The best way to answer this question is to refer back to one of our favorite childhood fairy tales, “Goldilocks and the Three Bears”. Remember when sweet little Goldilocks was looking for a bed to sleep in and she found one that was “too soft”, one that was “too hard”, and, yes, ultimately one that was “just right”. The same goes for this question. Both obesity and extreme thinness can be associated with infertility. You need to be “just right” to conceive easily.
There are several reasons why very high or very low body fat can affect fertility. Fat tissue is involved in converting androgens (male hormones) to estrogen. Since body fat is a significant source of estrogen, it would seem logical to think that more body fat means more hormones and that that would be a good thing. Well, fertility requires a fine balance, and it really depends on the type of hormones that are around. If you are too thin, you make a form of estrogen that is too weak, but if you are too fat, the higher level of estrogen sends signals to the brain that affect your ability to stimulate the formation of eggs.
Now, we need to clarity exactly what “fat” means. In our society, there are crazy definitions of fat and thin. Magazines are littered with starving actresses and models who are thought to exemplify the ideal weight. Let us try to stop the insanity.
Body mass index (BMI) is a reliable indicator of total body fat and is the most commonly used measurement related to the risk of disease and death. It is calculated using the formula, BMI=kg/m2. Sound hard? There are many online calculators where you simply enter your weight and height and get your BMI. The score works for both men and women, but it does have some limitations. BMI may overestimate body fat in athletes or people who have a very muscular build. It also can underestimate body fat in older persons and those who have lost muscle mass. In general, a body mass index between 19 and 30 will keep you in the right range to have normal reproductive ability.
By Mark Leyner
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"Are fat women more fertile?" was posted on Monday, October 29th, 2007 at 12:58 am.