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Sinead Brophy Aug 16, 2020 12:00:00 PM 27 min read

Fuelling Female Performance - Part 1



Fuelling Female Performance


Ever have those periods of training where you just feel ‘meh’? Your energy is low, you can’t seem to add to your PBs, you have a recurring head cold that you can’t shake, and a niggly hip that just won't get better. What is going on?

You could be under-fuelled.

“Wait, wait, wait”, I hear you say. “That can’t be right, I eat like a horse/I eat my recommended three meals a day/I eat really healthily/etc”.

Nevertheless, not fuelling correctly is a common phenomenon amongst active women. A shocking 45% of recreational female* athletes are at risk of what is known as ‘Low-Energy-Availability’.

*recreational = training 3 or more times a week (yes, I am looking at you FFS Members and Crossfit athletes around the world).


In this two-part blog I am going to take you through the What, Why, and How of Low-Energy-Availability and how to fuel female performance. In part 1, I will cover ‘What is Low-Energy-Availability’ and Why it matters’. In part 2, I will cover ‘ ‘Why it happens’ and ‘How to fix it’.

Fuelling female performance image 1

Image source: Pexels

What is Low-Energy-Availability


What is it?

In simple terms, low-energy-availability (LEA) is underfuelling.

It is when an individual, normally an athlete (including recreational athletes - and yes, that means you and me) is in a chronic state of energy deficit. If you engage in purposeful activities/exercise, then you are an athlete.

This happens when our energy out is greater than our energy in. Nutrition science nerds read on; for anyone else, jump to Energy Balance below.


Energy Outputs

Our bodies have a number of energy requirements that we need throughout the day. Some of these are to support basic functions such as breathing, pumping blood around our body, whereas others are there to support our daily movement and energy.

We have our BMR (the basic amount of energy to support survival) the energy expended when eating and digesting food, and our non-exercise activity thermogenesis, which is a fancy way of saying our daily movements (shopping, cleaning, walking to work etc.)

Only after all of these basic functions are taken care of do we look at daily stressors which bump up our energy output, including purposeful exercise.


Energy Input:

This is more straightforward; it is the food that we eat and the liquids that we drink that provide us with our energy intake.


Energy Balance

Energy Input (EI) - Energy Output (EO) = Energy Balance

We want this to be neutral or in a slight surplus. If we are in a deficit, particularly a large deficit and for a long amount of time, this has negative consequences for our endocrine and reproductive systems, our bone health, our body composition goals, and our sports performance.

Women’s endocrine systems are particularly sensitive to a sudden large drop in energy balance, so if you are looking to lose body fat a smaller deficit over a longer period is recommended.


AKA Female Athlete Triad and RED-S

Low energy availability and it’s negative health and performance impacts is also referred to as Relative Energy Deficiency in Sport (RED-S), previously known as the Female Athlete Triad. We take a slight detour down sports-physiology memory lane to cover what FAT and RED-S are described as.


The Female Triad

You may have heard of the ‘female triad’ before. It was a condition that was recognised in female athletes that linked three of the following health conditions: eating disorder/disordered eating, reduction in bone density, and menstrual dysfunction (either loss of period or issues with cycle).


Normal BMI & Energy Deficiency

It is important to note that studies have shown that women can have the three criteria of the Female Athlete Triad even if they have a normal BMI and bodyfat. We often think of people suffering from underfuelling as being very lean, with low body fat but that isn’t always the case.

A study in 2015 looked at forty women from endurance teams and competitive clubs with normal or “healthy” BMI of 20 and body fat percentage of 20%, who were exercising between 7 - 15 hours a week (Melin et al, 2015). They found that:

  • 63% had low/reduced energy availability,
  • 25% an eating disorder,
  • 60% menstrual dysfunction,
  • 45% impaired bone health,
  • 23% had all three Triad conditions,

This shows the high prevalence of the female triad symptoms amongst women with low energy availability, despite having ‘normal’ BMIs.


Relative Energy Deficiency in Sport (RED-S)

In 2014, the International Olympic Committee expanded this definition to better encapsulate the “complexity involved and the fact that male athletes are also affected.”

RED-S syndrome refers to “impaired physiological function” including, but not limited to:


  • metabolic rate,
  • menstrual function,
  • bone
  • health,
  • immunity,
  • protein synthesis,
  • cardiovascular health


RED-S Mountjoy et al 2014
Source: Mountjoy et al (2014)

The IOC define the cause of RED-S as “energy deficiency relative to the balance between dietary energy intake and energy expenditure required for health and activities of daily living, growth and sporting activities.”

It is important to note that this updated definition removes the word ;female’ as RED-S can also impact men, their performance, and their testosterone levels. Secondly, it removes the word ‘eating disorder’. This is significant because LEA can often be unintentional due to poor nutrient timing, a lack of knowledge around fuelling or a misguided attempt to lose body fat.


Why it matters - Fuelling is key to performance & health


Ok, ok so physiology lesson over…..How do I know if I am underfuelling?

All of the reasons I mentioned above and some. Fatigued? Not hitting PBs? Sleep disrupted? Menstrual Cycle disrupted? Hair falling out? n you should really take a look at the amount that you expending and the amount that you are fuelling yourself.

Here is a great infographic from Girls Gone Strong with 12 signs that you could be underfuelling.


Image source: Girls Gone Strong Instagram


Impact of Underfuelling - putting your body in prioritisation mode


Being in a low energy availability state means that we are not consuming enough energy (food) to support our daily functions as well as daily stressors and our training. This means that our body’s balance gets out of whack and we are not able to get the adaptations that we want out of our training. Our body does not know the difference between a self-imposed and a real shortage of food and it has to prioritise what functions it wants to keep supporting.


Downregulation of RMR

When we are underfuelling our resting metabolic rate goes down. Our bodies adjust its metabolic functions so that it can survive on less. The results of this can take a long time to reverse and this is seen clearly in the Biggest Looser Study where, a number of years after they won, researchers compared Biggest Loser Winners to peers who were matched in age and fitness levels and found that their RMR was 800-1000 cals lower than their peers.

This means that day -to-day you burn less calories. Your body is smart and in a bid to conserve energy, it makes you fidget less, makes your fatigued, and down regulates other non-essential energy expending activities in a bid to conserve energy.


Reproductive System & Menstrual Disturbance

If we are underfuelling, our bodies don’t want to spend energy on growing a baby as this is an incredibly energy consuming job. If your body thinks it is in a time of shortage, it will prioritise supporting its own bodily functions and shut down the ability to reproduce. This can result in menstrual disturbances like a short luteal phase, irregular periods, or a complete stopping of your period, known as hypothalamic amenorrhea (HA).

SIDE NOTE : This is why it is incredibly important to track your period. Our cycles are our fifth vital sign and help us identify if we are not supporting our lives and exercise.

Williams et al (2019), found that 50% of exercising women had a subtle form of menstrual disturbance due to LEA and 30% of exercising women had more significant impacts, such as irregular periods or complete loss of their menstrual cycle.


Menstrual Disturbances due to Underfuelling

Image source: Author's own

This not only has fertility issues but impacts other essential areas of our health too; our reproductive hormones are incredibly important for bone density, heart health and mental health (which I cover below).


Other health areas:

In LEA we can feel cold as our bodies don’t waste energy trying to eat us up, we can feel fatigued all of the time, and our hair, nails, and skin can get dry/brittle and break easily.

Our performance is negatively impacted too (see below).


The Health Risks of Underfuelling and Losing your Period (HA)


We have to treat the menstrual cycle as a ‘fifth vital sign’. As Dr. Stacy Sims says, “if you don’t have a period, you are not a healthy athlete.’

Hypothalamic Amenorrhea (HA) or Functional hypothalamic amenorrhea is a the loss of your period due to the “suppression of the hypothalamic–pituitary–ovarian axis” and resulting “estrogen deficiency in young premenopausal women” due to “psychological stress, excessive exercise, disordered eating or a combination of these factors” (Shufelt et.al, 2017).

If you have lost your period due to HA, it means that your body does not have sufficient energy to prioritise your reproductive hormones which further reaching health implications beyond fertility:


Bone health & Osteoperosis

Oestrogen is very important for formation of new bone and replacing bone tissue. Progesterone is equally as essential for bone health as it retains on to the bone tissue that was formed and slows down its breakdown

One study estimated that the average bone mineral density (BMD) of a young woman with only six months of oestrogen deficiency is equivalent to that of a woman 51.2 years of age (Drinkwater, 1984).


Cardiovascular Disease

The link between CVD and HA is not as heavily researched due to the time frame of the study that is required. Nevertheless, there seems to be a commonality of low oestrogen between CVD in women and losing your period.

Oestrogen is important for the dilation of blood vessels as well as being an anti-inflammatory and reduces oxidative stress (Shufelt et al. 2017). In a study where pre-menopausal women had their ovaries removed (eg. surgical menopause) and did not get oestrogen replacement therapy had an 85% increased risk of CVD. (Rivera et al. 2009).


Decrease in Sports & Training Performance

Sports performance is, unsurprisingly, impacted by the suppression of our menstrual cycles to LEA.

As Ackerman points out in her article in the British Journal of Sports Medicine, “Chronic LEA (over many weeks to years) leading to RED-S can limit training adaptation and substantially increase injury risk” (Ackerman, 2020).

A study in 2014, looked at the impact of ovarian suppression (i.e. the loss of the athlete’s cycle) on their swimming performance (400m velocity). It found that not only was energy availability lower in those athletes without a menstrual cycle, but that their thyroid hormones, bone stimulating hormones, and 400m-velocity performance were negatively impacted over the 12-week training period. They concluded that it is essential to periodise nutrition and dietary intake to match and support increased training volumes (Vanheest, 2014).

So as you can see, none of this should be taken lightly. Whether you priority is health or sports performance or body composition, if you are underfuelling or restricting your calories too much, whether intentional or not, you are hindering your goals. You will end up chasing your tail, frustrated and potentially having a huge impact on your health.



Fuelling Female Performance - image 2

Image source: Pexels

Next week - Part 2


Next week, we will cover why underfuelling happens and how we can address it. Now that we have the back story and the context, we will dive deeper into the practical steps to ensure that you are fuelling your performance and goals and prioritising your health.


A parting word, LEA is a common cause of menstrual dysfunction and chronic fatigue, but it is not the only reason. Please make sure to speak to your health care provider to rule out any other issues, such as PCOS or thyroid dysfunction.



More Information


Sinead is passionate about female health and performance. She holds regular workshops on the topic of menstrual cycle health, fuelling female performance, and working in sync with your cycle, as well as working with 1:1 clients.

If you are interested in learning more, follow her instagram account dedicated to research backed information on how to work with your body, not against it - @gowiththeflow_workwithyourbody

If you would like to attend a workshop or work with Sinead, fill in this interest form or email her at sinead@ffs.ie




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Sinead Brophy

Coach Sinead is a certified Personal Trainer, Movement & Mobility Coach, Modern Pregnancy & Postnatal Exercise & Wellness Trainer, and is trained in Female Physiology and Nutrition. Sinead is particularly interested in the female athlete, from how the menstrual cycle impacts training to coaching women in strength and aerobic training during pregnancy. Sinead is leading the way in Dublin in educating women about how to work with their bodies, to harness the power of their hormones, and get the most out of their training. Sinead is heading up Small Group Personal Training for Pregnancy in the new FFS location across the road from the Rotunda, FFS Ivy Exchange Parnell Street - Dublin 1. Email Sinead at sinead@ffs.ie. Find Sinead on Instagram at @sineadbrophy