Effects of Individualised Nutrition on Performance and Athlete Triad Risk

Background. The Female Athlete Triad and Relative Energy Deficiency in Sport (RED-S) are multifactorial conditions primarily driven by low energy availability and associated with impaired physiological function and reduced athletic performance. Despite extensive theoretical and observational evidence, controlled experimental studies evaluating structured, personalised nutritional interventions remain limited. Objectives. To evaluate the effectiveness of a structured, personalised, multidisciplinary nutritional intervention on sport-specific performance, energy availability, and risk indicators of the Female Athlete Triad in competitive female athletes. Material and Methods. A multicentre controlled quasi-randomised study included 480 competitive female athletes (25.1 ± 4.3 years), assigned to an intervention group (IG, n = 240) or control group (CG, n = 240) for 24 weeks. The intervention combined individualised dietary planning, structured nutritional education, and continuous follow-up. Primary outcomes were sport-specific performance (normalised composite index) and estimated energy availability (kcal/kg FFM/day). Secondary outcomes included Triad risk (LEAF-Q ≥ 8), eating behaviour (EDE-Q), nutritional knowledge (NSKQ), and body composition (DXA). Mixed-effects and multivariate regression models were applied (p < 0.05). Results. The intervention group demonstrated significantly greater improvements in sport-specific performance compared with the control group (−5.8% ± 3.1 vs −0.9% ± 2.8; β = −0.31; 95% CI −0.42 to −0.20; p < 0.001), with a large standardized effect size (Cohen’s d = 1.66). Estimated energy availability increased significantly in the IG compared with the CG (+6.3 ± 5.9 vs +0.8 ± 4.7 kcal/kg FFM/day; β = 0.28; 95% CI 0.19–0.37; p < 0.001; Cohen’s d = 1.03).The prevalence of Triad risk (LEAF-Q ≥ 8) decreased from 30.4% to 18.0% in the IG compared with 29.2% to 27.9% in the CG (OR = 0.49; 95% CI 0.34–0.71; p < 0.001). Significant improvements were observed in eating behaviour (EDE-Q: β = −0.24; 95% CI −0.35 to −0.12; p = 0.002) and nutritional knowledge (NSKQ: β = 0.41; 95% CI 0.29–0.53; p < 0.001). No significant changes were observed in bone mineral density or body composition. Conclusions. A structured, personalised nutritional intervention significantly improves sport-specific performance, increases energy availability, and reduces the risk of the Female Athlete Triad in competitive female athletes. These findings provide experimental evidence supporting the implementation of multidisciplinary, individualised nutritional programmes as an effective strategy for improving both health and performance in women’s sport.