Energy Availability: Fueling Athletes for Health and Performance
Energy availability refers to the amount of energy left for the body’s needs after accounting for exercise. In simple terms, it’s the fuel athletes have available for bodily functions once training is done. If an athlete eats plenty to cover both training and daily living, energy availability stays high. But if intake doesn’t keep up with output, Low Energy Availability (LEA) can occur – meaning the athlete’s body doesn’t have enough energy to stay healthy and perform optimally.
Occasional short-term energy deficits (like after a hard training session) can be corrected with rest and proper nutrition. However, chronic Low Energy Availability – consistently not eating enough for the training load – can lead to serious health and performance problems.
This guide breaks down LEA and Relative Energy Deficiency in Sport (RED-S), warning signs to watch for, and what coaches can do (including when to involve a dietitian or doctor) to keep athletes healthy.
LEA vs. RED-S: What’s the Difference?
Low Energy Availability (LEA) is the underlying cause, it’s the state where an athlete’s energy intake is insufficient relative to what they burn through exercise. LEA can be intentional (e.g. an athlete deliberately dieting or skipping meals) or unintentional (simply not realising how much more fuel their increased training requires). In either case, if LEA persists, the body starts down-regulating essential functions to conserve energy, leading to broad consequences.
Relative Energy Deficiency in Sport (RED-S) is the syndrome of health and performance issues that results from prolonged LEA. In 2014, the International Olympic Committee introduced the RED-S concept to expand on the older “Female Athlete Triad” – recognising that energy deficiency affects all genders and numerous body systems. In women, LEA often causes disruptions in menstrual function (amenorrhea or irregular periods), and in men it can lead to suppressed testosterone and low libido. But RED-S goes beyond reproductive effects, encompassing multi-systemic impacts, from weakened bones and frequent injuries to impaired immunity, slowed metabolism, heart irregularities, and mood disturbances.
In short, LEA is the energy shortage, and RED-S is the collection of problems that arise when that shortage becomes chronic. The Female Athlete Triad (energy deficiency, menstrual issues, bone loss) is now considered a subset of RED-S, which includes those three and many other consequences in both female and male athletes.
Warning Signs of Inadequate Energy Availability
Coaches are on the front line to notice the red flags of LEA/RED-S. Often, the signs are subtle at first. Here are some common warning signs that an athlete may be under-fueled:
Persistent fatigue and declining performance: The athlete is always tired, lacks usual spark, or their performance is plateauing or worsening despite training. They may report feeling “drained” or have unusually poor workouts.
Frequent injuries or illness: Injuries such as stress fractures or overuse injuries occur more often, or the athlete keeps getting sick (colds, infections). LEA weakens bone health and immunity, so things like repeated bone stress injuries or constant illness can be a red flag.
Noticeable weight changes or stagnation: Significant weight loss (especially rapid) without trying, or failure to gain expected muscle/weight during growth phases. In younger athletes, not hitting expected weight/height milestones could indicate under-fueling. Conversely, some athletes with RED-S may appear normal in weight, so weight alone isn’t a perfect indicator – don’t ignore other signs even if weight looks “fine.”
Changes in menstrual function or libido: For female athletes, irregular or missing periods (amenorrhea) or delayed puberty are key warning signs of LEA. For male athletes, low libido, erectile dysfunction, or other signs of low testosterone (loss of morning erections, for example) can indicate energy deficiency. (Note: Athletes or coaches might overlook these signs, so it’s important to foster an environment where athletes feel comfortable reporting them.)
Mood and concentration problems: LEA can take a mental toll. Watch for increased irritability, depression, anxiety, difficulty focusing, or unusual apathy in an athlete. An athlete who was upbeat may become irritable or withdrawn. Similarly, trouble concentrating in school or sport strategy can stem from low energy availability.
Disordered eating behaviors: Be alert to an athlete becoming overly restrictive with food, obsessed with calories, or exhibiting odd eating habits (skipping team meals, avoiding whole food groups, etc.). Frequent comments about weight, body dissatisfaction, or excessive fear of “getting fat” are warning signs. Notice if an athlete is constantly dieting, or if you observe binge eating and purging behaviors – these may signal an eating disorder or disordered eating pattern contributing to LEA.
Other physical red flags: Feeling cold all the time (even in normal temperatures), unexplained hair loss, or digestive issues like constipation and bloating can all result from an under-fueled body slowing down its metabolism.
No single sign confirms RED-S, but a pattern of these signs should raise concern. Early detection is key: if you notice these issues, it’s time to take action (increase fueling, reduce training load, and/or seek medical guidance) before more serious damage occurs.
Coaching Strategies to Prevent and Address LEA/RED-S
Coaches play a pivotal role in both prevention and early intervention of low energy availability. Fostering a team culture that values health and smart fueling can protect athletes from RED-S. Below are actionable strategies for coaches, with steps to implement and ways to discuss energy availability with athletes:
Promote a Fuel-First Culture: Emphasise to athletes that food is fuel and is just as important as training. Discourage fad diets or training on an empty stomach. Encourage regular meals and snacks around training sessions so athletes constantly replenish energy. You can talk about nutrition in terms of performance – e.g. “eating enough carbohydrates and protein after practice will help your muscles recover and get stronger for the next session.” Make sure team travel and events include time for meals, and consider having healthy snacks available at practices or competitions.
Be Mindful with Weight and Body Talk: If weight or body composition must be discussed, do it privately and respectfully – never in front of the team. Avoid public weigh-ins or commenting on athletes’ bodies (positive or negative). Set safe standards for weight monitoring: for example, involve a dietitian for body composition testing and do it infrequently. Especially avoid frequent weigh-ins with younger athletes. Emphasise that performance and health, not a specific weight or look, are the priorities.
Focus on Health and Performance over Appearance: Continuously send the message that how an athlete performs and feels matters more than how they look. Praise effort, progress, strength, and skills – not leanness or body shape. Remind athletes that all body types can excel in sport and that looking “thin” doesn’t automatically mean better performance. This helps reduce pressure an athlete might feel to undereat.
Educate Athletes (and Staff) on RED-S: Proactively teach your team about the importance of fueling and the risks of energy deficiency. Many athletes (and even fellow coaches) simply don’t realise the harm LEA can cause. You might host a workshop with a sports dietitian or share articles/videos on RED-S. Key points to convey: adequate nutrition = better training adaptations, and chronic undereating can impair performance and cause long-term health issues. When athletes understand that eating well is part of their job as athletes, they’re more likely to fuel properly. Encourage questions and open conversation about nutrition.
Encourage Open Communication and Safe Reporting: Make it clear that athletes can come to you if they’re feeling overly fatigued, struggling with eating, or have concerns about their health. Normalise discussions about things like menstrual cycles for female athletes – for example, you might say, “Your period is a good indicator of whether you’re fueling enough. If it becomes irregular or missing, let’s connect you with the right person to talk about with.” Reinforce that no one will be punished for admitting they’re tired or need help; instead, you’ll work with them to find solutions. For male athletes, you might ask in general how their energy and recovery feel, since their signs can be harder to spot (they might not realise low morning energy or mood changes could be fuel-related). The goal is to catch issues early by creating a non-judgmental space for athletes to speak up.
Adjust Training When Needed: If you suspect an athlete is in a low energy state, consider modifying their training plan in the short term. This might mean reducing training volume/intensity or enforcing additional rest days while nutritional adjustments are made. Emphasise that rest and fuel will help them bounce back stronger. Monitor the athlete’s response – you should see improvements in energy and mood if LEA is being addressed. If not, that’s a sign the issue might be deeper and needs professional evaluation. Also, be vigilant that athletes aren’t doing extra unsupervised training on the side that you didn’t program; sometimes very driven athletes will add miles or sessions but not add calories, tipping into LEA. Encourage balance: “Train hard, but also recover hard.”
Build a Support Network: Coaches shouldn’t have to tackle RED-S alone. Proactively connect with sports dietitians, physicians, and mental health professionals who understand athlete energy needs. Establish a relationship with a local sports nutritionist who can give guidance on meal plans or come talk to the team. Know a sports medicine doctor or clinic you can refer athletes to if you spot serious signs. Let your athletes know that needing extra help is OK and part of reaching their best. By having experts to refer to, you can address issues more effectively – for example, a dietitian can create a personalised fueling plan, or a therapist can help if disordered eating is involved. This multidisciplinary approach is often the most effective way to get an athlete back on track.
Importantly, set the tone with your team culture. Celebrate proper fueling as a competitive advantage (“our squad stays fueled and strong”) and never shame athletes for eating. Likewise, model good behavior: avoid comments about your own or others’ bodies, and don’t glorify training through extreme fatigue. When athletes see their coach prioritising health, they’re more likely to follow suit.
Male vs. Female Athletes: Key Considerations
While any athlete can experience RED-S, there are some gender-related considerations worth noting (even as we emphasise that the core issue – not eating enough for your activity is not unique to one gender):
Female Athletes: Historically, the Female Athlete Triad highlighted women’s risk, especially signaled by menstrual disturbances. Menstrual regularity is a crucial health marker for female athletes. Coaches should treat a missing period or suddenly irregular cycle as a warning sign, not a normal adaptation to training. Encourage female athletes to view their period as an indicator of energy balance (sometimes called a “vital sign” for female athletes). If an athlete reports loss of her period (and isn’t on a form of birth control that affects cycles), you should respond by ensuring they get medical evaluation and adjusts her nutrition/training. Emphasise that amenorrhea is not a badge of honor for working hard – it’s a sign the body is under stress from under-fueling. On the positive side, also reinforce that eating enough and perhaps gaining a little weight can restore menstrual function and improve performance and bone health. This can be a sensitive topic, so approach it with care and privacy, e.g., “I’m not a doctor, but losing your period can happen when your body isn’t getting enough fuel. It’s important we loop in a medical professional so they can help you stay healthy and strong for competition.”
Male Athletes: Because men don’t have a menstrual cycle as an obvious indicator, RED-S in male athletes can fly under the radar longer. In fact, research suggests men might need to reach a more severe energy deficit before outward symptoms become evident. Coaches should be aware that male athletes also face energy deficiency risks – for example, male runners who restrict intake can suffer bone density loss, hormone disruptions (low testosterone), and performance decline. Keep an eye on markers like recurrent injuries or stagnating muscle gains in male athletes, and listen if they mention low sex drive or other health changes. When discussing fueling with male athletes, it may help to frame it around strength and recovery (“Eating enough will increase your power and help your muscles recover faster”). Make it clear that RED-S is not just a female issue – sometimes male athletes mistakenly think “that’s only a problem for female athletes” and therefore ignore the signs. By citing examples (e.g., share this article on Jake riley with your squad), you can drive home that proper fueling matters for everyone.
Bottom line: Both female and male athletes require adequate energy for optimal health. The manifestations might differ (for instance, women might stop menstruating, men’s testosterone might tank), but the solution is the same: restore energy balance. Coaches should foster this understanding in all athletes, regardless of gender.
Personal Energy Availability Questionnaire (PEAQ)
The Personal Energy Availability Questionnaire is a short, free tool designed to help athletes understand whether their current training and nutrition balance is supporting healthy performance. It screens for low energy availability and the risk of Relative Energy Deficiency in Sport (RED-s), which can affect anyone in athletics regardless of age, event group or training level.
What the PEAQ looks at
The questionnaire asks about training load, nutrition habits, physical changes, growth, injury patterns and, where relevant, hormone function. There are separate versions for male and female athletes. Once completed, the App provides a RED-s risk score and simple guidance to help athletes reflect on their current situation.
Why coaches might use it
The PEAQ gives athletes a chance to think about whether they are fuelling well enough for the demands of their sport. For coaches, it can act as a conversation starter to support a healthy training environment. It does not diagnose RED-s, but it can flag when athletes might benefit from checking in with a health professional.
How coaches can integrate it
- Invite athletes aged sixteen and over to complete the PEAQ at the start of a training phase.
- Use the results to support balanced messaging about fuelling, rest and long term development rather than performance pressure.
- Encourage athletes to complete the version appropriate to their sex, as the questions differ in focus and biological considerations.
- Remind athletes that the PEAQ is a guide only and does not replace medical advice when concerns arise.
When to Refer to a Dietitian or Doctor
One of the most critical roles for a coach is knowing when an athlete’s situation goes beyond the coach’s scope and needs professional evaluation and treatment. Escalate to a sports dietitian, physician, or other appropriate professional in the following scenarios:
Significant health red flags: If an athlete shows signs of a serious medical issue – for example, episodes of dizziness/fainting, an unusually low heart rate or blood pressure, or recurrent stress fractures – they need prompt medical assessment. These could indicate advanced RED-S that requires a doctor’s intervention (and possibly a temporary halt in training).
Diagnosed or suspected eating disorder: If you suspect an athlete is struggling with an eating disorder (e.g. anorexia, bulimia) or severe disordered eating behaviors, involve professionals immediately. This is beyond a coach’s area of practice. A physician can evaluate medical stability, and a therapist and dietitian will be key for treatment. Signs like rapidly dropping weight, evidence of purging, or extreme fear of weight gain are red-line indicators to seek expert help.
Prolonged or serious loss of menstrual cycle: For female athletes, missing two or more consecutive periods (or consistently irregular cycles over several months) warrants a medical referral. A gynaecologist or sports physician can check for underlying hormonal issues and guide the athlete on nutrition and hormone recovery. It’s important to remember that the coach’s role is not to track menstrual cycles, but rather to educate athletes on why regular cycles are a key sign of good health and adequate fuelling. Encourage athletes to monitor their own cycles privately and to report any changes they notice so that appropriate support can be arranged.
Notable hormone disruptions in male athletes: If lab tests or clinical signs suggest low testosterone in a male athlete (for instance, fatigue, decreased libido, depression, and poor recovery all together), a physician should be consulted. They can rule out other causes and confirm if energy deficiency is a likely culprit. Bone density scans might be indicated if stress fractures have occurred.
Significant weight change or stalled growth: If an athlete has lost a significant amount of weight rapidly (more than ~5% of body weight in a month) or a growing adolescent has stopped expected weight/height progression, bring in a dietitian and doctor. Such changes can have broad health implications. A dietitian can assess dietary intake and increase plan, while a doctor can check for any acute issues (like anemia, hormonal imbalance).
When in doubt or no improvement: If you’ve tried initial interventions – talking with the athlete, adjusting training, encouraging more fueling – and you still observe warning signs or no improvement, it’s time for professional help. For example, if fatigue and performance issues persist or worsen despite rest and nutrition tweaks, there may be deeper metabolic or psychological factors at play. It’s better to be cautious and get an expert evaluation rather than wait until the athlete’s condition is severe.
When referring, approach it as a supportive measure, not a punishment. Let the athlete know that seeking help is aimed at making them healthier and ultimately a better athlete. For instance: “I think it would be good to have you chat with a sports dietitian who can fine-tune your nutrition so you’re properly fueled,” or “Let’s have a doctor check things out, just to be safe – we want to get you back to feeling 100%.” Emphasise that you’ll continue to support them and that a team of experts is there to help them succeed safely.
Key Messages for Coaches
Fueling is fundamental. Adequate energy availability is non-negotiable for athlete health and peak performance. LEA and RED-S can affect any athlete, in any sport, male or female.
Know the signs. Fatigue, declining performance, injuries, mood changes, and (for females) menstrual irregularities are warning signs that should never be ignored. Early recognition allows for quick intervention.
Create a healthy culture. Coaches can prevent many problems by promoting a team culture that values nutrition, rest, and well-being over weight or appearance. Educate athletes about fueling and keep communication channels open.
Take action and refer when needed. If an athlete is under-fueling, intervene with adjustments and support. And if the issue is serious or persistent, don’t hesitate to involve a dietitian, doctor, or psychologist. A multidisciplinary approach ensures the athlete gets the comprehensive care they need.
