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Low energy availability in recreational high-intensity functional training athletes: associations with health and performance outcomes

Gabriella Vlattas, Xuewen Wang, Andrew Ortaglia, Siqi Hong, Toni Marie Torres-McGehee · Frontiers in Nutrition · 2026

This study measured energy availability (calories eaten minus calories burned relative to body composition) and various health and performance measures in 30 recreational high-intensity functional training athletes over two weeks. Despite finding that many participants had low energy availability, the researchers did not detect significant differences in health or performance outcomes over this short timeframe, suggesting that negative effects may take longer to appear.
Takeaway: Continue monitoring your energy intake and exercise expenditure if you do high-intensity functional training, as low energy availability may have long-term consequences even if short-term effects aren't obvious.
Abstract (source)

Introduction: Low energy availability (LEA) is the primary etiological factor underlying Relative Energy Deficiency in Sport (RED-S), yet limited research has examined LEA risk and associated health and performance outcomes in recreational high-intensity functional training (HIFT) athletes. The

Purpose: of this study was to evaluate energy availability (EA) and physiological outcomes aligned with the RED-S Health and Performance Models in a recreational HIFT cohort.

Methods: Thirty participants (females: n = 18, males: n = 12; 31.2 ± 8.2 years) completed two-week prospective observational study with repeated measures of energy intake, exercise energy expenditure, and associated health and performance-related measures. Energy intake was assessed via dietary logs, exercise energy expenditure was estimated using a wearable armband, and EA was calculated relative to dual-energy X-ray absorptiometry–derived fat-free mass. Participants were classified as LEA if EA was 0.05), and EA was not significantly correlated with performance or health outcomes. In an exploratory analysis, sleep duration was moderately positively associated with TQR ( ρ = 0.46, p = 0.01); however, this finding should be interpreted cautiously given the number of comparisons performed.

Discussion: Despite the high prevalence of LEA, associated health and performance impairments were not detected, suggesting that measurable consequences of LEA may not be evident over a short observation period in recreational HIFT athletes. These

Findings: support ongoing monitoring of EA, fueling practices, and recovery behaviors to reduce the potential long-term consequences associated with RED-S.

Observational / cohortOpen accessRecovery & SleepVelocity-Based & Technology
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