Telling Women to Lose Weight Doesn’t Improve Fertility, Study Finds

Doctors often advise women considered overweight by medical standards to lose weight before trying to have a baby, even though there is insufficient evidence to support this advice.

A randomized trial published in OLP Medicine found that women with clinically definite obesity and unexplained infertility who lost weight before starting fertility treatments were no more likely to conceive or have improved pregnancy outcomes than those who did not. weren’t losing weight.

In the scientific literature, obesity has been correlated with difficulty conceiving, pregnancy complications, and miscarriage, among other conditions that can affect your health (and the baby’s). But it is important to note that correlation is not synonymous with causation: some studies indicate that losing weight is not necessary; limiting calories can lead to pregnancy loss, while bariatric surgery has been linked to an increase in premature births or a smaller baby.

For the purposes of this article, we have used the terms “overweight” and “obese” in a medical context. The World Health Organization considers anyone with a body mass index (BMI) of 25 kg/m2 and over as “overweight”, and a BMI over 30 is called “obese”.

It should also be emphasized that BMI is a faulty measure: it does not provide an accurate picture of health, as it does not take into account biological or genetic differences that must be taken into account when considering is about distribution. of muscle and fat and the corresponding disease risk. This is just one reason why recommending weight loss before starting fertility treatments may not be helpful when relying on BMI – a higher BMI does not necessarily mean bad health.

Weight loss and fertility assessment

In the study, Richard Legro, MD, professor and chairman of the Department of Obstetrics and Gynecology at Penn State Health Milton S. Hershey Medical Center, examined more than 300 women with obesity and unexplained infertility. The team wanted to see if losing weight before trying to conceive via fertility treatments would increase their chances of having a healthy baby.

All the women had a BMI greater than 30 kg/m2. They ovulated regularly but had at least a year of unexplained infertility. The team did not include women with polycystic ovary syndrome (PCOS) or those who did not release eggs during their menstrual cycles.

They organized the women into two groups: Over the course of 16 weeks, the first group followed a diet, took weight-loss drugs, and exercised; the second group simply increased their exercise. After that, the women started three cycles of fertility therapy consisting of ovarian stimulation and intrauterine insemination (IUI).

Ultimately, the scientists found no significant differences in the number of healthy pregnancies and births between the two groups. Those in the first group (guided weight loss) lost 7% of their body weight; the women in the second group did not lose a significant amount.

The authors state that there was no improvement in live birth or healthy live birth rates among women considered obese or overweight who underwent weight loss intervention before starting the fertility treatments.

“We did not find an increase in conception rates with or without fertility treatment in women who lost weight,” says Dr. Legro. Kindergarten. “There is no strong evidence to recommend preconception weight loss in obese women with unexplained infertility,” the report states. In a statement, Legro acknowledges that the guidance differs from current clinical care standards.

Study limitations

Barry Witt, MD, medical director of WINFertility and a reproductive endocrinologist and Connecticut OB/GYN who was unaffiliated with the research, says Kindergarten that the The conclusion that weight loss is not beneficial cannot be generalized because the study patients had unexplained fertility. The research did not include patients with ovulation dysfunction. Additionally, the fertility treatment used — intrauterine insemination (IUI) with clomiphene — has a relatively low success rate, Dr. Witt notes. It can’t be compared to in vitro fertilization (IVF), where the success rates are two to three times higher, he says.

“Weight loss was 7% on average, so it’s possible that a greater amount of weight loss is needed to see a significant benefit,” adds Dr. Witt.

Is weight loss beneficial for fertility?

Losing weight before you conceive may have other benefits, however, researchers say. For example, some of the women who lost weight also lowered their blood pressure and decreased their waist circumference, two markers associated with long-term health and the prevention of chronic disease.

So should you try to lose weight before TTC? Talk to your doctor, advises Nithya Gopal, MD, an OB/GYN in New York who was not part of the study team.

“Not all women need to lose weight before they conceive – the number on the scale isn’t everything,” says Dr. Gopal.

“Instead, one should meet with their doctor to check factors such as blood pressure, overall cardiovascular health and a balanced diet before conception, either naturally or through fertility treatments,” she advises. . Health is made up of many different factors, not just weight.

That said, Dr. Gopal finds in his experience that patients who achieve what is considered a normal BMI (the US Centers for Disease Control and Prevention say this is when your BMI is between 18.5 and 24.9) before conception have lower rates of diabetes, high blood pressure, superimposed preeclampsia, and large fetuses that can contribute to labor complications.

“These are major factors that play a central role in the high or low risk nature of pregnancy, which ultimately have a huge bearing on the health of the placenta and the newborn,” Dr. Gopal told Motherly.

Eliminate weight stigma

Why is this study important? Because it helps start a conversation about eliminating weight stigma in a clinical setting.

Weight stigma is a common and well-documented problem in the medical world. It may be a weight bias, such as having ill-fitting medical gowns or blood pressure cuffs that are only suitable for thinner people. Some physicians may view overweight or obese patients differently (perhaps as lazy or boring), when in reality, weight issues may be beyond their control – weight often depends on genetics and certain socio-economic factors. economic.

On the other hand, some patients may avoid seeking health care due to a negative weight-related experience in the past. It gets more complicated during pregnancy, when they need care.

Related: ‘Don’t Weigh Me’ Cards Help Empower Patients in the Doctor’s Office

Anna Bohnengel, RD, a fertility nutritionist from Oregon, advises women to focus on health metrics other than weight loss, such as blood sugar control, antioxidant-rich diets, avoidance of endocrine disruptors environment and stress management.

According to Bohnengel, the most common barrier to fertility is that women don’t eat enough, especially nutrient-dense foods.

“Focusing on weight loss is often not helpful because when that’s the focus, women run the risk of starving and undernourishment,” she says. This can put the body in a state of stress, alerting that it is not safe to reproduce. She also notes the known harms of obesity on pregnancy.

“I recommend that a woman focus on the markers of health and a healthy lifestyle, rather than the number on the scale. That goes for whatever path she takes to become a mother,” says Bohnengel.


Forum E, et al. Weight loss before conception: a systematic review of the literature. Food and nutrition research. 2013. doi:10.3402/fnr.v57i0.20522

Legro R, et al. Preconception lifestyle intervention effects in obese infertile women: the FIT-PLESE randomized controlled trial. PLOS One. 2022. doi:10.1371/journal.pmed.1003883

Sakers, A, et al. Adipose tissue plasticity in health and disease. Cell Press. 2022. Doi: 10.1016/j.cell.2021.12.016

Silvestris E, et al. Obesity as a disruptor of female fertility. Reproductive Biology and Endocrinology: RB&E. 2018. doi:10.1186/s12958-018-0336-z

Wise, L, et al. A prospective, internet-based study of body size and time to pregnancy. human reproduction. 2010. DOI: 10.1093/humrep/dep360

Featured Experts

Anna Bohnengel, MS, RD, Oregon-based fertility nutritionist.
Nithya Gopal, MD, OB/GYN based in New York.
Richard Legro, MD, professor and director of the Department of Obstetrics and Gynecology at Penn State Health Milton S. Hershey Medical Center.
Barry Witt, MD, Medical Director of WINFertility and a Connecticut-based reproductive endocrinologist and OB/GYN.

nutrition, health

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