Weight and Fertility

By Rashmi Kudesia, MD

As a residual effect of human evolution millennia ago, the female reproductive system still takes its cues from the adrenal system, a parallel axis of metabolism, nutrition and energy. In its most extreme forms, during the severe bouts of stress and malnutrition encountered in war or famine, the brain determines that in the absence of reliable incoming nutrition, energy should not be expended on reproduction. Women stop having their period (retaining their blood and iron stores) and stop ovulating (preventing an untimely conception). With less severe alterations in overall energy stores, the effect is not necessarily as profound, but even a 5-10% change in body weight can impact menstruation and fertility.

There are a few key points to take away when we think about weight and fertility. First, the right weight (not too low, not too high) gives the highest chance of a regular ovulatory menstrual cycle. We typically use a normal body mass index or BMI (calculate yours below) as a rough guide.

But it’s not a perfect tool. Weight distribution (body types) can also influence our health, with the apple shape (abdominal fat) being most associated with health outcomes, such as pre-diabetes, type 2 diabetes and so forth. Being on either side of what your body considers “normal” can result in an abnormal or absent period. Though we can certainly induce ovulation with medication, at least moving the weight in the right direction is always advisable. Typically we’d at least like to see a BMI between 18.5 and 40 before starting fertility treatment, as being under- or overweight can not only interfere with ovulation, but also increase the miscarriage rate. Further, excess fat tissue not only interferes with ovulation, it also has a negative effect on egg quality, causing poorer embryo development, and can affect the endometrium, or lining of the uterus, where implantation occurs.

Secondly, there are studies to indicate that, when compared to fertile women, patients with unexplained infertility showed significant abnormalities in dietary habits. These differences range from a minimal imbalance in micronutrients, likely very amenable to with dietary supplementation, to the severe macro- and micronutrient deficiencies commonly seen with obesity. The latter could require long-term nutrition counseling and lifestyle modification to achieve health benefits. Indeed, the Academy of Nutrition & Dietetics holds the position that all women of reproductive age should receive education about the maternal and fetal risks of obesity, excessive weight gain during pregnancy, and post-partum weight retention (50% of women don’t lose their “baby weight”). Fertility centers, including ours, often have an on-staff nutritionist to help evaluate where you can make improvements, and almost all women could benefit from taking advantage of this opportunity.

Similarly, there is also data to show that not only do extreme athletes often experience absent periods, but women exercising at regular levels can experience subtle changes in their menstrual cycle that may be difficult to notice, but decrease fertility. Since exercise is definitely recommended for all women, including during the pre-conception and pregnant phases, it’s worth discussing with your physician whether your regimen is too lax, too intense or may be affecting fertility.

The good news is that weight-improvement interventions can result in relatively high spontaneous pregnancy rates, and fertility treatment can help most of the women still having difficulty. Furthermore, improving lifestyle is not only beneficial to fertility, but long-term health. This is an investment worth making! Creating a healthy lifestyle while growing your family can be a strong bonding and empowering experience for a couple, and for straight couples, being overweight or having an unhealthy lifestyle can certainly diminish male fertility as well.

We strongly encourage our patients to take stock and work with their care team to create a lifestyle plan that maximizes their health as relates to weight and nutrition. Often times, this includes identifying stress, anxiety or depressive forces that lead to less healthy choices, and our mental health team is definitely available to help explore these concerns. Don’t be afraid to bring up these questions in your next visit, and explore what aspects of your fertility care you can positively influence!


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