Creatine raises scale weight. That much is not controversial and has been measured repeatedly. The interesting question is what the extra kilogram or two is made of, and there the literature has a clean, documented disagreement — not between advocates and sceptics, but between two measuring instruments. This is research journalism and contains no usage guidance, per our editorial standards.
What the scale does
In a 2000 randomised, double-blind trial, 23 men with at least a year of weight training were assigned to creatine or a matched sucrose placebo across six weeks of arm-flexor strength training. The creatine group ingested 5 g four times a day for five days and 2 g a day thereafter.
| Creatine group | Placebo group | |
|---|---|---|
| Body mass | 86.7 → 88.7 kg | no change |
| Fat-free mass | 71.2 → 72.8 kg | no change |
| Fat mass, body fat % | no change | no change |
(Becque, Lochmann & Melrose, Med Sci Sports Exerc 2000;32(3):654–8, PMID 10731009)
That is the shape the whole literature repeats: about two kilograms of body mass in a matter of weeks, essentially all of it outside the fat compartment, with the placebo group flat.
Meta-analysed, the effect holds. A 2024 review of 12 randomised trials in adults under 50 found creatine added to resistance training produced +1.14 kg lean body mass (95% CI 0.69 to 1.59), -0.88 percentage points body fat and -0.73 kg fat mass, compared with resistance training alone (Desai et al., J Strength Cond Res 2024, PMID 39074168; doi:10.1519/JSC.0000000000004862).
The problem with "lean mass"
Dual-energy X-ray absorptiometry, the instrument behind most of those numbers, does not measure muscle. It sorts the body into three compartments — fat, bone mineral and lean soft tissue — and water sitting inside a muscle cell is counted in lean soft tissue, indistinguishable from the protein around it.
That matters here more than for almost any other supplement, because creatine's storage mechanism is osmotic. Filling the muscle store pulls water in with it. Six days at 20 g/day raised muscle total creatine by about 20% in the 1996 biopsy work (Hultman et al., PMID 8828669), and that filling is fast relative to any plausible rate of protein accretion.
So an absorptiometry result of +1.14 kg is consistent with 1.14 kg of new contractile tissue, with 1.14 kg of water, or with any mixture. The instrument cannot say which.
What happens when the muscle is imaged instead
A 2023 meta-analysis put exactly that question to a narrower evidence base: only trials of at least six weeks that measured hypertrophy at a specific site with MRI, CT or ultrasound — instruments that look at the tissue rather than at everything which is not fat or bone.
Across 44 outcomes from 10 studies, the pooled standardised effect of adding creatine to resistance training was 0.11, with a 95% credible interval of -0.02 to 0.25. The authors call it "a very small effect". Multivariate estimates for upper and lower body muscle thickness came to 0.10 to 0.16 cm (Burke et al., Nutrients 2023;15(9):2116, PMID 37432300; doi:10.3390/nu15092116).
| Method | What it counts | Pooled result |
|---|---|---|
| Absorptiometry (12 trials, 2024) | Fat, bone, lean soft tissue incl. water | +1.14 kg (CI 0.69–1.59) |
| Direct imaging (10 studies, 44 outcomes, 2023) | Muscle tissue at a site | 0.11 SMD (CrI −0.02 to 0.25) |
Neither meta-analysis is disreputable, the trial pools overlap, and neither result is a refutation of the other. Put side by side, though, they say something specific: if the kilogram on the absorptiometry scan were mostly contractile tissue, the imaging studies should have seen a clear thickening, and what they found was an effect whose credible interval includes zero. That is the strongest available evidence that a meaningful share of creatine's "lean mass" is not new muscle.
What the compartment studies show
The water question has been measured directly, though in small studies. A 2003 bioimpedance study of magnesium-creatine over two weeks reported body weight rising 0.75 kg and 0.4 kg in its two treatment groups, and in the chelate group intracellular water rose from 26.29 to 28.01 litres while extracellular water fell from 15.75 to 14.88 litres (Brilla et al., Metabolism 2003;52(9):1136–40, PMID 14506619).
The direction is the part worth noticing: water moved into cells and out of the space between them. That is the opposite of what a reader picturing puffiness expects, and it is why the subjective bloating complaint and the measured water shift are not the same phenomenon — a distinction we take apart on creatine and bloating.
The timescale
Two different clocks are running, and conflating them is how the "it's just water" and "it's all muscle" camps both get to sound right.
- Days. The muscle store fills — about 20% in six days at a loading rate, on biopsy. Water follows osmotically. This is the fast component of the weight change, and it happens whether or not anyone trains. Our page on the loading phase covers what those founding trials did and did not measure.
- Weeks. Resistance-training trials run 6 to 12 weeks and report the composite. Whatever tissue is added arrives on this clock, not the first one.
Most trial exposure is also larger than readers assume: across 685 trials, the mean administered amount was 0.166 g/kg/day, about 12.5 g a day, for 64.7 days (Kreider et al., 2025, PMID 40198156). We separate the three dose figures in circulation on how much creatine.
The honest summary
- Scale weight rises, by roughly 1 to 2 kg over weeks, and the effect is reproducible.
- None of it is fat. Fat mass falls slightly in the meta-analysed data and did not move at all in the 2000 trial.
- How much is muscle is unresolved, and the resolution is blocked by measurement rather than by absent studies: absorptiometry says +1.14 kg, direct imaging says 0.11 standardised units with an interval including zero.
- Water moves into cells, not around them — in the one compartment study available, intracellular water rose while extracellular water fell.
- It is reversible on the store's own timetable: muscle total creatine returned to baseline within 30 days of stopping in the 1996 study.
For the settings where added body mass is a cost rather than a goal, see creatine while cutting; for the broader grading of what creatine has been shown to do, creatine benefits by endpoint.
This page reports what has been measured and by what instrument. It contains no recommendation, and decisions about supplementation belong with a clinician.
Sources
- Desai I, Wewege MA, Jones MD, et al. The effect of creatine supplementation on resistance training-based changes to body composition. J Strength Cond Res 2024;38(10):1813–21 — PMID 39074168 · doi:10.1519/JSC.0000000000004862
- Burke R, Piñero A, Coleman M, et al. The effects of creatine supplementation combined with resistance training on regional measures of muscle hypertrophy. Nutrients 2023;15(9):2116 — PMID 37432300 · doi:10.3390/nu15092116
- Becque MD, Lochmann JD, Melrose DR. Effects of oral creatine supplementation on muscular strength and body composition. Med Sci Sports Exerc 2000;32(3):654–8 — PMID 10731009
- Brilla LR, Giroux MS, Taylor A, Knutzen KM. Magnesium-creatine supplementation effects on body water. Metabolism 2003;52(9):1136–40 — PMID 14506619
- Hultman E, Söderlund K, Timmons JA, et al. Muscle creatine loading in men. J Appl Physiol 1996;81(1):232–7 — PMID 8828669 · doi:10.1152/jappl.1996.81.1.232
- Kreider RB, Gonzalez DE, Hines K, et al. Safety of creatine supplementation. J Int Soc Sports Nutr 2025;22(sup1):2488937 — PMID 40198156 · doi:10.1080/15502783.2025.2488937
All sources retrieved 2026-09-16. Digital object identifiers verified by content negotiation on the same date.