Many of us are bombarded with diet trends popping up in our social feeds promising “amazing weight loss”. So many of these recommendations are made for weight change, but not optimal performance or long-term sustainable change.
Eating 1200 calories a day may cause weight loss, but it’s far below what most of us need just to function at rest. Add training, movement, and digestion, and the body is forced to adapt in ways that aren’t supportive of performance.
Relative Energy Deficiency in Sport
Relative Energy Deficiency in Sport (RED-S) is the collection of symptoms and conditions, felt by both males and females, as a result of being in a state of Low Energy Availability (LEA). LEA is a mismatch between how much energy you’re consuming through food and how much energy you’re using during your training. When we are not eating enough to meet the demands of training, our body is forced to adapt.
Our brain’s control centre, the Hypothalamus, senses the low energy levels and decides to conserve energy wherever it can. This means reducing some of the functions of your body, reducing or pausing their function in an attempt to have enough energy available for your training.
Like the dimmer you use for lights, things like your fertility (menstrual cycle for girls and testosterone for boys) is compromised, your gut function is reduced, and your metabolism is suppressed (lowered).
Health Impacts
Your metabolism
The minimum amount of energy that our body uses each day just to run (our RMR) is based on lots of individual things like gender, muscle mass, overall weight and height. What we see in individuals experiencing RED-S is a lowering of this metabolism to below where it should be. e.g. you may be predicted to have an RMR of 1500 calories per day. However due to your body ‘dimming’ lots of processes (fertility, gut, heart), we may see this be much lower than this.
As you can imagine, a suppressed metabolism is not all that fun. It makes you feel pretty blah, low in energy, struggling in training and can impact our ability to change body composition.
Suppressed hormones
There is this fascinating interconnected pathway of hormones in our body, all feeding back on each other between the Hypothalamus (brain), Pituitary (brain) and Adrenal Glands (on top of kidneys). When energy intake drops, oestrogen and progesterone levels fall in females and testosterone levels fall in males.
For females, this is often easy to spot – cycles may become longer or stop altogether.
For men, it is a little less obvious and instead may appear as reduced performance and a lower libido / sex drive.
Low energy availability disrupts more than just sex hormones. We also see an increase in the hunger hormone (ghrelin) and a decrease in the fullness hormone (leptin) – your body’s clever way of encouraging you to eat more.
Menstrual cycle
As mentioned, the hypothalamus is your control centre. When it stops being the metronome for hormone production for the menstrual cycle, we see the cycle stop. This can appear in a few different ways:
Primary Amenorrhea: This is when you are late to get your first period – 15 years or older.
Secondary Amenorrhea: This is when you have had your period, but it has now paused for three months or more. This may happen when low energy availability suppresses hormone production, but conditions like PCOS or high stress can cause similar changes, so it’s important to explore other factors with a GP.
Oligomenorrhea: This is where your cycle is present, but it lasts longer than 35 days.
For more info on how your menstrual cycle works check out our series here.
Bone
When energy availability is low, hormonal changes lead to increased bone breakdown and a reduced ability to form new bone. Over time, this results in weakened bone strength (osteopenia) and, in more severe cases, osteoporosis – significantly increasing the risk of stress fractures and long-term health issues.
Blood and Iron
This is more of a chicken or the egg scenario. RED-S can lead to iron deficiency, while an iron deficiency can also lead to RED-S. If you are eating less than you need, your intake of high iron foods may be low. As well as this, low iron count can lead to increased fatigue and shift our body’s ability to use energy. Iron is an essential part in transporting oxygen, so for both health and your performance, it requires some attention ASAP.
Immune Function
This is another example of the body turning down its “dimmer switch.” Keeping your immune system running well uses a lot of energy, so it’s one of the first things the body conserves. If you’re frequently getting sick, particularly with things like the common cold, then this is something to pay attention to.
Gastrointestinal
To save energy, the body slows down gut function, leaving digestion feeling slow and sluggish. As a result, the risk of symptoms like constipation and bloating can be common with RED-S.
Psychological
Here’s another chicken or the egg. Your psychological predisposition may lead to altered eating patterns and therefore sub-optimal intakes. On the other hand, being in LEA can lead to lower moods, difficulties managing stress or even depression.
Disordered eating and eating disorders
RED-S can occur in everyone, not just those who are ‘thin’. In fact, LEA is often accidental and a result of disordered eating practices.
What about Performance?
Studies show that RED-S reduces muscle glycogen, the primary fuel source for both intermittent and endurance exercise (1). There is also a reduction in muscle building processes which can affect both overall lean mass and your ability to recover. Finally, you’re also at a much higher risk of injury and stress fractures due to altered bone density, impaired decision making or delayed recovery.
Prevention
When you’re training at a high load, relying only on “clean” foods often won’t give you the energy you need to keep up and recover well. Particularly in developing athletes with a high training load, there needs to be a move away from always wanting to eat healthily. Sometimes we need to pull back on our greens and simply down a couple of doughnuts.
However, it’s not always as simple as adding more in. When going through this process, it’s preferable to have someone who knows what they’re doing so that you are making changes gradually. If your RMR is lower than it should be, increasing your intake all of a sudden will lead to a blip in weight which is the delay between your RMR at its lowest point and its normal point. It is normal to see these fluctuations in weight. Remember, this will eventually correct itself.
Where to From Here?
If you’re noticing changes in your energy, recovery, or mood – or unsure you’re fuelling enough, you don’t have to navigate it alone.
At Compeat, we help athletes understand their bodies, rebuild energy availability, and create sustainable fuelling habits that support both performance and long-term health. It’s not about perfection – it’s about clarity, confidence, and feeling like yourself again.
If you’re seeking guidance or want to explore your next steps, you can connect with our team or get started through the Compeat app. We’re here to meet you exactly where you’re at.
References:
- Cabre HE, Moore SR, Smith-Ryan AE, Hackney AC. Relative Energy Deficiency in Sport (RED-S): Scientific, Clinical, and Practical Implications for the Female Athlete. Dtsch Z Sportmed. 2022;73(7):225-234. doi: 10.5960/dzsm.2022.546. Epub 2022 Nov 1. PMID: 36479178; PMCID: PMC9724109.
