[Research Rundown] Running on Empty: Low Energy Availability in Male Endurance Runners
- May 1
- 26 min read
Imagine you're a dedicated recreational runner guy. You're probably not winning your hometown marathon, but you enjoy running and racing, and dedicate a lot of time and energy to it. You like the structure and the discipline of endurance training. You might even like (or at least tolerate) lifting in the gym a few times a week. You like that you get out of training what you put in. You like hitting new performance goals, and you like the challenge of chasing them.
And sure, you've been paying a little more attention to your food recently. After all, those few extra pounds are only going to slow you down in the pursuit of your goals. You get your protein, you make healthy choices, you've even starting taking a couple gels with you on your long runs recently because you've definitely noticed it helps you perform better. OK, so you wake up so early to get your runs in that you don't have time to eat anything before you head out (NBD, right? You usually feel fine... usually). And yeah, once you get home, it's full-on Morning Mode getting everyone out the door to school, to work. And besides, you aren't even that hungry during the day anyways.
And now... you've hit a slump you can't quite explain. You're coming off an exciting PR, and have even bigger goals for this next training cycle... but something doesn't feel right. You're experiencing more frequent muscle soreness, your sleep has taken a nosedive, your workouts are going... OK (not great). You're picking up a small injury here, a minor illness there, and you can't quite seem to stay healthy. You put your head down, and ignore it. After all, you're a busy guy with a lot going on, and not exactly getting any younger. Maybe it's just bad luck, or the "new normal", or maybe you just need to toughen up, yeah?
As a coach, I've seen a version of this scenario play out more times that I can count with the male runners I've worked with. What is going on here?
It could be low energy availability (LEA). A recent review of research on male endurance athletes sheds light on how chronic underfueling can wreak havoc on the body and mind, and today we're going to talk about those findings and explain why eating enough is just as important as training hard. We’ll explore what LEA is, how it affects men’s physiology (from hormones like testosterone to bone health and metabolism), the psychological toll it can take, and how this issue fits into the broader concept of Relative Energy Deficiency in Sport (RED-S). I want to empower endurance runners and coaches with knowledge about LEA – helping you recognize the warning signs and take action, so you can stay healthy and perform at your best.
What Is Low Energy Availability (LEA)?
Low Energy Availability (LEA) occurs when an athlete’s energy intake (calories from food) is insufficient to cover both their exercise energy expenditure and the energy needs of basic bodily functions. In simple terms, after a workout, there aren’t enough calories “left over” to support normal physiology; that's LEA.
Energy availability (EA) is typically defined by the formula:
EA = (Dietary Energy Intake – Exercise Energy Expenditure) / Fat-Free Mass
This value, measured in kcal per kg of lean body mass, reflects how much energy is available to keep the body running after accounting for training. LEA is usually considered to occur below a certain threshold – historically around 30 kcal per kg of fat-free mass per day. Research in female athletes found that dropping below ~30 kcal/kg FFM for even a short time (just five days) disrupted multiple hormonal and metabolic functions.
An athlete could be in weight balance (calories in roughly equal calories out) yet still have low energy availability if most of their calories are being burned in exercise rather than supporting normal physiology
In that scenario, athletes experienced elevated cortisol (a stress hormone) and decreases in crucial hormones like triiodothyronine (T₃, a thyroid hormone) and luteinizing hormone (LH, which affects reproductive function), along with reduced markers of bone formation and low blood glucose. In other words, within days of severe energy shortfall, the body starts downregulating important processes – a clear sign that it’s not getting enough fuel.
It’s important to note that energy availability is not the same as energy balance. An athlete could be in weight balance (calories in roughly equal calories out) yet still have low energy availability if most of their calories are being burned in exercise rather than supporting normal physiology. As physiologist Dr. Anne Loucks famously explained, the body can adjust to chronic energy deficiency by reducing its overall energy expenditure – essentially entering a conservation mode by downregulating how much energy you spend – so the athlete’s weight might stabilize, even though they are still underfueling . This means a runner could be weight-stable for weeks and months and not “skin-and-bones”, yet still be in a state of LEA and suffering its hidden effects.
How does LEA happen? Sometimes LEA is intentional – for example, intentionally restricting calories to lose weight or maintain a specific physique. Other times (and anecdotally, what I see most commonly), LEA occurs unintentionally, typically through a combination of 1) lack of knowledge about nutrition for your needs, 2) limited time to prepare or eat meals, 3) beliefs around specific types of foods that limit what you include in your diet, 4) beliefs around not needing to fuel around or during your workouts (or races) because you usually feel fine without it, and/or 5) an over-reliance on hunger cues, which can be blunted by exercise.
Whether due to conscious dieting or these unintentional factors, the consequences are the same: if you consistently fail to meet your energy needs, your body will be forced to compensate (and no, this is not a good thing).
From Female Athlete Triad to RED-S: LEA in Male Athletes
Sports science has recognized for decades that inadequate fueling is dangerous, but for a long time the spotlight was mostly on women. The classic Female Athlete Triad – defined as the interrelated problems of energy deficiency, menstrual dysfunction, and low bone density – was identified in female athletes and became a focus of research and education starting in the 1980s.
Men, however, were largely left out of the discussion. Men don’t have a menstrual cycle to serve as a clear warning sign of energy shortfall, and there was a lingering misconception that male athletes were immune to these issues. This has changed in recent years. In 2014, the International Olympic Committee introduced the term Relative Energy Deficiency in Sport (RED-S) to encompass a broader syndrome affecting athletes of any gender. RED-S describes the myriad health and performance consequences that arise from low energy availability, extending beyond the triad to include impacts on metabolic rate, immunity, protein synthesis, cardiovascular and psychological health, among other systems.
In 2018, an updated IOC consensus further solidified that RED-S is a concern for male athletes as well as females. Around the same time, researchers with the American College of Sports Medicine (ACSM) and the Female Athlete Triad Coalition began examining a “Male Athlete Triad.” In 2019 and 2021, expert panels concluded that men indeed experience triad-like interconnections between energy availability, bone health, and reproductive hormones. In men, the trio of LEA, hypogonadism (low testosterone), and impaired bone health mirrors the female triad (where menstrual dysfunction is the equivalent of male hypogonadism). A 2021 consensus statement formally defined this male triad and its scientific basis, underscoring that the male-specific signs were being taken seriously at last.
A male runner could be in a prolonged energy-deficient state without any single red flag. Low sex hormone levels in men can be tricky to recognize – changes in libido or mood are subtle and often attributed to training stress, and many men won’t know their testosterone is low unless they get a blood test.
One of the challenges for detecting LEA in male athletes is the lack of an obvious clinical signal like missed periods. A male runner could be in a prolonged energy-deficient state without any single red flag. Low sex hormone levels in men can be tricky to recognize – changes in libido or mood are subtle and often attributed to training stress, and many men won’t know their testosterone is low unless they get a blood test. Indeed, the prevalence of exercise-related low testosterone (sometimes called exercise hypogonadal male condition, or EHMC) is not well understood in part because it’s harder to identify than menstrual disturbances in women. Men might chalk up fatigue and poor performance to overtraining or aging, not realizing these can be symptoms of an energy deficit.
Crucially, if an athlete’s fatigue and hormonal issues are caused by low energy availability, the solution is very different than if it were “just” overtraining. Overtraining syndrome is typically addressed by reducing training load and increasing rest. However, if the underlying cause is inadequate fueling, then increasing calorie intake is the real key to recovery. Sports medicine experts emphasize ruling out LEA/RED-S when an athlete shows signs of overtraining. If an athlete is simply not eating enough to support his workload, his condition falls under RED-S rather than true overtraining, and needs to be corrected with nutrition.
The “Hungry Runner” – A Common Pattern
Many male endurance athletes unknowingly fall into LEA because of the demands of their sport. High-volume training burns an enormous number of calories, and without careful dietary planning, it’s easy to remain in deficit.
Studies show that endurance athletes, especially in sports emphasizing leanness (like distance running and cycling), often fail to eat enough to meet their energy needs. One survey of elite male and female athletes in various sports found over half of them had energy availability below the 30 kcal/kg threshold. In that study (which included endurance athletes), the majority also weren’t getting enough carbohydrates – a critical dietary component – and those in leanness-focused sports were chronically dieting or under-eating year-roundncbi.nlm.nih.gov. Even at the highest levels of our sport, underfueling is common: an 8-year nutrition study of 419 elite Dutch athletes reported that most athletes in all disciplines consumed inadequate carbs, and those in endurance and weight-sensitive sports engaged in persistent energy restriction. ncbi.nlm.nih.gov.
Disordered eating and body image issues, traditionally associated more with female athletes, are prevalent among male athletes too. The review notes that male athletes may strive for a certain weight or body fat percentage in hopes of improving performance or aesthetics, sometimes leading to dangerous behaviors.
Even short of full-blown eating disorders, many men exhibit disordered eating patterns. In one study of elite male cyclists, 57% had abnormal scores on the Eating Attitudes Test (EAT-26), indicating unhealthy food attitudes. Another study of competitive male cyclists found 67% were dissatisfied with their weight, 41% actively dieted to lose weight, and some resorted to extreme measures like laxatives or extra training sessions to shed pounds. Clearly, the pressure to be lean can push male endurance athletes toward chronically low energy intake.
The important takeaway is that male athletes are just as susceptible to LEA and its risks as female athletes, even if the manifestations differ. Being male doesn’t grant immunity from the laws of energy balance. Next, we’ll delve into what those consequences look like – physiologically and psychologically – for men.
Physiological Consequences of LEA in Men
Failing to eat enough has wide-ranging impacts on a man’s body, many of which directly undermine athletic performance and long-term health. Here are some of the key physiological consequences identified:
Hormonal Disruptions (Low Testosterone and Beyond): Perhaps the most significant effect of chronic energy deficit in men is on the reproductive hormone testosterone. Endurance training already tends to lower testosterone levels compared to sedentary individuals and when intense training is combined with inadequate caloric intake, testosterone can plummet. Researchers have observed that male endurance athletes often have testosterone concentrations at only 55–85% of the levels seen in non-athletic men. In one study, middle- and long-distance runners with clinically low energy availability had markedly reduced testosterone compared to their well-fueled counterparts. Another investigation found that among elite long-distance runners, those who averaged ~81 km (50 miles) per week had significantly lower total testosterone (around 9.2 nmol/L) than less active men (16.2 nmol/L), and not surprisingly, the runners also had much lower energy availability (27 vs 45 kcal/kg FFM). Over years of heavy endurance training, this effect accumulates – five or more years of running was associated with a ~30% reduction in testosterone levels compared to athletes with fewer years of training.
Lower testosterone in male athletes isn’t just a trivial number on a lab test; it has real consequences. Testosterone is a critical hormone for men’s muscular development, bone maintenance, red blood cell production, and libido. It helps increase muscle protein synthesis, builds hemoglobin (which carries oxygen in the blood), and supports aerobic capacity. When energy availability is low, the resulting testosterone suppression can lead to decreased muscle mass or inability to gain muscle, weaker bones, and even anemia-like effects due to reduced erythropoiesis (red blood cell formation). Athletes might notice a drop in strength, poorer recovery after workouts, or stagnation in fitness improvements – all tied to this hormonal shortfall.
Additionally, low libido and sexual function can occur; in fact, scientists have coined the term Exercise Hypogonadal Male Condition (EHMC) to describe endurance-trained men with chronically low testosterone and corresponding symptomsncbi.nlm.nih.gov. This state is thought to be an adaptive response (the body prioritizing survival over reproduction when energy is scarce) – similar to how female athletes lose their menstrual cycle under LEA– but “adaptive” doesn’t mean benign. Long-term hypogonadism can impair quality of life and health in many ways.
It’s not only testosterone that is affected. LEA triggers a cascade of hormonal disturbances: thyroid hormone levels (like T₃) drop, which slows metabolism; cortisol (a stress hormone) tends to rise, which can break down muscle tissue and suppress immunity; and markers of growth factors and anabolic hormones (such as IGF-1 and insulin) decline. Male athletes in a severe energy deficit often have a hormone profile akin to a body under siege: high cortisol paired with low testosterone is a common finding. This combination is problematic – cortisol further encourages muscle breakdown and inhibits muscle protein synthesis, especially when not counterbalanced by testosterone and adequate nutrition. Elevated cortisol also signals that the athlete is in a state of chronic stress, which can contribute to fatigue, poor sleep, and fat redistribution (e.g., more abdominal fat despite overall weight loss). Some athletes describe feeling like their “tank is always empty” or that they’re running on adrenaline – a reflection of these hormonal imbalances.
Metabolic Adaptations and Suppressed Resting Metabolism: The body’s response to prolonged low energy availability includes dialing down the metabolic rate to conserve fuel. Athletes with LEA often exhibit a suppressed resting metabolic rate (RMR) – essentially, their body becomes energy-efficient to a fault, trying to save every calorie for vital functions. One study of professional male cyclists found that 65% of them had a significantly suppressed RMR despite similar daily energy balance on paper; those cyclists spent more time in severe caloric deficits and had larger single-hour energy deficits during the day. The suppressed metabolism was accompanied by higher cortisol and a lower testosterone:cortisol ratio in these athletes. A lower RMR might sound like a minor technical issue, but its effects are noticeable: athletes may feel cold all the time (since the body isn’t wasting heat), experience fatigue or mental fog, and find it hard to lose weight (the body “defends” its energy stores when in starvation mode). Some runners call this the “metabolic slowdown” – despite training hard and eating little, the body stubbornly resists further weight loss and performance stagnates or declines.
Additionally, a chronically suppressed metabolism can cause gastrointestinal disturbances. The review pointed out that endurance athletes in LEA sometimes report digestive problems. This could be due to blood flow being shunted away from the gut (to save energy for muscles and brain) or altered hormone levels affecting gut motility. Athletes may notice constipation, bloating, or simply an uneasy stomach, especially if they’re not fueling enough during long workouts. These GI issues can further reduce appetite, creating a vicious cycle of under-eating.
Bone Health and Injury Risk: Inadequate fueling has well-documented consequences for bone health. When energy and hormone levels are low, the body reduces bone formation – essentially prioritizing short-term survival over building bone density. Male athletes with LEA and low testosterone are prone to decreased bone mineral density (BMD) and more frequent bone injuries. For instance, among a group of elite distance runners studied, those with low testosterone had 4.5 times higher incidence of bone stress injuries (like stress fractures) than those with normal testosterone. This aligns with findings in other sports: male cyclists at risk of LEA showed poorer bone health on scans and blood tests. Even in older research, endurance athletes with “altered reproductive function” and low sex hormones were found to have reduced bone density compared to their peers. Simply put, if you don’t eat enough, you’re not giving your skeleton the materials and hormonal signals it needs to stay strong.
Frequent injuries are one of the hallmark signs of LEA in both men and women. Beyond bone stress fractures, underfueled athletes often have soft tissue injuries (muscle strains, tendinopathies) and longer recovery times for any damage or illness. Poor nutrition means weaker repair processes. Moreover, immune function suffers in an energy-deprived state.
Studies show athletes at low energy availability get sick more often – colds, flus, and other infections – which further disrupts training. The review cited that “disease-related training failure” (basically, missed training due to illness or injury) was three times higher in endurance athletes at risk of LEA, who lost on average 22 days of training per year, compared to about 7 days lost for athletes with adequate energy intake. That’s a huge impact: nearly a month of training wiped out annually, simply from being under-nourished. Over a lifetime, the lost opportunities for development and performance add up.
Other Physiological Effects: Low energy availability can affect virtually every system of the body. Cardiovascular effects may include a lower heart rate and blood pressure (the body in conservation mode) but also the potential for cardiac arrhythmias in extreme cases, due to electrolyte imbalances or loss of cardiac muscle mass – similar to what’s seen in eating disorders. Endocrine effects go beyond sex hormones and thyroid; growth hormone pulsatility may change, insulin sensitivity can be altered, and in females, LEA famously causes menstrual dysfunction. While men don’t have menses, an analogous endocrine disruption is the suppression of the hypothalamic-pituitary-gonadal axis (leading to low LH and testosterone). Renal and hydration aspects might be influenced too – some research suggests the body water and electrolyte regulation can be thrown off by chronic underfueling, partly because of changes in hormone levels like aldosterone and cortisol.
In summary, a male endurance athlete in a state of LEA is likely to experience lowered testosterone, disrupted metabolism, weaker bones, higher injury and illness risk, and a host of other subclinical issues (like nutrient deficiencies, anemia, or chronic inflammation). Individually, any one of these problems can hold back an athlete; combined, they pose a serious threat to both performance and long-term health. Now, let’s consider how LEA can also affect an athlete’s mind and behavior.
Psychological and Emotional Consequences of Low Energy Availability in Male Endurance Runners
LEA doesn’t only strain the body – it also takes a psychological toll. Adequate nutrition is critical for brain function and emotional stability. When the body is underfueled, athletes often experience noticeable changes in mood and cognitive function. Research shows that athletes with low energy availability have a 2.4 times higher likelihood of developing psychological disorders or symptoms compared to those eating enough. Some of the reported psychological consequences include:
Irritability and Mood Swings: Chronically underfed athletes can become unusually irritable, anxious, or moody. If you’ve ever felt “hangry” (hungry-angry), imagine stretching that feeling out over weeks or months of heavy training. Low blood sugar and hormonal fluctuations (like high cortisol and low testosterone) can lead to increased feelings of stress and agitation. Coaches might notice an athlete becoming more short-tempered or emotionally volatile when in an energy deficit. Depression is also a concern – studies have linked LEA/RED-S to higher rates of depressive symptoms. The combination of physical exhaustion and biochemical changes in the brain (due to lack of nutrients) can sap an athlete’s usual enthusiasm and joy for their sport.
Impaired Concentration and Judgment: The brain, like the rest of the body, needs fuel. Low energy availability has been associated with difficulty concentrating, “brain fog,” and impaired judgment. Athletes might find it harder to focus during training sessions, to stay mentally sharp in competitions, or even to perform at work or school. Some runners report feeling “spaced out” or making uncharacteristic mistakes in races (for example, pacing errors or lapses in strategy) when they’ve been dieting too strictly. In essence, LEA can reduce the mental edge that is often crucial in endurance sports where tactics and concentration matter.
Increased Anxiety and Preoccupation with Food/Weight: A cruel irony of low energy availability is that it can heighten anxiety – not just general anxiety, but specifically anxiety about eating and body image. When the body is energy-deprived, the brain may become hyper-fixated on food (an evolutionary response to seek nourishment). Athletes might find themselves constantly thinking about their next meal, craving certain foods, or feeling guilt and anxiety around eating. This can deepen into or exacerbate disordered eating patterns. The review discussed how some psychological factors can be both cause and effect of LEA: an athlete might start under-eating due to body image concerns (cause), which then leads to nutrient deficiencies that aggravate anxiety and obsessive thoughts about weight (effect), trapping them in a vicious cycle. Male athletes, much like females, can develop body dysmorphia or an unhealthy obsession with leanness that perpetuates the cycle of underfueling. What begins as a “strict regimen” to optimize performance can spiral into an unhealthy relationship with food.
Fatigue, Burnout, and Loss of Motivation: It’s no surprise that an undernourished athlete feels tired. But beyond physical fatigue, LEA can cause mental fatigue and burnout. Training that used to be enjoyable may start feeling like a grind. Athletes often describe a loss of motivation, or a sense of “why am I doing this?” when running on empty. Part of this is physiological – low carbohydrate availability can reduce levels of brain neurotransmitters that affect motivation – and part of it is the psychological weight of constantly battling one’s own body. Over time, if not addressed, this can lead athletes to withdraw from training or competition, not because they don’t love the sport, but because they are simply drained. It’s a tragic outcome when a preventable nutrition issue pushes a passionate athlete to the brink of quitting.
Social Withdrawal and Isolation: Eating is a social activity as much as a physical necessity. Athletes struggling with LEA or disordered eating may start to avoid social situations that involve food (like team dinners or celebrations), which can lead to isolation. They might also pull away from friends or teammates because of low mood or because their strict eating/training schedule leaves no room for a social life. This isolation can exacerbate feelings of depression or anxiety, creating a feedback loop.
On a positive note, many of these psychological symptoms are reversible when energy availability is restored. Coaches and athletes have reported remarkable improvements in mood, mental clarity, and overall outlook once the athlete begins fueling adequately again. In some documented cases, athletes didn’t realize how badly LEA was affecting them mentally until they got back to eating enough and suddenly felt like themselves again – happier, sharper, and more emotionally balanced.
It’s worth emphasizing that psychological health is an integral part of athletic performance. An unhappy, anxious, or demotivated runner will not perform to their potential, no matter how “optimally” their training plan is structured. Thus, recognizing the psychological red flags of LEA is just as important as catching the physical ones. If a normally upbeat athlete becomes withdrawn or a disciplined athlete develops anxiety and obsessive behaviors, it’s time to consider energy deficiency as a possible underlying cause.
Impact on Performance and Training
From a coach’s perspective, one of the most frustrating situations is an athlete who is doing all the training but not seeing the results. Low energy availability is often the hidden culprit in these cases. Performance can suffer in multiple ways when an athlete is underfueling:
Decreased Endurance and Strength: It might sound paradoxical, but being too lean or losing weight too quickly can hurt endurance performance. Several studies demonstrate that athletes in an energy deficit see their performance metrics drop. In the review, a study of elite rowers was highlighted: after a four-week intensive training block where the rowers did not eat enough to match the increased training load, they showed worsened recovery and poorer performance on a 5,000m time trial compared to baseline. In trained cyclists, restricting energy during a high-intensity training period led to reductions in both aerobic and anaerobic performance, along with weight loss and a drop in RMR. In other words, those cyclists got lighter, but slower – a net negative for competitive racing. Another finding was that male cyclists who maintained a long-term low-EA state during heavy training had reduced power output and no performance benefit from their weight loss This underscores a critical point: any aerodynamic or efficiency gains from a lower body weight were undermined by the loss of power and endurance resulting from underfueling.
Diminished Training Adaptations: Training is all about stressing the body and then recovering to come back stronger. LEA short-circuits this process. Without adequate energy and nutrients, the body cannot fully adapt to training stimuli. For instance, one study cited in the review looked at elite distance runners training at altitude: those with low energy availability had a blunted increase in hemoglobin mass (a key adaptation to altitude that boosts endurance) compared to those eating enough. Similarly, gains in muscle strength or VO₂max can be compromised if the building blocks (calories, protein, carbohydrates) aren’t sufficient. Essentially, LEA can make an athlete train hard but stay in place – or even regress – because the recovery and adaptation phase is incomplete. Coaches might see an athlete plateau despite increasing mileage or intensity, which is a red flag.
Increased Injury and Illness = Missed Training: As noted earlier, underfueling greatly raises the risk of injuries and sickness. An athlete who is frequently sidelined by tendon pain or respiratory infections simply can’t string together the consistent training needed to improve. The statistic that low-EA athletes lost an average of 22 training days per year to illness/injury vs 7 days for well-fueled athletesshould make any serious runner shudder. That’s three times more downtime. For endurance runners, consistency is king – months and years of uninterrupted training build success. If LEA is causing you to break down every few weeks, it’s like trying to build a pyramid while constantly removing bricks from the base. Performance will inevitably suffer.
Impaired Coordination and Technique: An often overlooked aspect of performance is neuromuscular function – things like coordination, reaction time, and technique. The review mentions impaired coordination as one consequence of RED-S. Low energy and fluctuating blood sugar can affect nerve and muscle firing patterns, possibly making an athlete more clumsy or less precise in their movements. In running, this might manifest as a deterioration in form at the end of a long run or workout (beyond what fatigue alone would cause), or even a slight delay in reaction that could be dangerous in trail running or during a race surge. Over time, poor nutrition might also reduce the athlete’s ability to do high-quality speed or technical work – they just won’t have the explosiveness or focus for it.
Stagnation Despite “Optimal” Training: One of the insidious things about LEA is that an athlete can be hitting all their planned splits and volumes, yet remain stuck in performance. A coach might scratch their head and say, “Everything looks right, so why aren’t you improving?” The answer might lie off the track and in the kitchen. If the body perceives a chronic energy shortage, it may essentially put the brakes on improvement as a self-protection mechanism. Runners might find they cannot increase their lactate threshold or they keep hitting the same race times season after season. These could be signs that the issue isn’t in the training plan but in the nutritional plan.
It’s not all doom and gloom, however. The flip side is that addressing LEA can lead to significant performance breakthroughs. Athletes who start fueling properly often experience “night and day” differences: more energy in workouts, the ability to hit higher intensities, better recovery (so they can train more consistently), and ultimately improved race times. Many elite coaches now emphasize fueling as the “next frontier” of performance gains, especially in sports like distance running where training approaches are already highly refined. The bottom line is that food is fuel, and without enough fuel, even the best-engineered training program will underdeliver.
Recognizing the Signs and Taking Action
Given the serious consequences of low energy availability, it’s crucial for athletes and coaches to recognize the warning signs. Sometimes, the indicators are subtle and can masquerade as other issues, but a pattern or cluster of these signs should raise concern about LEA in a male endurance athlete:
Persistent Fatigue: This is more than just the normal tiredness from training. We’re talking about a deep, lingering fatigue that doesn’t improve with rest days or down weeks. The athlete may feel drained all day, not just during runs.
Plateau or Decline in Performance: If race times are stagnating or getting slower despite proper training, or if the athlete feels like they’ve “lost their mojo,” it could be LEA. A sudden drop in performance, in particular, should prompt a look at nutrition.
Frequent Injuries and Illnesses: Multiple stress fractures or bone injuries, recurring colds, flu, or other infections, constant niggles that don’t heal – these are big red flags. For example, an athlete who suffers two stress fractures in a short time frame should be evaluated for underlying energy deficiency and bone density issues.
Changes in Mood or Behavior: Increased irritability, depression, or anxiety, as discussed, can be a sign. Also, if an athlete becomes more withdrawn or obsessed with food/weight, take note. Teammates and coaches might observe that the athlete “just isn’t themselves lately.”
Loss of Libido or Sexual Dysfunction: Though often a private matter, male athletes (or their partners) might notice a reduced sex drive or other sexual issues. In a young, healthy male, that can be a canary in the coal mine for low testosterone and energy availability.
Chronically feeling cold or having other physiological signs: For instance, some athletes experience hair thinning or loss of libido when energy availability is low (a result of hormonal shifts). Difficulty staying warm even in moderate conditions, or often having cold hands and feet, can indicate a slowed metabolism.
Digestive Problems: Ongoing constipation, bloating, or stomach discomfort that isn’t explained by another medical condition might be related to underfueling. Remember, the body in LEA is reducing “unnecessary” functions, and unfortunately digestive health can take a hit.
Sudden Weight Changes: Unintended weight loss (especially if the athlete wasn’t trying to lose weight) is an obvious sign of energy deficit. However, even weight stability doesn’t rule out LEA – as mentioned, one can be weight-stable and still underfueling. On the flip side, some athletes actually gain weight when severely underfueling, due to metabolic adaptation. The key is any unexplained weight change coupled with performance or health issues should prompt a closer look.
If multiple of these signs are present, it’s time to take action in a supportive, non-judgmental way. Here’s what athletes and coaches can do:
Open a Dialogue and Seek Professional Help: It’s important to remove any stigma around these issues. A coach or run buddy might gently inquire if the athlete is eating enough or suggest meeting with a sports nutritionist or dietitian. Sometimes an athlete might not realize they are underfueling until a professional analyzes their intake and energy expenditure. A licensed dietitian familiar with sports can estimate how many calories the athlete needs and identify gaps in the diet (for instance, not eating enough carbohydrates for the training load). They can help set up a nutrition plan that ensures adequate energy availability throughout the day – including around workouts and for recovery. Education is key: many athletes simply haven’t been taught how much fuel endurance training truly requires.
Medical Evaluation: Given the hormonal components of LEA, consulting a sports medicine physician or endocrinologist can be very useful. A doctor can order blood tests to check hormone levels (testosterone, thyroid function, cortisol, etc.), assess vitamin/mineral status (like iron or vitamin D, which are critical for performance and bone health), and evaluate bone density if needed. The review suggests regular check-ups of blood markers and body composition for at-risk athletes. For instance, an unexpectedly low testosterone reading in a young male athlete can confirm the presence of hypogonadism related to energy deficiency. This medical feedback often provides a wake-up call and can be tracked over time as the athlete increases their energy intake (testosterone and other hormones will often rebound with proper fueling, though it can take months). In some cases, a DXA scan or other bone density test might be warranted if stress fractures have been an issue – low BMD would point strongly to chronic LEA and prompt aggressive nutritional intervention.
Increase Energy Intake (Eat More, and More Often): This is the most direct solution – the athlete needs to get more calories in, ideally in a balanced way with plenty of carbohydrates, protein, and healthy fats. Sometimes just adding a couple of nutrient-dense snacks during the day (like a smoothie, yogurt with granola, or peanut butter sandwiches) can start to turn things around. Athletes should be encouraged to fuel around workouts, not just later. Consuming carbohydrate during long training sessions (e.g., sports drinks, gels) not only improves performance but also helps reduce the dip into LEA by providing energy when the body needs it most. Having a good recovery meal or shake immediately after hard workouts is crucial to restock energy and kickstart muscle repair. Essentially, aligning nutrition timing with training can prevent the body from ever being in too severe a deficit. Moreover, if weight loss is truly needed for performance (which should be carefully considered), it must be done gradually and in the off-season under professional guidance, not during peak training when fueling is paramount.
Monitor and Adjust Training Load: While nutrition is being corrected, it may also be wise to dial back training intensity or volume temporarily. This gives the body a chance to heal and rebalance. It can be psychologically tough for athletes to train less, but a short-term step back can lead to long-term gains once they return with better energy availability. Coaches can reassure athletes that reducing training to focus on health is an investment in future performance. Pairing this with improved nutrition creates the best environment for a strong comeback.
Education on Body Image and Performance: Athletes often need support to reframe their thinking: leanness at all costs is not the ticket to success. The conversation should shift to “energy availability” and performance rather than weight. Some athletes fear that eating more or gaining a little weight will slow them down, but evidence and real-world examples show that a well-fueled runner often runs faster and feels better. It can help to point out elite male marathoners or triathletes who are not stick-thin but are dominating races, thanks in part to having energy to train and recover effectively. Emphasizing strength, resilience, and consistency over a certain look can gradually improve the athlete’s relationship with food and their body. Remember, there is a fine line between the positive adaptation of carrying a healthy racing weight and the negative consequences of crossing into energy deficiency. Finding that balance is key.
Regular Screening and Awareness: Going forward, it’s wise for endurance athletes to keep tabs on their energy availability. This doesn’t necessarily mean counting every calorie, but rather being mindful of fueling sufficiently for the work done. Some athletes do well with keeping a training log that also notes meals or energy levels, which can help catch patterns (e.g., “whenever mileage goes above X per week, I start skimping on dinner and feel lousy”). Sport science is also working on practical screening tools for LEA risk – for example, questionnaires that flag athletes who might be at riskncbi.nlm.nih.gov. Until those are refined, the combination of self-awareness, coach observation, and periodic check-ins with health professionals is the best strategy. Early intervention is much easier than trying to fix broken bone health or long-term hormone disruptions, so maintaining awareness can prevent small energy deficits from becoming big problems.
Final Thoughts
“Running on empty” might sound poetic, but in reality it is a recipe for broken bodies and unfulfilled potential. Low energy availability is a silent threat that can undercut an endurance athlete’s hard work. The recent review of male endurance athletes confirms that men face physiological and psychological consequences strikingly similar to those long recognized in female athletes – from hormonal havoc and brittle bones to mood slumps and stalled performance. The good news is that knowledge is power. By understanding LEA and recognizing its signs, athletes and coaches can take proactive steps to ensure athletes are properly fueled. In a culture that often glorifies pushing the limits, it’s important to remember that food is not the enemy – it is fuel and medicine. An athlete who fuels smartly and abundantly will likely find themselves training harder, recovering faster, feeling happier, and ultimately racing faster.
Male endurance runners should know that taking care of their energy availability is not a sign of weakness; on the contrary, it’s a mark of a wise and disciplined athlete. It shows a commitment to long-term improvement and health. If you’re a runner or coach, consider this an invitation to foster a training environment where eating enough is as much a part of the plan as the miles and intervals. As the science of RED-S and LEA continues to evolve, we are learning that performance and health truly go hand in hand. By nourishing our bodies, we’re also nurturing our ambition and passion for the sport.
In the end, the goal is a thriving athlete who can handle challenging training, bounce back strong, and enjoy a long, successful running career. That goal is infinitely more achievable when we respect the body’s need for energy. So the next time you lace up for a long run, remember: the fuel in your tank determines how far and fast you can go. Let’s make sure we aren’t running on empty, but rather running on a full tank towards our personal bests – with strength, resilience, and joy in the journey.
Sources
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Areta JL, Taylor HL, Koehler K. Low energy availability: history, definition and evidence of its endocrine, metabolic and physiological effects in prospective studies in females and males. Eur J Appl Physiol. 2021;121(1):1-21. doi:10.1007/s00421-020-04516-0
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
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