2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs)
Key Findings — Core Definitions
REDs = a syndrome of deleterious health and performance outcomes in female and male athletes exposed to low energy availability (LEA) — inadequate energy intake in relation to exercise energy expenditure (first introduced by the IOC in 2014).
Energy Availability (EA) = (Energy Intake − Exercise Energy Expenditure) / Fat-Free Mass, in kcal/kg FFM/day.
The 2023 statement frames LEA exposure as problematic or adaptable, modulated by individual moderating factors, in a new Physiological Model — rather than as a single cut-off. Since 2018 there have been >170 original REDs publications, including emerging data on the role of low carbohydrate availability, the interplay between mental health and REDs, and the impact of LEA in males.
Not from this paper: the EA threshold numbers the base uses — LH pulsatility disrupted below 30 kcal/kg LBM/day, with 45 as the balanced reference — come from the Loucks & Thuma experiment, REF-342. The 2023 abstract states no threshold.
Affected Systems (2023 update)
The statement updates the Health and Performance Conceptual Models. Health outcomes by spoke, with examples of impairment (accepted-manuscript full text, checked 2026-09-28: Table 2; performance outcomes from Table 3):
| System | Consequence |
|---|---|
| Reproductive | Females: altered LH concentrations or pulsatility, ↓ oestrogen and progesterone, primary or secondary amenorrhea, oligomenorrhea, luteal-phase defects, anovulation; males: ↓ testosterone, sperm abnormalities, erectile dysfunction; both: ↓ libido |
| Bone | loss of BMD or lack of expected accrual, low BMD Z-score, impaired bone strength or micro-architecture, bone stress injuries, changed bone-remodelling biomarkers |
| Energy metabolism | low T3, low RMR / RMR ratio, ↓ leptin, ↑ cortisol |
| Growth and development | ↓ IGF-1, ↑ GH / GH resistance, deviation from the expected growth curve |
| Immune | ↑ infection/illness susceptibility, changed immune biomarkers |
| GI | abdominal pain, cramps, bloating, altered bowel movements |
| Cardiovascular | ECG abnormalities (e.g., sinus bradycardia, QT prolongation), hypotension / orthostatic hypotension / syncope, impaired endothelial function, cardiac abnormalities |
| Glucose and lipid metabolism | ↓ fasting/24-h glucose and insulin, ↑ total/LDL cholesterol |
| Mental health | depression, exercise dependence/addiction, disordered eating / eating disorders |
| Neurocognitive | impaired memory, decision making, spatial awareness, planning, executive function |
| Sleep | self-reported sleep disturbances |
| Skeletal muscle | ↓ muscle protein synthesis, ↓ glycogen restoration |
| Urinary | urinary incontinence |
| Performance | ↓ athlete availability (training days lost to illness or injury), ↓ training response, ↓ recovery, ↓ cognitive performance/skill, ↓ motivation, ↓ muscle strength, ↓ endurance performance |
| Haematological | low iron status, ↑ hepcidin, ↓ iron absorption, ↓ haemoglobin concentration/mass, ↓ response to altitude training |
Diagnostic Signals (screening)
Indicators from the statement's IOC REDs CAT2 Severity/Risk Assessment Tool (accepted-manuscript full text, checked 2026-09-28: Table 4; the abstract says only that knowledge of REDs signs and symptoms has been updated):
Female: primary amenorrhea, or prolonged secondary amenorrhea (≥12 missed cycles) due to FHA (severe primary indicator); secondary amenorrhea (3-11 missed cycles) due to FHA (primary); oligomenorrhea due to FHA, >35 days between periods and at most 8 periods/year (secondary); lack of ovulation (potential)
Male: clinically low free or total testosterone (severe primary indicator) or sub-clinically low, in the lowest quartile of the reference range (primary); low libido and decreased morning erections are emerging potential indicators
Both sexes: ≥1 high-risk or ≥2 low-risk bone stress injuries in the previous 2 years, or ≥6 months out of training for BSI (primary), 1 low-risk BSI (secondary); BMD Z-score <-1 or a fall from prior testing (primary); deviation from a young athlete's growth trajectory (primary); elevated EDE-Q score or a diagnosed eating disorder (primary); diagnosed depression and/or anxiety (secondary); potential indicators — GI or liver dysfunction, urinary incontinence (females), symptomatic orthostatic hypotension, bradycardia, low blood pressure, sleep disturbances, psychological symptoms, exercise dependence, low BMI.Athlete-reported symptoms include hunger and performance or training plateaus or declines
Labs (non-exhaustive): sub-clinically or clinically low T3 (primary); elevated total or LDL cholesterol (secondary); potential indicators — low IGF-1, low blood glucose, low blood insulin, poor or declining iron studies (e.g., ferritin) and/or haemoglobin, elevated cortisol, low RMR (<30 kcal/kg FFM/d or RMR ratio <0.90)
Body composition
The statement includes guidelines for safe and effective body composition assessment as a REDs-prevention measure (abstract); the specific protocol is not reproduced here.
CAT2 — the IOC REDs Clinical Assessment Tool, Version 2
The tool has its own companion paper by a subgroup of this consensus: *Stellingwerff T, Mountjoy M, McCluskey WTP, Ackerman KE, Verhagen E, Heikura IA, 2023. Review of the scientific rationale, development and validation of the IOC REDs Clinical Assessment Tool V.2. Br J Sports Med 57(17):1109-1121. DOI 10.1136/bjsports-2023-106914, PMID 37752002.* The points below are checked against that paper's abstract.
Three steps: (1) initial screening; (2) severity/risk stratification from any identified REDs signs and symptoms, using weighted primary and secondary indicators; (3) a physician-led final diagnosis and treatment plan, developed with the athlete, the coach and the wider health and performance team.
Four levels. CAT2 introduces a more clinically nuanced four-level traffic light — green, yellow, orange, red — each with associated sport-participation guidelines.
Indicators are weighted and scored. Primary and secondary REDs indicators were weighted for scientific support, clinical severity/risk, and methodological validity and usability, allowing objective scoring of athletes on the presence or absence of each.
Validation path: early drafts were athlete-tested, fed back and refined; then validated by REDs experts through voting statements; then assessed by physicians and practitioners for validity and usability.
The indicator list is in this statement's Table 4 (severe primary, primary, secondary and potential indicators; summarised under Diagnostic Signals above). What this base does NOT hold: the criteria that separate the four colours and the participation rules attached to each level — they are in this statement's Figure 6, with a scoring tool in its appendix 5, and are deliberately not reproduced here (accepted-manuscript full text, checked 2026-09-28).Do not reconstruct or estimate them — the correct answer to "which colour am I" is a referral.
Treatment / Management
Primary principle (abstract): prevention and treatment principles are presented for sports organisations and clinicians; the core of treatment is restoring energy availability — more intake and/or less expenditure.
Not from this paper; the base's own practice: monitor menstrual return (female), morning HR and bone health with the athlete's clinician; use formal eating-disorder screening and psychological support when indicated. Recovery timelines for reproductive function and bone are not stated in the abstract and are not given here.
Practical Application
The 2023 IOC consensus defines REDs as the health and performance syndrome produced by low energy availability in female AND male athletes, now framed as problematic vs adaptable LEA exposure with individual moderators, and introduces the physician-led CAT2 tool for diagnosis and participation decisions. Before any training-block diagnosis of "overtraining" or "stagnation", rule out LEA — it mimics overtraining but needs fuelling, not rest.
Female athletes: a missed cycle is an LEA signal until proven otherwise (even on hormonal contraception — OCP can MASK amenorrhea; see REF-338).
Male athletes: low free or total testosterone is the male primary indicator (severe when clinically low); low libido and decreased morning erections are emerging potential indicators (accepted-manuscript full text, checked 2026-09-28: Table 4 and text).
Not from the consensus abstract; the base's own practice: do not prescribe caloric restriction and hard training at the same time in an athlete aiming at performance gains.
Do not assign a REDs severity level yourself. CAT2 is a four-level, physician-led instrument with weighted indicators and score thresholds this base does not hold; naming a colour, a risk level or a participation rule without it is invention. Screen, name the concern, refer.
Limitations
The CAT2 steps, levels and validation path above are from the companion paper's abstract; its full text was not read. The indicator list is in this statement's Table 4; the colour criteria and per-level participation rules (this statement's Figure 6) are deliberately absent from this entry rather than approximated (accepted-manuscript full text, checked 2026-09-28).
The systems table and screening list are from the full text (Tables 2-4) (accepted-manuscript full text, checked 2026-09-28); the abstract describes them only as updated conceptual models.
EA as a metric has high measurement error in free-living athletes (food logs and expenditure estimates); the abstract gives no error figures.
The base's EA threshold comes from female laboratory work (REF-342); the 2023 statement's own position is a continuum with individual moderators, not a cut-off.
Most underlying evidence is observational and cross-sectional; causal intervention RCTs are few and small.
How this entry was checked and changed
Content correction 2026-09-27
EA bands "≥45 optimal / 30-45 subclinical / <30 clinical" -> not in the 2023 abstract, which frames LEA as problematic vs adaptable exposure; the 30/45 figures are now attributed to REF-342 (Loucks & Thuma) under "Not from this paper".
"exposure ≥ ~5 days", "amenorrhea ≥3 consecutive months", "≥3 URTI/year", "BMD every 6-12 months", "reproductive recovery 6-12+ months, BMD 2-3 years", "food logs ±20%, EEE ±10-15%", "male threshold ~25-35", "REDs at 35-40" -> none in the abstract; removed.
Systems table and screening list kept but labelled full text; added the abstract's points on low carbohydrate availability, mental health, males, the Physiological Model and body-composition guidelines.
2026-09-28: lines labelled "full text; not checked" read against the open-access accepted manuscript (Brage NIH via NVA, nva.sikt.no): 0 confirmed, 16 corrected (systems table rebuilt from Table 2/3: 'Endocrine' split into energy metabolism and growth, ghrelin removed, GI 'constipation, gastroparesis' -> abdominal pain/bloating/bowel changes, immune 'URTI, mucosal immunity' -> infection susceptibility/immune biomarkers, five missing spokes added; screening list rebuilt from Table 4 CAT2 indicators: 'unexplained fatigue', cold intolerance, hair thinning, weight instability, low vitamin D, low LH pulsatility and 'despite supplementation' removed; male signal = low testosterone primary, libido/morning erections potential), 0 removed.
2026-09-28: CAT2 lines corrected against the open-access accepted manuscript (Brage NIH via nva.sikt.no): the indicator list is in this statement's Table 4, not only in the companion paper; colour criteria and participation rules (Figure 6) still deliberately not reproduced; Limitations updated to match.
2026-09-29: "Never prescribe caloric restriction + hard training" read as the consensus's finding; it is the base's practice — labelled.
2026-10-01: cross-reference repointed from a merged framework to the one that replaced it (SYNTH-01→31, 05→34, 09→70, 12/15→32, 19→26).