Inducing low energy availability in trained endurance male athletes results in poorer explosive power
Protocol
Intervention study: energy availability reduced by 25% for 14 consecutive days in 12 trained, well-trained and elite male endurance athletes, by increasing energy expenditure and controlling energy intake; no control group is described in the abstract (from the abstract)
After the intervention: blood draw for health markers, body composition, resting energy expenditure, three performance tests (endurance, agility, explosive power) and two questionnaires (Three Factor Eating Questionnaire, Well-being questionnaire)
Key Findings — Participants & Key Findings
n=12 trained, well-trained and elite male endurance athletes, previously healthy.
Energy availability cut by 25% for 14 consecutive days (more expenditure + controlled intake); achieved 22.4±6.3 kcal/kg FFM/day.
Explosive power fell (p=0.001); lactate metabolism was altered.
Haemoglobin fell (p=0.022); iron and IGF-1 tended lower (p=0.066, p=0.077).
Well-being worsened (p=0.036); cognitive dietary restraint correlated with energy availability (r=0.528).
Resting energy expenditure did not change and the authors saw the power loss before any hormonal change.
Practical Application
In 12 trained-to-elite male endurance athletes, cutting energy availability by 25% for 14 days (to ~22 kcal/kg FFM/day) reduced explosive power, lowered haemoglobin and worsened well-being, before resting energy expenditure or hormones changed — in men too, a two-week moderate deficit costs performance early, so don't wait for hormonal or metabolic signs.
When chasing body-fat loss, train-low (REF-543) or time-restricted eating (REF-520), keep overall energy availability adequate and periodise any deficit rather than holding it. The ≥30 kcal/kg FFM/day threshold is not this study's: it comes from REF-342 (29 sedentary young women, 5 days, LH pulsatility) — how it transfers to trained athletes and men is inference; REF-341 frames low energy availability as a continuum.
Falling power, worse mood and fatigue during a deficit are reasons to review intake; this study measured power, haemoglobin and well-being, not libido or illness.
Limitations
Small sample (n=12), no control group, short-term (14 days); long-term effects not studied.
Adult trained men, not specifically masters 40+.
Induced LEA under controlled conditions ≠ real chronic underfueling.
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B+: uncontrolled pre–post, n=12
Content correction 2026-09-27
Journal "Vol. 121(6)" -> Vol. 122(2), pp. 503-513 (online 2021).
Vague "changes in health markers/hormones" -> haemoglobin fell, iron and IGF-1 trended lower, well-being worsened, resting energy expenditure unchanged, no hormonal change yet; achieved EA 22.4 kcal/kg FFM/day added.
Sport "running, sprint" -> general (endurance athletes, sport not specified); Tier 3-4 -> 2-4; Level B+ -> B (uncontrolled pre–post, n=12).
2026-09-28: added Protocol from the abstract (Europe PMC/PubMed PMID 34825937).
2026-09-29: the ≥30 kcal/kg FFM threshold was attributed to a range "REF-341-345"; it comes from REF-342 (sedentary women) — attributed precisely, transfer labelled.