Short-Term Severe Low Energy Availability in Athletes: Molecular Mechanisms, Endocrine Responses, and Performance Outcomes-A Narrative Review.
Level 5 - mechanism / opinion, no new human data
Narrative review without systematic search or quantitative synthesis.
PubMed 40539747 · doi:10.1111/sms.70089
What was done
This narrative review characterized the effects of short-term (days to weeks) severe (< 30 kcal/kg fat-free mass/day) low energy availability on exercise performance, physiological parameters, and endocrine responses. The review focused primarily on female athletes due to higher reported prevalence and available literature, while also briefly assessing emerging evidence and potential sex differences in male athletes.
What was found
The abstract reports no numerical values or statistical effect sizes. Qualitatively, short-term severe low energy availability was reported to trigger energy-conserving responses including suppression of the hypothalamic-pituitary-ovarian axis, reductions in triiodothyronine and insulin-like growth factor I, reduced resting metabolic rate, compromised protein turnover in collagen-rich tissues, suppressed muscle protein synthesis, elevated cortisol, altered immune function, increased exercise fat utilization, and direct decrements in power, sprinting, and endurance exercise performance despite reductions in body mass.
Why it matters
These findings challenge the assumption that body mass reduction inherently improves power-to-mass ratios and athletic performance, highlighting rapid physiological trade-offs from acute energy deficits.
Limits
As a narrative review, it lacks systematic search methodology, formal study quality assessment, and pooled effect estimates. No quantitative values or sample sizes are reported in the abstract, and the underlying evidence base remains predominantly focused on female athletes.
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