Over recent months, I’ve noticed a couple of research studies and articles that suggest low energy availability may be linked with 1) urinary leaking as a precursor to bone stress injury and 2) injury risk postpartum. And to me, this means 2 things:
- Proper fueling for women (whether they be post-natal or not) is important for long term bone & overall health
- Maybe the tide should be turning on “fat loss for mums/females” and conversations around post natal weight loss being the measure of success after having a baby
As someone who hit the postnatal period almost back to my pre pregnancy weight and continued to lose weight (and be more depleted) as I tried (unsuccessfully) to breastfeed my daughter. Whilst it sounds like I am giving myself a hard time, I’m not, I just have a better picture of my own mental and physical health as a new mum, now that my kids are older.
Here are summaries of the papers.
Low energy availability and menstrual health in military personnel
A groundbreaking study published in the British Journal of Sports Medicine has uncovered concerning findings about reproductive health in female trainees during intense physical training – and the results have major implications for any woman combining demanding exercise with insufficient fueling.
Unlike previous research that relied on self-reported menstrual cycles (which can be notoriously unreliable), researchers led by Kristin Popp at Boston Children’s Hospital took a much more accurate approach. They tracked daily hormone measurements from urine samples over 10 weeks in U.S. Army female trainees during Basic Combat Training, plus weekly blood samples to assess energy availability and stress markers.
The key take out
Even women reporting “normal” periods showed signs of reproductive dysfunction. The hormone testing revealed widespread suppression of the hypothalamic-pituitary-ovarian (HPO) axis – the system that controls ovulation and menstrual cycles. Most participants were missing the crucial progesterone surge needed for healthy ovulation.
Translation: Just because you’re getting a period doesn’t mean your reproductive system is functioning properly.
Why This Matters Beyond Fertility
Suppression of the HPO axis isn’t just about reproductive health – it’s a warning sign for several serious long-term health consequences:
- Bone health: Reduced estrogen leads to decreased bone density and higher fracture risk
- Cardiovascular health: Increased risk of heart disease
- Metabolic health: Disrupted hormone balance affects metabolism and recovery
- Injury risk: Poor recovery and weakened bones significantly increase injury susceptibilit
While the study focused on military training, the underlying mechanism – low energy availability (LEA) – is incredibly common in female athletes and gym-goers. LEA occurs when you’re not eating enough to support both your daily bodily functions AND your exercise demands.]
The researchers noted that beyond insufficient fueling, factors like:
- Elevated cortisol (stress hormone)
- Reduced sleep
- High training demands
…all contributed to reproductive dysfunction
Sound familiar? This combination is unfortunately common in women who are training hard while under-eating
Breastfeeding and injury risk - it there a link?
Why proper fuelling is important for active women
- Optimal performance and recovery
- Injury prevention through proper hormone balance
- Long-term health of your bones, heart, and reproductive system
- Accurate assessment of your reproductive health (periods alone aren’t enough)
The key takeaway? Your body needs enough energy to support both your training AND all your essential physiological functions. When it doesn’t get that energy, it starts shutting down “non-essential” systems – and reproductive health is often the first to go.
The REFUEL study (2019)
A study looking at menstrual cycle recovery for those who have RED-S (Relative Energy Deficiency in Sport) by Williams et al, 2019. This is the only study looking at the effect of increasing calorific intake whilst maintaining exercise expenditure for those having anovulatory cycles (no ovulation occurs – which means that pregnancy cannot occur). Menstrual cycle disruption, or lack of menstrual cycle is also a symptom of RED-S (Relative Energy Deficiency in Sport).
It can affect anyone who is under fueling and is particularly prevalent in those who also train with high intensity, without the fuel to support this level of training. Exercise is often the scapegoat with active females being told to exercise less or just do low impact, yoga or walking (especially if looking to conceive). However, it’s not that simple. This study helps move the conversation from “too much exercise is bad” to “are they fueling enough to fuel both training and reproduction?”
The REFUEL Study took university aged women who were regular exercisers, and who had lost their period. They continued to exercise and alongside this were given nutritional advice and support. For those who regained their period, they had an average intake of an additional 330 calories accompanied with an average weight gain of 5.7lbs.
I know you might read the words “weight gain” and recoil but it is often the difference that makes the difference to a return of a regular cycle.
Lower weight doesn’t equal better performance but being better fueled does (and helps recovery, sleep, mood too).
As someone who felt under pressure to look a certain way (and be at a certain and “random” weight) in my teens, twenties and even into my thirties, I can confirm that healing the relationship with my body (and food) has been the best move ever! More weight, more muscle, more energy, more joy!
About the author
Beth Davies is an experienced coach and personal trainer based in Leamington Spa. She works with women when they are in key phases of life transition; pregnancy, post baby and perimenopause. As well as those clients who are experiencing pelvic floor symptoms such as leaking, prolapse and pelvic pain. Beth creates coaching programmes which combine much needed education about female bodies, strength training, nutrition and gentle mindset work.
She has been featured in women’s lifestyle magazines and websites, including Stylist, Metro, Woman & Home and Marie Claire UK
Beth’s personal training and coaching for women provides face-to-face personal training in Leamington Spa, Warwickshire, and online across the UK and Europe.