REF-151 · Witard et al., 2025 · Sports Medicine, Vol. 55, pp. 1361-1376 · Paper

Protein Nutrition for Endurance Athletes: A Metabolic Focus on Promoting Recovery and Training Adaptation

Astrong evidenceMeasured on a mixed groupWritten before October 2026, being re-checked

Key Findings

1. Daily protein intake for endurance athletes (the review's recommendations):

ContextRecommendation
Habitual intake (typical, male and female endurance athletes)~1.5 g/kg/day
Advocated daily intake~1.8 g/kg/day
Carbohydrate-restricted training periodsmay exceed 2.0 g/kg/day in the abstract; Table 1 targets 1.95 g/kg/day on training days with low CHO availability (corrected 2026-10-12, full text)
Rest daysmay exceed 2.0 g/kg/day
The 1.8 g/kg figure rests on a series of contemporary protein-requirement studies (IAAO-type; see REF-156, REF-152); habitual ~1.5 g/kg sits below it.

2. Per-meal protein: the abstract says definitive per-meal guidelines cannot yet be given — there are too few metabolic studies of the dose-response of muscle protein synthesis to protein ingestion after endurance exercise to give definitive per-meal amounts for endurance athletes.

But the Key Points and Table 1 give a preliminary target of ~0.5 g/kg per meal, as a 0.5 g/kg protein feed in immediate post-exercise recovery, based on a single study (maximally effective dose 0.49 g/kg, 95% CI 0.26–0.72) (corrected 2026-10-12, full text).

3. Protein with carbohydrate around exercise: no compelling evidence that co-ingesting protein with carbohydrate before or during endurance exercise improves performance, or that it speeds liver or muscle glycogen resynthesis in recovery, at least when carbohydrate recommendations are met.

4. Where protein matters more: recent evidence suggests a role for protein nutrition in optimising the adaptive metabolic response to endurance training under low carbohydrate and/or low energy availability — the increasingly popular periodised (train-low) strategies.

**5.

Metabolic background (full text, checked 2026-09-27):** endurance exercise oxidises amino acids (~6% of its energy cost, branched-chain preferentially), part of why athletes need more protein than sedentary adults; the EAA content of a protein source, not gross protein alone, dictates the metabolic response; endurance exercise stimulates mitochondrial protein synthesis with minimal acute change in myofibrillar synthesis; protein attenuates post-exercise protein breakdown in catabolic states such as energy restriction.

Practical Application

**Narrative review (Witard, Hearris & Morgan 2025): endurance athletes habitually eat ~1.5 g/kg/day of protein; the evidence supports ~1.8 g/kg/day, rising above 2.0 g/kg/day during carbohydrate-restricted training and on rest days in the abstract (Table 1 targets: 1.95 g/kg/day on low-CHO training days, 2.0 on recovery days).Per-meal targets are only preliminary (~0.5 g/kg per meal, e.g. right after exercise, from a single study) (corrected 2026-10-12, full text), and adding protein to adequate carbohydrate before, during or after exercise brings no performance or glycogen benefit.** Get the daily total right first; the day you cut carbohydrate or rest is the day protein should go up, not down.
Multiply body mass by 1.8 for a normal training day and by 1.95 for a train-low day and 2.0 for a rest day (Table 1; the abstract says either may exceed 2.0) (corrected 2026-10-12, full text); most endurance athletes are ~0.3 g/kg short of the first number.
Train-low / sleep-low blocks and energy deficits are where protein does its most useful work in this review — protect the adaptive response and the muscle, not the session.
Don't expect protein in bottles or gels to improve performance or glycogen restoration if you are already hitting carbohydrate targets.
Not from this review: per-meal amounts such as 30-40 g × 4-5 meals — the abstract says the endurance dose-response data for definitive per-meal amounts do not yet exist, while the Key Points and Table 1 give a preliminary ~0.5 g/kg per meal, as a 0.5 g/kg feed in immediate post-exercise recovery (single study) (corrected 2026-10-12, full text); pre-sleep casein → REF-155; masters upper bound → REF-348.

Limitations

Narrative review, not a systematic one. Study selection and weighting are the authors' judgement; the A level reflects authorship and currency rather than a reproducible search.
Mechanistic focus on muscle protein synthesis — a surrogate. MPS responses do not reliably predict performance or body-composition outcomes over a training block.
Recommendations are synthesised across mixed populations and mostly male samples; sex-specific requirements are addressed separately and later (REF-725).
The claim that free amino acids stimulate MPS more efficiently than intact protein is an acute-kinetics observation and is not a recommendation to replace food with supplements.
No dose-response for endurance athletes on hard versus easy days is settled here; see REF-726 for the train-low interaction.
How this entry was checked and changed
Content correction 2026-09-27
"Recovery day 2.0 g/kg", "Train-Low day 1.95 g/kg" -> the review's abstract says the requirement may exceed 2.0 g/kg/day during carbohydrate-restricted training and on rest days [its Table 1 targets 1.95 g/kg/day on low-CHO training days and 2.0 on recovery days (corrected 2026-10-12, full text)].
Athlete-specific lead ("82→78 kg athlete: 144/160/156 g") -> generic finding from the abstract.
"4-5 meals × 30-40 g", "30-40 g within 1-2 h post-training" -> not from this review (definitive per-meal guidelines not established per the abstract; the Key Points and Table 1 give a preliminary ~0.5 g/kg per meal and a 0.5 g/kg post-exercise feed (corrected 2026-10-12, full text)); added the review's null on protein + carbohydrate for performance/glycogen when CHO is adequate.
Four-roles section marked as full text, not checked against the abstract.
Lines labelled "full text; not checked" were read against the open-access full text (PMC12152099): 1 corrected to what the paper says.
Full text (checked 2026-10-12)
The review's practical guidelines set daily targets of 1.80 g·kgBM−1·day−1 on standard training days (1.90 g·kgBM−1·day−1 may be considered for female individuals in the luteal phase), 2.0 g·kgBM−1·day−1 on recovery days and 1.95 g·kgBM−1·day−1 on training days with low CHO availability (full text, Table 1).
Correction: the entry says the requirement "may exceed 2.0 g/kg/day" during carbohydrate-restricted training; the review's Table 1 says to "target a dietary protein intake of 1.95 g·kgBM−1·day−1 on training days conducted with low CHO availability", based on an IAAO estimate from a 10-km treadmill run (full text, Table 1).
Correction: the entry says the review "does not set per-meal guidelines"; its Key Points say "Preliminary evidence indicates that endurance athletes should target a per meal protein intake of ~ 0.5 g·kgBM−1", and Table 1 recommends "a protein feed of 0.5 g·kgBM−1 during immediate post-exercise recovery" (full text, Table 1).
The ~0.5 g/kg figure comes from a single study, which put the maximally effective dose for myofibrillar MPS after endurance exercise at 0.49 g·kgBM−1 (95% confidence interval 0.26–0.72), against ~ 0.24 g·kgBM−1 after resistance exercise (full text).
Table 1 also recommends a moderate (~ 10–20 g) dose of protein before and during prolonged sessions with low CHO availability, and 0.4 g·kgBM−1 of protein for athletes who cannot tolerate 1.2 g·kgBM−1·h−1 of CHO in immediate post-exercise recovery (full text, Table 1).
Adding protein increased muscle glycogen resynthesis when CHO was ingested at a suboptimal rate (~ 0.8 g·kgBM−1·h−1) but not at an adequate 1.2 g·kgBM−1·h−1, at which glycogen resynthesis plateaus (full text).
Increasing dietary protein up to 3 g·kgBM−1·day−1 in trained male cyclists better maintained endurance performance after a 4- to 7-day block of intensified training, with background CHO intakes of 6 to 8 g·kgBM−1·day−1 (full text).
In IAAO studies, the requirement was 1.83 g·kgBM−1·day−1 on a 20-km treadmill run day in endurance-trained men, and 1.71 g·kgBM−1·day−1 in female team-sport athletes in the luteal phase versus 1.40 g·kgBM−1·day−1 in males on the same protocol (full text).