A MODERN SPORTS DIETITIANS’ INSIGHT

– Written by Nelda Nader, Shaikha Mahmoud Abdulla, and Amna Hamad AlSulaiti, Qatar

INTRODUCTION

Bone Stress Injury (BSI) refers to a spectrum of stress-related bone pathologies ranging from early stress reactions, characterized by microdamage and inflammation, to overt stress fractures, often caused by repetitive mechanical loading that exceeds the bone’s capacity to adapt¹. BSIs pose a significant challenge for athletes, often resulting in prolonged time away from training and competition, which can adversely affect performance and, in some cases, threaten long-term athletic careers¹.

Recent research highlights the critical role of nutritional and hormonal factors in maintaining bone integrity and influencing injury risk. Factors such as Low Energy Availability (LEA), vitamin D deficiency, female menstrual dysfunction, poor bone health, and hormonal imbalances, impair bone remodeling and increase susceptibility to BSIs²  (refer to Figure 1).

Epidemiological data further illustrates the burden of BSI in elite sport. A retrospective cohort study of high-performance athletes documented that bone stress injuries comprised 0.15% of all recorded injuries over a three-year period, with female athletes experiencing nearly twice the incidence of males; moreover, injury patterns were found to be sport-specific³. Track and field athletics consistently demonstrates some of the highest annual injury rates among sports, with bone stress injuries accounting for up to 20% of all musculoskeletal injuries in this population⁴.

Bone mineral density (BMD) naturally declines with age, but suboptimal BMD in athletes can reflect underlying nutritional and hormonal disturbances, which, when combined with repetitive mechanical loading, elevate BSI risk. Studies have shown that lower BMD is associated with a higher likelihood of developing bone stress injuries, emphasizing that both bone quality and mechanical stress contribute significantly to BSI occurrence⁵.

Due to the multifactorial nature of BSI, a multidisciplinary approach is essential following diagnosis. Effective management not only involves thorough evaluation of clinical symptoms, training history, hormonal status and rehabilitation, but should include a nutritional assessment and planning to optimize recovery and minimize recurrence^1,2. 

BSI: A RED FLAG FOR RELATIVE ENERGY DEFICIENCY IN SPORT (RED-S) AND LOW ENERGY AVAILABILITY (LEA)

One critical aspect of nutritional assessment is understanding the role of Energy Availability (EA) and its deficiency, which is central to the development of RED-S and LEA. RED-S is defined as “A syndrome of impaired physiological and/or psychological functioning experienced by female and male athletes that is caused by exposure to problematic (prolonged and/or severe) LEA.”²

To appreciate this relationship, it is important to first define EA and LEA, outline relevant thresholds, recognize clinical signs that raise suspicion for RED-S, and address the practical challenges in measuring EA in clinical settings.

ENERGY AVAILABILITY AND LOW ENERGY AVAILABILITY: DEFINITIONS AND CLINICAL IMPLICATIONS

EA represents the amount of energy remaining for bodily functions after accounting for exercise energy expenditure (EEE) (refer to Figure 2). When training loads increase, EEE rises, potentially leaving insufficient energy to support essential physiological processes- this state is known as LEA. LEA can lead to adverse health and performance consequences collectively termed RED-S².

While still under examination, there is a general understanding that EA of 30 Kcal/Kg BW in females may be an indicator of LEA. This number is still not well researched in males but < 30 Kcal/Kg BW in males may be used as a clinical guidance that an athlete requires careful examination of his/her energy intake during the preseason, regardless of the presence of apparent signs and symptoms of males/female athlete triad and RED-S². (Refer to Figure 3)

The recent IOC consensus statement on RED-S outlines key criteria emphasizing the close association between RED-S and increased BSI risk². Clinical signs often raise suspicion of LEA or RED-S and include:

• Endocrine and Metabolic:
  • Menstrual dysfunction (e.g., oligomenorrhea or amenorrhea).
  • Low testosterone levels in males.
  • Thyroid dysfunction.
  • Low resting metabolic rate.
• Bone Health:
  • Decreased BMD which increases the risk of stress fractures and osteoporosis and/or low trabecular bone score (TBS)
  • Prolonged recovery times for bone- related injuries.
• Hematological:
  • Anemia and low iron levels.
• Psychological:
  • Mood Disturbances, depression, anxiety and irritability.
• Gastrointestinal:
  • Gastrointestinal distress: nausea, bloating, and constipation.
  • Decreased appetite. 
• Chronic tiredness, not relieved by rest.

SHOULD ENERGY AVAILABILITY BE ASSESSED?

Despite the importance of EA in RED-S diagnosis, accurately calculating or measuring EA in clinical practice remains challenging. This difficulty stems from the time-intensive dietary and exercise assessments and the reliance on precise self-reporting, which may be prone to error or underestimation². Therefore, EA calculations are often supplemented by clinical symptom evaluation and relevant biomarkers. 

Given these challenges, objectively measuring nutritional status in athletes with BSI requires a multifaceted approach. This includes comprehensive clinical evaluation, validated questionnaires, biochemical markers of nutrient status, and consideration of body composition such as Dual-energy X-ray (DXA). These tools collectively aid in identifying athletes at risk of RED-S or LEA and inform targeted nutritional interventions to optimize bone health and injury recovery^7,8 (Table 1).

TAKING A PRACTICAL APPROACH TO BONE HEALTH AND ANERGY AVAILABILITY IN SPORTS NUTRITION

This section outlines practical strategies for assessing and managing bone health in athletes—emphasizing EA and nutrition—and is designed for a multidisciplinary team (MDT) approach (refer to Figure 4). In remote or club settings where a full MDT is not available, once LEA is suspected in an athlete with a confirmed BSI, the club and/or sports medicine physician should collaborate closely with an external sports dietitian—or at minimum a clinical dietitian—even via virtual sessions, to support recovery. A prior body-composition assessment (e.g., BIA) is recommended to inform care. The dietitian can then deliver targeted education on macronutrient and micronutrient needs and guide appropriate day-to-day fueling.

LOOKING AT BODY COMPOSITION IN CONTEXT

When assessing an athlete’s body composition (e.g., via DXA), it is advisable to avoid fixating on a single data point. Obtaining informed consent beforehand and being clear about the purpose is recommended: in this context, DXA helps quantify fat-free mass (FFM) to inform a rough estimate of energy availability and guide clinical decision-making⁶.

Interpreting FFM and fat mass (FM) against appropriate references—sport, age, sex, population, and training phase is advised. For example, endurance athletes generally carry lower FM than power athletes. What matters most are trends over time: Are they losing lean mass unexpectedly? Is FM drifting too low? Such patterns can indicate under-fueling and/or increased training loads that elevate risk.

Rather than treating one body composition result in isolation, it is recommended to integrate it with performance data, bio markers, intake assessments and training context to judge whether the athlete is adapting—or struggling to adapt—over weeks and months⁹. Where resources dictate, a BIA assessment can also be considered. Whatever the method, standardizing the protocol is key (device, analyst, positioning, time of day, hydration status) to ensure results are comparable across visits.

WHEN TO MEASURE RESTING METABOLIC RATE AND TO CALCULATE ENERGY AVAILABILITY

When nutritional assessments and body composition data indicate potential energy deficiency, resting metabolic rate (RMR) testing is recommended. Measured RMR is not directly used in the EA equation but provides a critical validation tool. A suppressed RMR, typically defined as an RMR ratio <0.90 (measured/predicted)—indicates metabolic adaptation to low EA and supports a diagnosis of energy deficiency or RED-S¹⁰. Monitoring RMR alongside EA helps guide nutritional interventions and recovery targets.

Since an EA below 30 kcal/kg FFM (example calculation shown in Table 2) is considered low and flags an athlete at risk for RED-S, a dietitian’s assessment should aim for an EA above 45 Kcal/Kg FFM⁶. Athletes identified with low EA should be promptly referred to a sports dietitian or clinical dietitian for a comprehensive management plan. This is often combined with rest or load modification, tailored nutritional supplementation, and close clinical follow-up.

ASSESSING ATHLETE’S DIETARY INTAKE AND DETERMINING ENERGY INTAKE

Quantifying an athlete’s nutritional intake is vital for identifying deficits contributing to BSIs. Among dietary assessment methods, the 24-hour dietary recall is a practical and time-efficient tool, providing a snapshot of energy intake, macronutrient consumption, especially protein and carbohydrates, and intake of chelators. In a research setting combining a 24-hour recall with a food record is advantageous, however when working in a clinical setting where time of consultation is defined, clinicians will rely on fast methods for quantitative assessments. Table 3 details the differences in dietary assessment methods¹¹.

BENEFITS OF ASSESSING ENERGY, PROTEIN AND CARBOHYDRATE INTAKES

Quantitatively assessing an athlete’s energy, protein and carbohydrate intakes provides the clearest window into whether current fueling supports bone healing and training demands after a BSI. Converting intake to kcal/kg FFM (energy) and g/kg (protein and carbohydrates) helps identify LEA, insufficient protein for bone and connective-tissue remodeling, or mismatched carbohydrate timing that speeds catabolism. These data will guide the dietitian towards targeted education: meal structure, pre/post-session fueling, calcium/vitamin D–rich choices, enabling adjustments as load progresses, and creating objective checkpoints to monitor recovery. It is recommended to repeat the dietary assessment ideally every 4-6 weeks alongside biomarkers and body composition trends. This approach reduces recurrence risk, supports return-to-play quality, and aligns the multi-disciplinary team around measurable goals rather than assumptions².

CHELATOR INTAKE ASSESSMENT AS PART OF THE QUALITATIVE INTAKE ASSESSMENT

Chelators are food compounds that can greatly impair mineral absorption and affect bone health overtime. The sources are varied such as phytates (found in whole grains and legumes) and oxalates (present in spinach and beet greens) – they reduce the bioavailability of key minerals like calcium and iron¹³, exacerbating bone health issues and blood deficiencies. Monitoring chelator intake is particularly important in athletes following plant-based or restrictive diets and adolescents who have increased growth demands. Table 4 expands further on the chelators’ sources and effects, as some are a part of everyday meals and may be overlooked in bone health assessments.

MANAGING LOW BONE MINERAL DENSITY WITH NUTRITION

Athletes presenting with low BMD require careful nutritional management to mitigate further bone loss and support recovery¹¹. Initial treatment focuses on conservative nutritional strategies, such as optimizing meal distribution, energy intake, protein and carbohydrate loads and calcium and vitamin D intake². Iron status, reflected in ferritin and hemoglobin levels, should also be evaluated and corrected if deficient, as iron is essential for bone remodeling.

Table 5 highlights key clinical cutoffs to consider at initial BSI diagnosis. These results become most useful when the sports dietitian integrates them with a quantitative intake assessment (energy, protein, carbohydrate) and a body-composition assessment; this provides a clearer picture of energy availability, nutrient status, and recovery plan.

In addition, when treating BSI cases, meeting daily calcium needs alongside adequate energy and vitamin D is essential for bone mineralization and remodeling. The dietitian should educate the athlete on integrating at least 1000–1500 mg/day of calcium from food-first sources²; this may be distributed through doses of ~300–500 mg per meal and snack. Athletes should be encouraged to prioritize high-bioavailability foods—dairy and fortified alternatives (milk, yoghurt, labneh, calcium-fortified soy or oat drinks), small bony fish (sardines), and lower-oxalate greens (kale, broccoli, bok choy). Calcium intakes increase should be paired with vitamin D repletion (per 25-OH vitamin D labs) to optimize absorption.

If dietary intake falls short, which is common with low energy availability, adding in a calcium supplement to “top up” to target is recommended. It is advisable to split doses and separate the calcium supplement from iron, tea/coffee by 2–4 hours to avoid absorption interference¹³.

MANAGING LOW ENERGY INTAKES, LOW CARBOHYDRATE INTAKES, LOW PROTEIN INTAKES IN PATIENTS WITH BSI

Following quantitative assessment of energy, protein, and carbohydrate intake – alongside interpretation of biomarkers and standardized body-composition trends – clinicians can prioritize targeted nutrition interventions², as outlined in Table 6 (Targeted nutritional strategies in management of BSI cases).

Nutritional goals should be expressed relative to body mass and fat-free mass to enable individualized prescriptions^6,17,18 (e.g., restoring energy availability to approximately 40–45 kcal/kg FFM/day; protein intake of 1.6–2.2 g/kg/day distributed over 4–5 feedings; and carbohydrate intake of 3–7 g/kg/day, adjusted to training load).

Adequate carbohydrate availability is particularly critical during rehabilitation, as higher carbohydrate intake on loading or training days supports glycogen restoration, attenuates excessive cortisol responses, and enhances the insulin-mediated anabolic effect of protein feeding¹⁹. These effects are especially important in the early phases of BSI management, when partial or full immobilization may be required¹¹.

Care should be individualized to the athlete’s readiness for change: for those motivated for change, providing structured plans is beneficial. For others, employing motivational interviewing to build insight around core behaviors (regular meal pattern, inclusion of high-quality protein at each meal, pre-/post-rehab carbohydrate) is recommended as a starting nutritional point of change.

Presenting clear, visualized gaps between current vs required intakes and linking them to symptoms (e.g., fatigue) and relevant biomarkers may also strengthen the athlete’s engagement. Practical tools—including brief meal plans, “healthy plate” visuals, shopping lists, and concise calcium/vitamin D guidance—may facilitate understanding. Progress should be staged using progressive goals (e.g., +300–500 kcal/day, protein distributed at 0.3–0.4 g/kg per meal, carbohydrate escalated on higher-load days), with re-evaluation every 4-6 weeks to adjust prescriptions, confirm adherence, and prevent relapse into LEA. Refer to Table 6 for targeted nutritional strategies in management of BSI cases.

When deficits are clinically significant and compromise quality of life or healing—e.g., iron-deficiency anemia with ferritin ≤20 µg/L, estimated EA <25 kcal/kg FFM/day, or low bone density—coordinate with sports medicine for targeted supplementation if 24-h recalls indicate the athlete is unlikely to meet targets from food alone. This integrated approach helps close urgent nutrient gaps while dietetic education builds sustainable eating patterns for bone healing and safe return to play.

PRACTICAL MILESTONES BEFORE RETURN TO PLAY

Prior to returning to full training or competition, athletes recovering from BSI should demonstrate the below understandings and have a typical eating and fueling pattern as the provided example in Table 7. The checklist below represents the major contributing factors that display athlete’s understanding of performance fueling: 

PUTTING IT ALL TOGETHER: PRACTICAL GUIDANCE FOR SPORTS MEDICINE AND REHABILITATION SETTINGS

Taking a practical approach to bone health and EA means shifting the clinical lens from “what is broken” to “why the bone failed to adapt.” For sports physicians and physiotherapists, nutritional conversation is part of the treatment plan. When LEA is suspected, the message is to collaborate early with a sports or clinical dietitian, even if remotely as per Figure 5. Improving fueling consistency and body-composition stability are the nutritional milestones of recovery in BSI.

• First-line strategies include increasing energy intake, supplementing deficient micronutrients, and adjusting interventions based on the injury stage and sport demands.
• Continued intake assessments using dietary recalls or food records help detect early signs of recurrent LEA.
• Education sessions focusing on the importance of balanced energy intake, nutrient timing, and minimizing chelator effects can empower athletes to maintain bone health long-term.

 Nelda Nader RD, MSc, IOC Dip Sports Nutr

Shaikha Mahmoud Abdulla RD, IOC Dip Sports Nutr

Amna Hamad AlSulaiti RD, Dip IOPN

Aspetar Orthopaedic and Sports Medicine Hospital

​Doha, Qatar

Contact: nelda.nader@aspetar.com

References

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