Prevalence Survey and Health Impacts of Low Energy Availability (LEA) Among Taiwanese Endurance Athletes

Based on peer-reviewed research from international sports science journals, this article provides an in-depth analysis of the impact of “Low Energy Availability” on athletic performance, combined with Taiwan-specific riding and race scenarios, offering actionable training nutrition advice.

Low Energy Availability (LEA) is the most serious yet most overlooked issue in sports nutrition, triggering RED-S (Relative Energy Deficiency in Sport) and affecting bone health, endocrine function, immunity, and performance.

In Taiwan’s endurance sports community—whether it’s the climbing enthusiasts tackling the West Route to Wuling, the long-distance riders heading East through the Huatung Valley, or participants in the Sun Moon Lake loop, Taroko Marathon, and 226km Ironman triathlons—the topic of “Low Energy Availability” matters because it directly determines whether you can maintain your pace in the latter stages of an event, avoid cramping and hitting the wall, and recover effectively between consecutive training days. Many amateur athletes pour all their effort into power training and equipment upgrades while overlooking nutrition—this “free margin for improvement.” In fact, when training volume and equipment are comparable, the quality of nutritional strategy is often the decisive variable separating finishers from DNFs, and personal bests from blow-ups. This article will guide you through the complete context—from cellular molecular mechanisms and randomized controlled trial evidence to dose-response curves and practical application—debunking long-circulated myths and putting your fueling strategy on a truly scientific foundation.

Academic Research Review

Regarding the scientific exploration of “Low Energy Availability,” top international journals have accumulated rich and rigorous evidence. Below are several representative studies selected for their value in methodological design, sample populations, and strength of conclusions, which together form our current understanding of this topic:

1. Mountjoy M et al. (2014/2018, BJSM) proposed and updated the RED-S consensus statement.

2. Loucks AB (2003, J Sports Sci) established the 30 kcal/kg FFM energy availability threshold.

3. Melin A et al. (2015, Scand J Med Sci Sports) developed the LEAF-Q screening tool.

4. Logue D et al. (2018, Sports Medicine) reviewed the negative effects of LEA on performance.

Taken together, these studies show that the scientific picture of “Low Energy Availability” is not a single fixed conclusion, but rather one that is continuously refined and deepened as research methods advance. Early studies mostly employed laboratory-controlled time trials or exhaustion tests; subsequent research gradually introduced stable isotope tracing, muscle biopsies, functional magnetic resonance imaging (fMRI), and molecular biomarkers, allowing us to move from “phenomenon observation” to “mechanistic explanation.” Notably, most high-quality studies use a randomized crossover design, where each subject serves as both experimental and control, greatly reducing noise from individual differences. However, extrapolation of research conclusions still requires caution: the responses of well-trained laboratory subjects may not fully apply to the general amateur athlete; the effects of a single acute intervention may not equal long-term chronic adaptation. When reading the “effect sizes” and “statistical significance” of these studies, one must also distinguish between ‘statistically significant’ and ‘practically meaningful’—a 1% improvement may determine medal placement in elite competition, but its significance for a recreational rider is relatively limited.

Core Mechanisms

Energy Availability = (Energy Intake − Exercise Expenditure) / Fat-Free Mass. When below 30 kcal/kg FFM, the body downregulates non-essential functions: suppressing the gonadal axis (amenorrhea), reducing bone density, and impairing thyroid and immune function. Long-term LEA leads to stress fractures, performance plateaus, and health deterioration, affecting both men and women.

To truly understand how “Low Energy Availability” affects athletic performance, one must return to physiology at the cellular and systemic levels. Athletic performance is the result of multi-system coordination: the cardiovascular system delivers oxygen and fuel, muscle cells handle energy conversion and mechanical contraction, the central nervous system regulates motor unit recruitment and fatigue perception, while the gut and liver form the hub of nutrient absorption and metabolism. These mechanisms translate into measurable performance differences precisely because they act on one (or multiple) critical links in this chain. The table below summarizes the key points of action at different physiological levels for this topic, helping you build a complete mechanistic picture:

| Level of Action | Key Mechanisms | Significance for Athletic Performance |

|—|—|—|

| Cellular/Molecular | Affects mitochondrial efficiency, enzyme activity, and signal transduction | Determines the efficiency of energy conversion and adaptive direction |

| Muscle Tissue | Regulates substrate utilization, buffering capacity, and contractile function | Affects sustainable power output and fatigue onset |

| Systemic Integration | Alters blood flow distribution, thermoregulation, and hormonal environment | Determines stability and safety during prolonged exercise |

| Central Nervous System | Regulates fatigue perception, drive, and motor unit recruitment | Affects “how tired it feels” and the ability to persevere |

Particular emphasis should be placed on the two dimensions of “dose-response” and “temporal dynamics.” The same nutritional intervention, at different doses and different timing, can produce vastly different or even opposite effects—this is precisely why much of the common advice circulating is one-sided. Only by understanding the mechanisms can we judge ‘when to use it, how much to use, and when to time it,’ rather than blindly following trends.

Furthermore, the limiting factors of athletic performance shift dynamically with exercise intensity and duration: in short, high-intensity efforts, limitations often stem from the accumulation of phosphagen system depletion and glycolytic byproducts; in multi-hour endurance events, limitations shift toward the combined effects of glycogen depletion, rising core temperature, fluid and electrolyte imbalance, and central fatigue. “Low Energy Availability” deserves in-depth discussion precisely because it can specifically target certain of these limiting factors. This also reminds us that no nutritional strategy can be evaluated in isolation from the “exercise context”—a fueling rhythm suitable for a 40-minute criterium may not apply to a 6-hour climbing epic, and vice versa. The more thoroughly you understand the mechanisms, the more flexibly you can adjust across different event formats, rather than rigidly adhering to a fixed formula. This ability to “adapt to context” is precisely the dividing line between amateur athletes and those who truly understand sports science.

Dose-Response Relationship

In sports nutrition, “the dose determines both the toxicity and the benefit.” Too low a dose fails to reach the physiological threshold and is futile; too high a dose may trigger side effects, gastrointestinal distress, and even interfere with training adaptations. The table below outlines the dose-response relationship for “Low Energy Availability” and serves as the most important quantitative reference when developing a personal fueling plan:

| Dose / Condition | Effect Description |

|—|—|

| > 45 kcal/kg FFM | Optimal energy availability |

| 30–45 | Critical zone |

| < 30 kcal/kg FFM | LEA risk, downregulation initiated |

| Chronic LEA | Fractures/amenorrhea/immunosuppression |

From the table above, it is clear that benefits often follow an “inverted U-shaped” or “threshold-plateau” curve: effects increase with dose until the effective threshold is reached, but beyond a certain plateau point, there is not only no additional benefit, but marginal costs (side effects, gastrointestinal burden, financial expense) rise sharply. This means that “finding your own optimal dose” is far more important than “eating as much as possible.” It is recommended to progressively test different doses during training (not on race day), recording subjective feelings, gastrointestinal responses, and power data to build your own dose profile. Remember: the laboratory average is a starting point, not an endpoint; each person’s body weight, metabolic rate, gut tolerance, and genetic background will cause individualized shifts in the optimal dose.

Differences Across Populations

The benefits of “Low Energy Availability” are not equal for everyone. Age, sex, training status, body composition, and genetic background all significantly modulate individual response magnitude. Ignoring these differences and applying a one-size-fits-all recommendation is one of the most common errors in sports nutrition.

| Population Aspect | Response Characteristics | Practical Recommendations |

|—|—|—|

| Beginners vs. Advanced | Advanced athletes have more mature physiological adaptations; responses are often more stable but with smaller marginal gains | Beginners should start conservatively with low doses, building tolerance first |

| Male vs. Female | Differences in body weight, hormonal cycles, and sweat composition affect dosing and requirements | Females should individualize by body weight and pay attention to iron and energy availability |

| Younger vs. Older | Older individuals often have reduced absorption efficiency and anabolic resistance | Older individuals may require higher doses or better timing |

| Body Size Differences | Body weight directly affects absolute amounts calculated per mg/kg or g/kg | Always convert to a dose corresponding to individual body weight; avoid copying general rules |

When interpreting “individual differences,” one must also be wary of a common statistical trap: studies mostly report “group mean responses,” but beneath the average often lies enormous individual variability. In the same intervention, there may be strong responders, non-responders, and even negative responders. This is why even when a study shows ‘average effectiveness,’ you still need to confirm through your own testing which category you fall into. The recommended approach is to conduct personalized A/B testing: in two training sessions with as similar conditions as possible, with and without the strategy respectively, compare power, heart rate, and subjective feelings, repeating several times before drawing conclusions. This empirical spirit of “using yourself as the sample” is the essential path from group science to personal prescription.

Taking Taiwan’s common amateur endurance population as an example, many are middle-aged riders over 35 who train around work commitments. This group simultaneously faces declining recovery speed, insufficient sleep, and time pressure, so the “return on investment” of nutritional strategies is often higher than for younger elites—meaning that correct nutritional intervention can yield relatively greater room for improvement. Female athletes need to pay particular attention to the effects of the menstrual cycle on metabolism and requirements, as well as whether energy availability is sufficient, avoiding the trap of falling into Low Energy Availability (LEA) while pursuing weight loss. After understanding population differences, you will realize: truly professional nutritional advice is always an individualized prescription that “varies by person,” not a one-size-fits-all slogan.

Practical Training Application

Theory must ultimately translate to training plans and race courses. Below is a practical framework for converting “Low Energy Availability” into concrete training and competition operations:

• Pre-Race Testing Principle: All nutritional strategies must be rehearsed in training first; “never try anything new on race day” is an iron rule. Gut tolerance to new fueling products takes time to build.

• Periodization Mindset: Align nutritional strategies with the training cycle—the base phase can emphasize adaptation-oriented strategies, while the pre-season shifts to performance-oriented fueling optimization.

• Progressive Introduction: Start with low doses and low frequency, adjust gradually based on body responses, and build a personalized dose and timing profile.

• Data Tracking: Combine power meter data, heart rate, subjective fatigue (RPE), and gastrointestinal comfort records to objectively evaluate whether an intervention is truly effective.

• Holistic Context: Nutrition is one component of training, sleep, recovery, and psychology; no single supplement can compensate for sleep deprivation or flawed training design.

Using a weekly training schedule as an example, it is recommended to rehearse different fueling scenarios during key mid-week high-intensity sessions (such as threshold intervals or repeated climbs) and weekend long rides: high-intensity days focus on rapid energy supply and central activation, while long-distance days focus on sustained fueling, gut tolerance, and recovery. Through repeated rehearsal, your body can execute the optimal fueling rhythm “automatically” on race day, leaving mental resources for pacing and tactical decisions. Remember, the goal of a nutritional strategy is not theoretical perfection, but stable reliability under the fatigue, heat, and pressure of a real race course.

The most common mistake many people make when executing a nutrition plan is “being serious only on race day and eating carelessly during regular training.” This is precisely putting the cart before the horse: regular training is the ideal laboratory for building gut tolerance, testing doses, and cultivating fueling rhythm. If you want to execute an 80g carbohydrate per hour fueling plan on race day, you must rehearse it repeatedly in training until your body becomes accustomed; if you want to rely on a particular supplement, you must confirm in training that it is genuinely effective for you and free of side effects. It is recommended to integrate a nutrition log with your training log, recording fueling content, intake timing, gastrointestinal responses, and performance data for each key session. After weeks to months of accumulation, the value of this personalized database will far exceed any generic nutrition guide. Additionally, do not overlook the often-underestimated “post-training recovery fueling” component—the quality of recovery between consecutive training days often determines whether you can steadily accumulate training volume without injury, and training volume is the most fundamental engine of long-term progress. Treat nutrition as an integral part of training rather than a last-minute accessory before races, and your progress curve will be noticeably different.

Taiwan-Specific Application

Taiwan’s unique climate, terrain, and race culture add localized considerations to the application of “Low Energy Availability.” Taiwan’s summer is hot and humid, with perceived temperatures often exceeding 35°C, and sweat rates and fluid/electrolyte losses far exceeding the research contexts of temperate countries—meaning that hydration and fueling recommendations from foreign literature often need to be “revised upward.” In events like the West Route to Wuling, which climbs from sea level to 3,275 meters, the appetite suppression at altitude, low temperatures, and prolonged exercise pose a severe test for energy planning.

Regarding local fueling options, Taiwan’s abundant bananas, sweet potatoes, pineapples, sports drinks, and convenience store ready-to-eat foods can all be incorporated into fueling strategies; the extremely high density of convenience stores also makes mid-ride refueling on long distances relatively easy. It is recommended that Taiwanese riders planning classic routes such as Sun Moon Lake, Wuling, Beiyi, Buyanting, and the East Route scout fueling points along the way in advance, and strengthen sodium and fluid supplementation given Taiwan’s humid and hot environment. Athletes in the Taroko Marathon, Taipei Marathon, and various triathlon events across the island should likewise incorporate these local climatic factors into their individualized nutrition plans to perform at their best under subtropical conditions.

Common Myth Debunking

Myth: The myth is that ‘being lighter makes you faster.’ In reality, chronic energy deficiency triggers RED-S, which instead leads to decreased performance, injuries, and health crises.

Such myths spread widely often because they “sound reasonable,” are easily passed by word of mouth, or are amplified by marketing rhetoric. Yet the value of science lies in testing intuition with rigorous evidence: many seemingly obvious notions fail to hold up under scrutiny in randomized controlled trials. The field of sports nutrition is especially rife with oversimplified “panacea” style marketing that compresses complex dosing, timing, and individual differences into a single slogan. The next time you hear a categorical nutritional claim, it’s worth asking: “What is the level of evidence for this claim? Who is the target population? Are the dose and timing clearly specified?” Cultivating this evidence-based critical thinking is more valuable than memorizing any single conclusion, and is a key step for amateur athletes toward scientific training.

Conclusion

“Low Energy Availability” is a topic in sports nutrition with both theoretical depth and practical value. From the academic evidence reviewed in this article, its benefits are real, but it is by no means an unconditional panacea—the key lies in correct dosing, appropriate timing, individualized adjustment, and synergy with overall training, recovery, and sleep. For Taiwan’s endurance sports enthusiasts, while mastering the scientific principles, it is equally important to combine local climate, terrain, and race characteristics to translate general rules into a personalized prescription that suits you. May every rider sweating on Wuling, in the valley, or on the round-island route break through their limits through science-based nutritional strategies and enjoy the pure joy that sport brings. Before you next hit the race course, don’t forget—your fuel bottle holds not just water and sugar, but an entire validated body of sports science.

Related Reading

• The Impact of Carbohydrate Availability on Training Adaptations: The Mitochondrial Benefits of Low-Carb Training
• Daily Energy Availability Management for Female Endurance Athletes: Turning “Eating Enough” into Executable Training Discipline
• A Survey of the Dietary Status of Taiwanese Professional Cyclists: Energy Intake and Macronutrient Analysis
• Relative Energy Deficiency in Sport (RED-S): The Most Dangerous Dietary Trap for Endurance Athletes