A Woman’s Weight and Fertility

Pregnant woman weighing herself on a bathroom scale

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There are different opinions on the matter of weight and fertility, but medical professionals (especially gynaecologists and reproductive endocrinologists) will tell you that weight DOES matter when it comes to fertility. Both underweight and overweight women tend to have a more challenging time conceiving. You might be surprised to know that the same is true for men.


Why, you might ask, would weight affect one’s fertility? A woman’s body fat is directly correlated to the hormones her body produces. To put it simply, too little fat can result in the insufficient production of key reproductive hormones, while too much fat can cause overproduction of these said hormones.


Recommended Body Mass Index (BMI)

The recommended ‘healthy’ BMI range for women who are trying to conceive is between 18.5 and 24.9. A BMI that is under 18.5 is considered ‘underweight’, over 25 is ‘overweight’, and anything beyond 30, ‘obese’.


To check for your BMI, you may click on this link: http://www.bmi-calculator.net/


Being Overweight

Women who are overweight (with a BMI of 25 or more) usually have a potential imbalance of the hormone estrogen. Fat cells produce estrogen, thus, women with more fat cells tend to have higher levels of this hormone. Excess estrogen can impact fertility negatively – it essentially acts as a birth control of sorts by preventing adequate ovulation from occurring.


Polycystic Ovary Syndrome (PCOS) is another common cause of infertility. This condition is closely linked to weight gain as well as difficulty in losing weight.


Being Underweight

Women who are underweight (with a BMI of less than 18.5), on the other hand, might also have an insufficient production of key hormones. This may also lead to ovulation issues – making it difficult to achieve pregnancy. Insufficient production of gonadotrophin-releasing hormone (GnRH) can lead to inadequate development of a uterine lining that supports pregnancy. GnRH is also responsible for triggering the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) – these hormones are necessary in the development of eggs and for ovulation to occur.


Male Infertility

Not everyone is aware of this but yes, male infertility can also be affected by weight. How? Low sperm count and sperm motility problems might occur more in overweight men because of the excess layers of fat surrounding the testicles. Too much heat around the testicles leads to an increase in temperature. As a result, this increase can negatively affect the development of sperm, or worse, kill it.


For men, the same BMI ranges apply. The recommended BMI range is 18.5 to 24.9 when trying to conceive.


Bottom Line

It is best that men and women know how being underweight or overweight can greatly impact their ability to get pregnant. The good news is, if you will work on bringing your body weight within the ‘healthy’ BMI range, it often leads to your body’s normal hormonal balance restoration.


For more questions on fertility, it is best to consult Dr. Fay Weisberg.

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