Dual-Energy X-Ray Absorptiometry per Cent Fat Z-Score as a Predictor of Menstrual Status in Adolescent and Young Adult Female Athletes

Why It Matters

The finding offers clinicians a superior, individualized metric to guide weight‑restoration strategies and reduce menstrual dysfunction in female athletes, addressing a key health risk of relative energy deficiency in sport.

Key Takeaways

• DXA %fat Z‑score outperforms BMI in detecting amenorrhea
• Cut‑off < −1.0 raises sensitivity to ~69 %
• Specificity slightly lower but remains acceptable
• BMI/%EBW miss many at‑risk athletes
• Target Z‑score ≥ −1.0 may guide RED‑S therapy

Pulse Analysis

Relative Energy Deficiency in Sport (RED‑S) remains a hidden threat to female athletes, often manifesting as amenorrhoea or oligomenorrhoea. Traditional weight‑based targets such as BMI ≥ 18.5 kg/m² or % EBW ≥ 90 % fail to capture the unique body‑composition profile of high‑performance athletes, whose lean mass skews these indices. Dual‑energy X‑ray absorptiometry (DXA) provides precise % fat measurements, and when expressed as an age‑ and ethnicity‑matched Z‑score, it offers a standardized view of adiposity relative to peers, creating a more nuanced tool for assessing energy availability.

In the Boston cohort, a % fat Z‑score below −1.0 identified nearly 70% of athletes with amenorrhoea and over half of those with oligomenorrhoea, far surpassing the 30% detection rate of conventional BMI or % EBW cut‑offs. Although specificity dipped slightly, the trade‑off yields a clinically valuable early‑warning signal, enabling practitioners to intervene before hormonal suppression escalates. By adopting the Z‑score threshold, sports medicine teams can set realistic, individualized weight‑restoration goals that align with each athlete’s physiological baseline rather than generic population norms.

The broader implication is a shift toward data‑driven, athlete‑specific monitoring. Integrating DXA‑derived % fat Z‑scores with hormonal panels, training load metrics, and nutrition assessments could refine RED‑S diagnostics and personalize treatment pathways. Future research should develop sport‑specific reference databases and explore longitudinal changes in Z‑score alongside menstrual recovery. Until then, clinicians are encouraged to incorporate DXA assessments judiciously, respecting mental‑health considerations, to better safeguard the reproductive health and performance longevity of female athletes.