Does Obesity Really Cause Infertility?


It’s hard to escape the fact that America has an obesity epidemic. Regarding women, there is an ever-increasing understanding of the correlation between obesity and infertility. It has been commonly hypothesize that obesity causes infertility but a recent study by Penn State researchers rejects that.
In 2007, Dodson’s own recent research at the Penn State Hershey College of Medicine confirmed that obese women undergoing infertility treatments needed higher doses of infertility drugs than normal-weight or overweight women.
“What we once held as dogma is now starting to fall apart,” he says. “We thought that if a woman’s obesity was not affecting her ovulatory function, her fertility would be similar to a normal-weight woman’s. But this does not appear to be true.” Studies like these led to the hypothesis that obesity must be associated with infertility. One study I found interesting was Van der Steeg’s and his colleagues.

  • They followed 3,029 couples who were having trouble conceiving on their own.

  • All the couples had spent a year or more trying to conceive, and none had obvious reasons for fertility problems — the women were ovulating and had at least one functioning fallopian tube, and the men had normal semen analyses.

  • The couples were followed until pregnancy was achieved or until they started fertility treatments. In addition to a fertility history, the women’s weight, height, and smoking status were measured at study entry.

  • The women were classified as underweight, normal weight, overweight, or obese based on their body mass index (BMI).

  • As measured by the BMI, a 5-foot 6-inch woman who weighs 115 to 154 pounds is considered normal weight (BMI of 18.5 to 24.9). If she weighs between 155 to 185 pounds she is considered overweight (BMI of 25 to 29.9), and she would be considered obese at a weight of 186 or more (BMI of 30+).

  • 10% were obese, with BMIs of 30 or more. These women had the most trouble conceiving during the yearlong observation.

  • For example, a woman with a BMI of 35 was found to be 26% less likely to achieve a spontaneous pregnancy than women who were normal weight or overweight but not obese.

  • A woman with a BMI of 40 or more was 43% less likely to get pregnant.


Initially, I read the article and I believed it and didn’t analyze it. But I’m really starting to think critically about everything I read. As I re-read the results I noticed a big limitation in this study. The frequency of intercourse was not taken into account. I’m no scientist but I think it can be commonly agreed that obesity can lead to more stress and less desire to have sex. So , sex definitely has to be factor to why normal weight women are 43% more likely to get pregnant. And how about the weight and health of the men?… Do you guys notice any other discrepancies with this study?

infertility4.jpeg A very recent study by the Penn State College of Medicine researchers followed 29 morbidly obese women for two years after gastric bypass surgery. I couldn’t find the paper or details on the study. The results were that the “effects of weight loss on reproductive function are more modest than hypothesized. In terms of ovulation, there doesn’t appear to be improvement after surgery. Other factors may be involved with infertility in obese women, such as diminished sexual desire and thus less intercourse.”
Maybe this study should have also included a third group, of normal weight women as well.


Personally, I believe that obesity isn’t directly correlated to infertility because there are many other confounding variables such as a reduced sex life and maybe it is more common for obese women to be with obese men making it even more difficult to get pregnant. It goes without saying that obesity is unhealthy and it can raise the risks for practically every health problem but I don’t think obesity really causes infertility. What do you guys think?


I never really took the possibility of obesity being a factor in infertility. However, after reading your blog I vaguely remembered hearing that people that increased obesity affects a woman's menstrual cycle. After some further research I found that an obese woman produces too much estrogen because of the abnormal amount of fat cells she has. This tricks the body into thinking it is pregnant and will stop the ovaries from producing estrogen. Since the body experiences irregular periods, I would think that this has a huge thing to do with infertility in obese women.

I think that your weight can effect your ability to get pregnant. Doctors constantly tell women who are trying to conceive that they should look at their diets. Some people go so far as to go on to the "fertility diet". This consists of decreased alcohol consumption, caffeine consumption, increasing your iron consumption and many other restrictions. Possibly the link between the obsess and infertility is not their weight rather than their diet. Proper nutrition does not guarantee conception but it can increase fertility.

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