Mass · CREA-MASS-01 · v2
Creatine taken alongside resistance training added more lean mass than training alone in two trials, both run in older or vulnerable adults [4][6]. But the corpus's most carefully designed trial, which deliberately separated a brief early water gain from the gains made during training, found that once training started both groups put on the same amount of lean mass [1]. The same corpus also shows that creatine raises the lean-mass figure a DXA scanner reports partly by increasing body water rather than muscle protein [9][2]. A separate year-long trial using a very low dose with no training changed nothing [5]. So the measured result points the claimed way in some trials, yet the corpus supplies its own reason to doubt how much of that is real muscle and in whom it applies.
Two randomised trials report that creatine added to resistance training produced greater lean-mass accrual than training alone: appendicular lean mass rose +1.31% with creatine plus training versus declines or near-zero change in the other arms in vulnerable older women [4], and post-exercise creatine produced a Δ3.0 ± 1.9 kg lean-tissue gain versus Δ0.5 ± 2.1 kg for placebo in older adults [6]. Against this, the trial built to remove the early water wash-in found both groups gained 2 kg of lean body mass during training with no between-group difference (p=0.71) [1]. The corpus independently documents that creatine and glycogen loading raise DXA lean-mass estimates and total body water during periods when little change in muscle protein is likely [9], with a parallel creatine-only rise in total body water and DXA lean mass in dancers doing no resistance training [2]. A one-year low-dose (1 g/d) trial without training showed no change in lean mass [5]. The contested point: The corpus divides on whether the positive DXA lean-mass gains in [4] and [6] reflect added muscle or added water, since its most confound-controlled trial was null during the training period itself [1] and two of its papers show creatine inflates DXA lean-mass readings through body water [9][2]. It also divides on reach: every positive training result sits in older or vulnerable adults, with no young resistance-trained cohort in the corpus to support the claim as a general statement.
All 9 papers behind this claim with their DOIs and what each does to it, the panel’s arbitration, the evidence gap map and the open research questions. Free, and sent to your inbox.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
The most rigorous RT-period trial [1], designed to remove the creatine water wash-in, found no between-group difference in lean body mass growth during resistance training (p=0.71), directly contradicting the positive trials [4][6].
The corpus documents that creatine inflates DXA lean-mass estimates through total body water with minimal change in muscle protein [9][2], so the positive DXA signals in [4][6] may be partly artefactual rather than true muscle accrual.
Where it remains uncertain. The wash-in-controlled trial found no between-group lean-mass difference during training (p=0.71) [1], and creatine raises DXA lean-mass estimates via total body water with little protein change [9][2].
Aleatory
Individual arms are small, with n=12 in two arms of [6], and reported standard deviations are wide (e.g. Δ3.0 ± 1.9 kg vs Δ0.5 ± 2.1 kg), so chance variation across arms is large relative to the between-group gaps.
Epistemic
Every positive training result is in older or vulnerable adults [4][6]; the corpus contains no young trained cohort to show whether the effect holds in the general population the claim implies.
Inferential
The positive outcomes [4][6] are DXA lean-mass estimates, yet [9] and [2] show creatine raises those estimates via total body water during periods when little muscle-protein change is likely, so inferring muscle accrual from the DXA signal is not secure.
The load-bearing papers from a corpus of 9, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Counter-evidence: the most rigorous RT-period analysis found creatine did not enhance LBM growth once the water wash-in was separated out.
“Following the wash-in, both groups gained 2 kg after resistance training ( p < 0.0001), with no between-group difference in lean body mass growth ( p = 0.71)”
Panel auditInternal validity: medium · scope of inference: Healthy mixed-sex adults (~31 years) over a 12-week resistance training program at 5 g/day.Key limitations: no placebo control · water-content confound on DXA · wash-in gain attributed to short-term water effect
Shows creatine raises both total body water and DXA lean-mass estimate together (without resistance training), reinforcing the water confound.
“CR demonstrated a significant increase in TBW (pre, 32.2 ± 3.5 kg; post, 32.7 ± 3.6 kg; p = 0.024) and lean mass (LM; pre, 39.8 ± 3.6 kg; post, 41.5 ± 4.5 kg; p = 0.020)”
Panel auditInternal validity: low · scope of inference: Female collegiate dancers supplementing creatine without a resistance training program.Key limitations: tiny sample · no resistance training · TBW increase confounds DXA lean mass · authors call for RT studies
Direct between-group evidence that creatine added to resistance training increases appendicular lean mass beyond training alone (older women).
“The CR+RT group (+1.31%) showed greater appendicular lean mass accrual than the PL (-1.2%), the CR (+0.3%), and the PL+RT groups (-0.2%) (p≤0.05)”
Panel auditInternal validity: high · scope of inference: Vulnerable older women over 24 weeks; outcome is appendicular lean mass, not total lean body mass.Key limitations: appendicular (not total) lean mass · narrow population of vulnerable older women · small per-group n
Null result at low dose without resistance training, bounding the claim's generality by dose and context.
“No significant changes in body weight, BMI, absolute and relative body fat, and body lean mass were observed”
Panel auditInternal validity: medium · scope of inference: Older postmenopausal osteopenic women on low-dose creatine without resistance training.Key limitations: no resistance training · low 1 g/day dose · authors note higher doses warranted
4 of 9 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
The corpus carries a directionally positive but genuinely contested signal that is undercut by its own strongest trial and its own documented water confound, so it supports only an Uncertain verdict.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Water-corrected or direct muscle measurement. The positive DXA signals [4][6] cannot be read as muscle while the corpus shows creatine inflates DXA lean mass via body water [9][2]. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A creatine-plus-resistance-training RCT measuring lean mass with a method that corrects for total body water, or a direct muscle-mass measure, alongside DXA.
Open question: Does creatine increase resistance-training lean mass once the early water wash-in is excluded? Why it is still open: The one trial designed to isolate training-period gain from wash-in found no between-group difference (p=0.71) [1], contradicting the positive DXA trials [4][6].
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 21 Oct 2026 · protocol v0.19