Is there an ideal weight to get pregnant? No. Can gaining or losing weight help you get pregnant? Probably.

You don’t need to maintain an ideal weight or a certain body type to get pregnant. However, having a normal BMI certainly gives you better chances of getting pregnant as compared to someone who is significantly overweight or underweight.

Excessive weight loss or obesity can also affect the success of fertility treatments as your body does not conceive if it is not conducive for maintaining a pregnancy.

What is BMI and how does it influence your fertility?

Body mass index (BMI) is a measure of your health based on your weight and height. You can calculate your BMI using the below:

UnderweightBMI under 18.5
Normal weightBMI 18.5 – 25
OverweightBMI 25 – 30
ObesityBMI over 30

Being in the normal weight range gives you the most chances of having a successful pregnancy but despite a normal BMI, your body may not be healthy enough to conceive.

This is because BMI does not take into account the body fat and muscle proportion, which influences your hormones and in turn affects your fertility.

When I was a normal-weight, normal-BMI girl, obsessed with losing body fat and gaining muscle, I started developing facial acne. I took the prescribed tests on doctor’s insistence and found that my hormones were thrown off balance. The Estrogen levels dropped and messed my period schedule.

I was lucky to be alarmed in time. I went back to an easier exercise routine and a more balanced diet (including carbs and fats!) and within three months the hormones went back to normal.

How does weight affect fertility in women?

Excess weight and fertility

Estrogen, the main female sex hormone, is primarily produced by your ovaries, but over 30 percent of estrogen in also produced by your body fat cells. So being the right fat percentage is far more important than being the right BMI.

But if you are in the healthy BMI range, you are likely to have normal fat content in your body, producing healthy amounts of estrogen.

However, with excessive much body fat, your cells may be producing too much estrogen, which can cause irregular menstrual cycles and disrupt your regular ovulation cycle.

Research finds that higher levels of estrogen can actually keep you from ovulating at all, which means there is no chance of conceiving.

Irregular menstrual cycles are common in obese women, and according to the large Dutch study cited above, the chances of conception decrease steeply as the woman’s BMI climbs over 29.

Female fertility drops with increase in BMI

While irregular periods are an indication of possible ovulation problems, even if you have regular periods you may have a hard time getting pregnant if you are obese.

Besides lowering your chances of conceiving naturally, obesity impairs the chances of success in IVF and also increases the risk of miscarriage and birth defects in babies, according to the ASRM.

Fertility in underweight women

As discussed above, it is not really the weight, but having optimal fat in your body that influences your hormones and your fertility. Runners who train for marathons and professional athletes, who have more muscle than fat, often have lower production of estrogen and mild periods.

Again, the ovulation is affected and they have trouble getting pregnant.

Besides, a healthy, nourished body is important to carry a pregnancy to term. So, if you don’t have sufficient padding of fat, your body will not be ready for pregnancy, which means conception will be difficult even with fertility treatments.

Excessive training can impair female fertility

So if you have light periods and hard training sessions, you may want to cut down on those fat-burning sessions and include more fats in your diet.

“We believe it is likely that physical activity at a very high or very low level has a negative effect on fertility, while moderate activity is beneficial,” said Sigridur Lara Gudmundsdottir, a researcher in this Norwegian University of Science and Technology (NTNU) study, which reveals that hard training certainly impairs fertility in women.

How does weight affect fertility in men?

It must be reported here that being overweight also impairs fertility in men, causing problems in sperm number and morphology. It also causes erection problems and reduces the libido (sex drive).

Harvard researchers found that men who were overweight were likely to have lower sperm counts and perhaps have no sperm in their ejaculate.

Azoospermia in men due to excessive weight

Men with BMI over 30 were 80 percent more likely to have no sperm as compared to men in the normal BMI range.

Being underweight is also not good for male fertility as it adversely affects the sperm quality.

Can losing weight enhance your fertility?

Conditions like PCOS, insulin resistance, etc. are often a result of obesity and losing weight can actually help these hormonal problems. 

A recent study from the Stanford School of Medicine was able to show that significant weight loss helped women achieve higher pregnancy and live birth rates.

The good news is that obesity related infertility can be turned around by losing weight, and if this is your concern, you should discuss with your fertility specialist to see if your body weight is actually the reason for your fertility problems.

Age is also an important factor in fertility and you cannot delay fertility treatments forever, in the hope of losing weight and achieving the normal BMI.

If you are having trouble with conception, some common fertility tests may give you an indication of the underlying problem and certain lifestyle changes may help you through it.

Do you know of someone who is struggling to conceive because of too much or too little body weight? 

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