Biochemical Responses to Experimentally Induced Short-Term Low Energy Availability in Athletes: A Systematic Review.
Level 1 - systematic review of randomized trials
Systematic review of experimental intervention studies
PubMed 41794545 · doi:10.1111/sms.70249
What was done
A systematic review was conducted per PRISMA guidelines searching PubMed, Web of Science, and Scopus for experimental studies examining the short-term (>24 hours) biochemical effects of experimentally induced low energy availability (LEA) in athletic populations using pre-post assessments. Outcomes included biomarkers of bone metabolism, calcium metabolism, energy regulation, inflammation, iron status, sex hormones, and thyroid function. Thirteen experimental studies encompassing 145 participants were included.
What was found
Leptin consistently decreased following LEA. Approximately half of the interventions showed significant increases in the bone resorption marker βCTX-1 and reductions in the bone formation marker P1NP. Testosterone decreased in 50% of interventions. IGF-1 and T3 remained stable in most studies, and no consistent changes were identified in estradiol, progesterone, calcium metabolism, inflammatory markers, or iron status. No numerical effect sizes or confidence intervals were reported in the abstract.
Why it matters
This synthesis demonstrates that metabolic and bone turnover adaptations occur rapidly following brief periods of energy deficiency in athletes, identifying key early biomarkers of Relative Energy Deficiency in Sport (RED-S).
Limits
The total sample size across 13 studies was small (145 participants, average ~11 per study). Interventions frequently co-occurred with low carbohydrate availability, confounding the specific effect of energy deficit versus carbohydrate restriction. The abstract does not report pooled quantitative effect sizes, and protocols lacked standardization across sexes.
Cited by
- context Excessive carbohydrate restriction combined with excessive exercise impairs thyroid function, testosterone production, and joint proteoglycans.