How Do Weight Loss and
Exercise Affect Fertility?

By Gerda Endemann, PhD

June 23, 2022

Before women start fertility treatments, standard medical practice is to advise those with obesity to lose weight. This advice does not appear to be evidence-based and is likely a consequence of our society’s fat phobia. This advice does not appear to be evidence-based and is likely a consequence of our society’s fat phobia. Recent high-quality clinical trials have found that for women with obesity and unexplained infertility—when the reasons for infertility are not known—losing weight does not necessarily increase their chances of becoming pregnant.

In the FIT-PLESE clinical trial, rates of pregnancy were not affected by weight loss. Women with obesity and unexplained infertility were assigned to either four months of an exercise program or an exercise program plus a weight-loss diet. They then underwent three cycles of fertility treatments. There were as many healthy babies born to the women who only increased their physical activity as to those who also dieted and lost weight.

The senior investigator on the FIT-PLESE trial, Richard Legro, MD, FACOG, chair of the department of obstetrics and gynecology at Penn State, told me, “We went into this trial with the hypothesis that patients would do better, so it was surprising that losing weight might not help women to have a baby. Losing weight did result in overall health improvements. But there’s also potentially some harm: There was a trend toward increased pregnancy loss among the patients who lost weight.”

Legro added, “That suggests to me that we probably need to look at our recommendations a little more carefully for medical conditions like infertility and make sure that we’re not causing harm with blanket recommendations.” His hypothesis is that longer, more sustainable lifestyle programs may be beneficial; programs that avoid rapid weight loss followed by rebound weight gain. But Legro acknowledges that we don’t yet have evidence-based recommendations to make. “We do these trials because we don’t really know the answer. When you think you know the answer (and it is wrong) and don’t do the trial, then a lot of harm is done.”

What does seem to hold up as far as boosting fertility is physical activity. In several controlled trials, overweight women in an exercise program were twice as likely to have a baby as those not in an exercise program. And it may seem too good to be true, but when researchers reviewed results from four clinical trials, they concluded that exercise programs had been as effective as fertility treatments such as medications or in vitro fertilization. The benefits of physical activity were not restricted to women with unexplained infertility. Physical activity also boosted the numbers of pregnancies and babies for women with PCOS.

This article is for informational purposes only. It is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. To the extent that this article features the advice of physicians or medical practitioners, the views expressed are the views of the cited expert and do not necessarily represent the views of goop.