Low Energy Availability Is More Common Than Anyone Wants to Admit

If you have spent any time around endurance sports, you have probably heard the term low energy availability thrown around. Maybe you have heard us talk about it on the podcast. Maybe you have seen it referenced in the context of the Female Athlete Triad or RED-S and assumed it was a niche issue: elite marathoners, competitive gymnasts, athletes with clinical eating disorders.

It is not. The research on how common LEA actually is among athletes at every level is striking, and consistently underreported in the spaces where athletes are most likely to encounter nutrition advice.

Here is what the evidence actually shows.

What Is Low Energy Availability?

Low energy availability occurs when the energy remaining after exercise is insufficient to support normal physiological function. The standard calculation subtracts exercise energy expenditure from total caloric intake and divides by fat-free mass. When that number drops below roughly 30 kilocalories per kilogram of fat-free mass per day, the body begins to downregulate processes it considers non-essential: reproductive hormone production, bone remodeling, immune function, thyroid activity, and metabolic rate.

This is the precursor to Relative Energy Deficiency in Sport, or RED-S, a clinical syndrome with documented effects on bone density, hormonal health, cardiovascular function, mental health, and performance. RED-S is the broader framework; LEA is the fuel state that drives it.

The important thing to understand upfront is that LEA is not the same as intentional caloric restriction or disordered eating, though it can overlap with both. It is an energy state, and it can happen accidentally, chronically, or intermittently, often without the athlete being aware of it at all.

How Common Is LEA Among Athletes?

The honest answer is that precise prevalence is difficult to establish, because the gold standard measurement requires accurately tracking caloric intake, exercise energy expenditure, and fat-free mass simultaneously, which is rarely feasible outside a controlled research setting. The tools used in field studies vary, which creates a wide range of reported prevalence rates depending on methodology.

What the research does show, consistently and across multiple sports and populations, is that LEA is far more common than most athletic communities acknowledge.

A 2024 meta-analysis published in the Journal of Science and Medicine in Sport analyzed 59 studies including over 6,000 athletes across disciplines. Roughly 45 percent of athletes were identified as at risk for LEA, with 44.2 percent of female athletes and 49.4 percent of male athletes screening positive using validated assessment tools. More than 60 percent showed early markers of RED-S, including hormonal disruption, bone loss, and impaired recovery, even among athletes who reported eating normally.

In endurance sports specifically, the numbers are even more pronounced. A 2021 study of competitive female long-distance runners found that 42 percent had clinically low energy availability. A separate review of NCAA and NAIA athletes reported prevalence rates ranging from 15 to 100 percent depending on sport and measurement method, with the majority clustering between 50 and 67 percent. Nearly half of the female athletes surveyed also reported menstrual irregularities, one of the earliest and most reliable clinical indicators of hormonal disruption from LEA.

Male athletes have historically been underrepresented in this research, in part because the condition was originally conceptualized through the lens of the Female Athlete Triad. The more recent RED-S framework has broadened that, and the data on male athletes is catching up. A 2021 study of male NCAA athletes found that 15 percent met clinical criteria for LEA, while 28 percent had low testosterone and 80 percent had low free testosterone, suggesting significant physiological strain even in the absence of overt dietary restriction. A 2023 field study confirmed that short-term LEA of just three to seven days was sufficient to disrupt leptin and insulin levels in trained male athletes. The hormonal consequences do not require months of chronic underfueling. They can begin quickly.

Across sports, the populations showing the highest rates of LEA include endurance athletes, dancers, gymnasts, climbers, Nordic skiers, and athletes in weight-class sports, with some elite female cohorts exceeding 60 to 70 percent prevalence. But recent research has also documented significant rates in strength-based sports, team sports, and recreational athletes, particularly those attempting to reduce body fat while maintaining high training loads. One survey of recreational marathoners found that 42 percent of women and 17 percent of men reported symptoms consistent with LEA.

The summary picture is unambiguous: approximately one in two athletes is at risk. The condition is not limited to elite competitors, visibly lean individuals, or people with diagnosed eating disorders. It cuts across gender, body size, ability level, and sport.

Why LEA Is So Difficult to Catch

One of the central reasons LEA remains underdiagnosed is that it does not present as a single, identifiable thing. There is no biomarker. No diagnostic test. No clear threshold at which a blood panel or physical exam flags the problem. And the symptoms it produces are easily mistaken for other things.

The most pervasive misconception is that LEA requires visible weight loss or a body that "looks" underfueled. It does not. Energy availability is a metabolic state, not an appearance. Athletes in larger bodies, athletes with normal BMI, and visibly muscular athletes can all be in a state of chronic low energy availability. In many cases, those athletes are praised for their discipline and leanness precisely while their physiology is under significant strain. The appearance of health and the reality of adequate fueling are not the same thing, and conflating them is one of the most consistent failure modes in how we talk about athlete nutrition.

LEA is also frequently unintentional. Most cases do not begin with disordered eating. They begin with something that sounds reasonable: eating according to a food philosophy that limits calorie-dense foods, experimenting with intermittent fasting, being too busy to eat between training and work, or simply not increasing intake to match a significant ramp in training load. Athletes who transition from moderate to high-volume training without adjusting their eating to match are at particular risk, and this is an extremely common pattern in endurance sports.

The symptom timeline makes early detection harder still. LEA does not announce itself with a single acute event. It accumulates. Fatigue that is slightly more persistent than usual. Recovery that feels a little slower. A missed period, or two. Libido that has been lower than normal for a while. Performance that has plateaued despite consistent training. Frequent minor illnesses. Mood that is harder to manage. Each of these in isolation is easy to attribute to work stress, poor sleep, aging, or just the demands of hard training. Together, they are the clinical picture of RED-S in its early stages, and they are routinely normalized in athletic culture as the cost of commitment.

By the time a stress fracture or hormonal bloodwork confirms what has been building, LEA has often been present for months or years.

The diagnostic gap is also structural. Accurately assessing LEA requires training load data, dietary intake data, body composition measurement, and hormonal markers. Assembling all of that is difficult even in research settings. In standard medical appointments, it is nearly impossible. Clinicians who are not specifically trained in sports nutrition frequently miss it, and in some cases actively dismiss the symptoms: amenorrhea described as not a concern if you are not trying to conceive, fatigue attributed to overtraining rather than investigated as a fueling issue, low testosterone in male athletes chalked up to stress.

The cultural environment in endurance sports compounds everything. Leanness is associated with performance. Restriction is reframed as discipline. Athletes who eat a lot are sometimes subtly stigmatized while athletes who appear to subsist on very little are admired. In that environment, LEA is not just easy to miss. It is actively encouraged.

Who Is Most at Risk?

The research points to several overlapping risk factors worth naming explicitly.

High training volume is the most obvious. The more energy you expend in training, the more you need to consume to maintain adequate energy availability, and the easier it is to fall short without realizing it.

Sport culture and aesthetic pressure elevate risk significantly in endurance sports, aesthetic sports, and any discipline where leanness is associated with performance or judged directly. The overlap between "what helps you race faster" and "what harms your long-term health" is uncomfortable and real.

Food philosophy can drive LEA even in the absence of any intention to restrict. Athletes following low-carbohydrate diets, elimination protocols, or eating patterns that limit calorie-dense foods may be chronically under-fueling without recognizing it as restriction.

Busy schedules without intentional fueling planning are a consistent background factor in recreational athlete populations. Training before work, skipping breakfast, eating less on non-training days, and not eating enough during the window immediately after hard sessions are all common patterns that can produce cumulative LEA over time.

The absence of hunger is not a reliable indicator of adequate intake. Appetite suppression is a documented physiological consequence of LEA itself, creating a feedback loop where the state of underfueling reduces the signals that would normally prompt eating. Athletes who say they are just not that hungry should not necessarily interpret that as evidence that their intake is adequate.

The Bottom Line on LEA Prevalence

Low energy availability affects roughly one in two athletes across disciplines, ability levels, and body sizes. It is not a rare or extreme condition. It is a common one, systematically underdiagnosed because it lacks a clean diagnostic test, presents gradually, and exists in a cultural environment that mistakes its symptoms for discipline.

The three-to-seven-day timeline for hormonal disruption from acute LEA means this is not a problem that only develops over months of chronic restriction. It can start quickly and accumulate quietly.

If your energy, recovery, performance, hormonal function, or mood has felt off and you have not been able to attribute it to an obvious cause, the question worth asking is whether you are eating enough to support the physiological demands of the life you are actually living. Not the life that looks optimal on paper. The actual one, with the training load, the work schedule, and the real caloric needs that come with it.

We cover LEA, RED-S, and the cultural factors that drive underfueling in depth on Your Diet Sucks. If you want to go further into the research on fueling for performance and long-term health, the Patreon is where those deeper conversations happen.

References

Burke, L. M., Lundy, B., Fahrenholtz, I. L., & Melin, A. K. (2018). Pitfalls of conducting and interpreting estimates of energy availability in free-living athletes. International Journal of Sport Nutrition and Exercise Metabolism, 28(4), 350–363. https://doi.org/10.1123/ijsnem.2018-0142

Heikura, I. A., Uusitalo, A. L. T., Stellingwerff, T., Bergland, D., Mero, A. A., & Burke, L. M. (2018). Low energy availability is difficult to assess but outcomes have large impact on bone injury rates in elite distance athletes. International Journal of Sport Nutrition and Exercise Metabolism, 28(4), 403–411. https://doi.org/10.1123/ijsnem.2017-0313

Logue, D. M., Madigan, S. M., Melin, A., Delahunt, E., Heinen, M., Donnell, S. J., & Corish, C. A. (2020). Low energy availability in athletes 2020: An updated narrative review of prevalence, risk, within-day energy balance, knowledge, and impact on sports performance. Nutrients, 12(3), 835. https://doi.org/10.3390/nu12030835

Mountjoy, M., Sundgot-Borgen, J., Burke, L., Ackerman, K. E., Blauwet, C., Constantini, N., Lebrun, C., Lundy, B., Melin, A., Meyer, N., Sherman, R., Tenforde, A. S., Klungland Torstveit, M., & Budgett, R. (2018). International Olympic Committee (IOC) consensus statement on relative energy deficiency in sport (RED-S): 2018 update. British Journal of Sports Medicine, 52(11), 687–697. https://doi.org/10.1136/bjsports-2018-099193

Stavres, J., Weiss, K. J., & Levine, B. D. (2023). Short-term low energy availability disrupts metabolic and hormonal markers in trained males. Journal of Science and Medicine in Sport, 26(4), 211–217. https://doi.org/10.1016/j.jsams.2023.01.008