REF-520 · Moro et al., 2020 · Journal of the International Society of Sports Nutrition, Vol. · Paper
Time-Restricted Eating (8-h window) in elite under-23 cyclists
Performance maintained, weight and fat down, anabolic hormones down (RCT)
Participants & Protocol
n=16 elite under-23 cyclists, randomly assigned to TRE or a normal-diet control (ND)
Protocol
Parallel randomized controlled trial during 4 weeks of high-level endurance training: time-restricted eating (TRE) vs a control group (ND) (from the abstract).
TRE: 100% of estimated daily energy needs in an 8-h window (10:00-18:00); ND: energy spread over 3 meals between 07:00 and 21:00
4 weeks of high-level endurance training
Measures: fat and fat-free mass (bioelectrical impedance), VO2max and basal metabolism (indirect gas analysis), performance tests, blood counts, free testosterone, IGF-1, IL-6, TNF-α
Key Results
With TRE, body weight fell (−2%, p=0.04) and so did fat-mass percentage (−1.1%, p=0.01), while fat-free mass did not change
Performance tests: no significant between-group differences; peak power output/body weight (PPO/BW) improved in TRE because of the weight loss (p=0.02)
Free testosterone (p=0.01) and IGF-1 (p=0.03) decreased significantly in the TRE group
Immune/inflammation: leucocyte count fell in ND (p=0.02); the neutrophil-to-lymphocyte ratio fell in TRE (p=0.03)
Authors' conclusion: an 8-h window elicits weight loss, improves body composition and raises PPO/BW in elite cyclists; may reduce inflammation and protect some immune components; could be a component of a periodised nutrition plan
Practical Application
In 16 elite under-23 cyclists, 4 weeks of an 8-h eating window (10:00-18:00) at 100% of estimated energy needs cut body weight 2% and fat-mass percentage 1.1% with fat-free mass unchanged, left performance no different from controls and raised PPO/BW (p=0.02) — but free testosterone and IGF-1 fell significantly. A short-term body-composition tool with an anabolic-hormone cost signal, not a proven long-term strategy.
The trial fed 100% of estimated needs inside the window; inference, not tested: in practice a compressed window often becomes a spontaneous deficit — then the LEA/REDs risk applies (REF-341)
Not from this paper; the base's own practice: do not combine TRE with an aggressive deficit during heavy training phases, and place long/intense sessions where the eating window can fuel them
Inference, not tested: the falls in free testosterone and IGF-1 are the reason to treat TRE as a periodised block, not a permanent state
Limitations
n=16, 4 weeks (short-term); elite under-23 men only, not masters/women
Energy intake set at 100% of estimated needs; both groups followed the same 7-day diet plan at 4800 kcal with identical macros (719.0 g carbohydrate, 158.0 g protein, 163.0 g fat), differing only in meal timing (corrected 2026-10-12, full text); body composition by bioelectrical impedance
Free testosterone and IGF-1 decreased — the long-term meaning for adaptation is untested
Long-term sustainability and effects on training adaptation not studied
How this entry was checked and changed
Why this level
regraded 2026-09-27 from A: parallel RCT, n=16
Content correction 2026-09-27
Type "RCT | Level A" -> parallel RCT with n=16; Level A -> B per KB-LEVEL-RUBRIC. "Elite/keirin cyclists" -> elite under-23 cyclists (keirin is not in the abstract). Sport "cycling, running" -> cycling. Tier 4-5 -> Tier 3-4.
"Isocaloric (same calories/macros, only timing differed)" -> the abstract says TRE consumed 100% of estimated needs in the window and ND ate 3 meals; macros were not stated as matched in the abstract, but the full text gives both groups the same 4800-kcal plan with identical macros, differing only in meal timing, so the original "isocaloric, only timing differed" holds for the diet plan (corrected 2026-10-12, full text).
Added the omitted result that free testosterone and IGF-1 decreased significantly in TRE, plus the weight (−2%), fat-mass (−1.1%), PPO/BW and NLR numbers; "improvement in some metabolic/inflammatory markers" made specific.
2026-09-28: added Protocol heading and design bullet from the abstract (Europe PMC PMID 33308259).
2026-09-29: cross-reference range "REF-341-345" replaced with REF-341 (the REDs consensus).
Full text (checked 2026-10-12)
Participants were 16 healthy young men (19.3 ± 0.1 years) from 5 elite teams with at least three seasons in an elite team, allocated TRE n = 8 and ND n = 8, who rode 13,500 ± 1500 and 13,000 ± 1500 km in the previous season (full text, Table 1).
Training in the winter pre-competition season was 500 ± 50 km/week in 6 sessions per week, mostly long steady rides at mild/medium pace, held within the 10 a.m.-6 p.m. feeding window (full text).
Correction: the entry says energy was "not measured as isocaloric between groups" and that macros were not stated as matched, but the paper gave all athletes the same 7-day diet plan at 4800 kcal (719.0 g carbohydrate, 158.0 g protein, 163.0 g fat; 62.9/14.3/30.6% of energy), differing only in meal timing (full text, Table 2).
Body mass fell from 67.04 ± 5.03 to 65.78 ± 4.93 kg in TRE versus 72.28 ± 6.24 to 72.50 ± 6.45 kg in ND, and relative fat mass went from 9.59 ± 0.77 to 8.52 ± 1.21% in TRE versus 10.65 ± 2.24 to 10.77 ± 0.97% in ND; these within-group fat changes were not significant, with p = 0.01 a main effect of diet (full text).
PPO went from 407.50 ± 41.66 to 415.00 ± 39.28 W in TRE and 411.25 ± 35.63 to 403.75 ± 29.73 W in ND, PPO/BW from 6.08 ± 0.51 to 6.31 ± 0.46 versus 5.71 ± 0.55 to 5.60 ± 0.53 W/kg, and VO2max from 71.98 ± 3.93 to 69.94 ± 8.66 versus 68.30 ± 7.19 to 67.17 ± 4.59 ml/kg/min (full text, Table 3).
Free testosterone fell 27% in TRE (33.73 ± 7.56 to 24.33 ± 7.23 pg/mL, p = 0.006) versus 41.51 ± 14.09 to 38.33 ± 12.60 pg/mL in ND (full text, Table 4).
The text reports IGF-1 decreased 12% in TRE (p = 0.03), but Table 4 lists TRE IGF-1 as 244.03 ± 90.83 pre and 291.60 ± 58.29 ng/mL post (full text, Table 4).
Resting energy expenditure fell ~10% in TRE (1992 ± 251 to 1772 ± 147 kcal/day) and ~2% in ND, without a significant interaction (full text, Table 3).