The Essential Role of Body Fat in Our Health – Part 4

By: Amber Whittemore RD, BSN, MHSc(c)

Welcome back to the series on the essential roles of body fat!

The previous blog posts on this subject were focussed on the roles our fat stores play in energy provision, maintaining our metabolism, immunity, as well as temperature! Today we will be focusing on how our body fat stores play a key role in our reproductive health.  Come back next week for more information on how our body fat promotes our bone, heart, and organ health!

Fat stores ensure adequate reproductive health

Body fat plays a key role in female fertility and menstruation

It has been long documented that women with a lower than recommended body fat percentage can experience a disruption in their reproductive ability1. One of the most common causes of this is known as “hypothalamic amenorrhea” – a condition that may occur with low body fat, body mass, and/or over-exercising.

Amenorrhea is the loss of menstrual periods for at least 3 months in women who were previously menstruating. Women’s bodies cannot menstruate below a certain body fat2; therefore, a low body fat can be one of the key reasons the hypothalamus, a gland in the brain which regulates body processes, slows or stops releasing the sex hormones that would typically signal menstruation each month3. Coupled with this is the impaired signalling for the body to produce estrogen, an essential hormone for human reproductive health, leading to the risk of estrogen deficiency. Estrogen is also a key hormone in maintaining our bone health, which we will get more into next week!

Women are less likely to get pregnant if they do not menstruate regularly2, although the infertility associated with hypothalamic amenorrhea is exacerbated with estrogen deficiency. This is because without adequate estrogen a woman’s ovaries cannot release nurtured eggs into the fallopian tube for fertilization4 – ultimately lending itself to infertility.

While this is reversible with resolving the cause of the amenorrhea and/or estrogen deficiency, untreated or prolonged hypothalamic amenorrhea can have long term consequences on reproductive health. Therefore, being mindful of the fact that having a healthy amount of body fat is essential for our reproductive and hormone health serves to protect women in the long run! 

Body fat and body mass index appear to also play a role in male fertility

While the subject of male fertility and low body fat/weight is largely understudied, there was one systematic review conducted in 2019 that did find an association between a low body mass index (BMI) and semen quality5. While BMI is not a direct measure of body fat, a low BMI is often associated with a low body fat percentage as well. This study suggested that men with a low body mass may be at a higher risk of male infertility, although more research is ultimately needed.

Body fat and a healthy body mass are essential for optimized and healthy pregnancies

Very few studies are dedicated to low body fat stores and the impacts on pregnancy, although there is research suggesting that women with a lower than recommended BMI have an increased chance of high-risk delivery4. A Low BMI is also directly related to an increased risk of miscarriage and pre-term delivery4.

Body fat and a healthy body mass assist in breastfeeding

Producing breastmilk takes a huge amount of energy, much of which comes from our fat stores6,7. The American College of Obstetrics and Gynecologists recommends that women who were considered to have a healthy pre-pregnancy BMI require an extra 450-500 calories per day to keep up with the energy needs of producing breastmilk for their infants6. Therefore, women with a low pre-pregnancy BMI, again – often associated with a low body fat, require more than an extra 500 calories daily to meet their bodies needs for breastmilk production! If unable to keep up with these requirements, milk supply will suffer6

The Bottom Line

While, unfortunately, this subject is largely understudied, it is clear that maintaining a healthy body fat percentage and BMI is absolutely essential for our reproductive and over-all health.

We hope you learned something from today’s blog, and don’t hesitate to reach out to a HEC Dietitian if you have any questions or concerns about your own health! Come back next week for a closer look at how our fat stores optimize our bone, heart, and organ health.


1Frisch, R. (1994). The right weight: Body fat, menarche and fertility. Proceedings of the Nutrition Society, 53(1), 113-129. doi:10.1079/PNS19940015

2Better Health Channel. (2020). Menstruation – athletic amenorrhoea. Received from:

3National Institutes of Health. (2017). What causes amenorrhea? Received from:

4Shufelt, C. L., Torbati, T., & Dutra, E. (2017). Hypothalamic Amenorrhea and the Long-Term Health Consequences. Seminars in reproductive medicine35(3), 256–262.

5Guo, D., Xu, M., Zhou, Q., Wu, C., Ju, R., & Dai, J. (2019). Is low body mass index a risk factor for semen quality? A PRISMA-compliant meta-analysis. Medicine98(32), e16677.

6Nurture Inc/Allison RD MS CDN. (2018). How much should you eat while breastfeeding? Received from:
7Mayo Clinic. (2021). Infant and toddler health: “I’ve heard that breast-feeding promotes weight loss. Is that true?”. Received from:,production%20and%20feed%20your%20baby.