle. The more overweight you are, the more fat cells you have, and so the more abnormal the amount of oestrogen in your blood which diminishes your fertility.

The flipside to this is that while being overweight can reduce your fertility, being underweight isn’t particularly healthy either. Fat is needed for a healthy menstrual cycle, and in its absence you may not ovulate at all. This is on top of other health risks that are involved with being underweight.

Why and how does weight affect fertility in men?

While it has been known for a long time that weight affects female fertility, it’s only relatively recently that attention has been aimed at the fact that weight can also impact male fertility. If you are a man and overweight, than chances are that your sperm will suffer in terms of both sperm count and their motility, both important factors in being able to conceive. The reason behind this is that extra layers of fat can insulate your testicles, which produce sperm and need a cooler temperature to do their job properly.

Just like women, men who are underweight can also face serious infertility. Effective sperm production needs the nutrients and protein that are a part of maintaining a healthy weight, and in the absence of these important building blocks sperm quality is compromised. Even over-exercise can be bad for your fertility as raising your body temperature too much and too often will lower your sperm count.

What is a healthy weight?

We’ve talked a lot about why keeping a healthy weight is so important, but what is the ideal weight for fertility? When we talk about weight in this sense, we are actually referring to a measure called the Body Mass Index, which takes into account both your weight and height to give you a value that represents where you are in terms of the ideal weight. A BMI of 19-24 is perfectly healthy, and the ideal weight for your health and fertility, while a BMI above 25 will be detrimental to both as you will be overweight. A BMI below 19 would make you underweight, which again, can be very unhealthy.

What do I do if I want to get pregnant and am overweight?

If you are concerned about what effect your weight will have on your pregnancy, then it would definitely be wise to talk to your GP and see what advice you can get from that quarter. Generally speaking, if you want to improve your fertility, you will need to shed the extra fat, which is best done by adjusting your diet, drinking lots of water, and exercising regularly. If you are underweight than your diet might need a chance as well, but if you suffer from an eating disorder then consulting your doctor is the first step towards getting your weight back on track.

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