This systematic review and three-level meta-analysis evaluated the effects of combining resistance training with creatine supplementation (RT + CR) compared with resistance training alone (RT) on multiple outcomes: upper- and lower-body strength, lean mass, fat mass, body-fat percentage, and total body mass. The analysis also explored whether participant characteristics (age, gender, training experience) or intervention-protocol variables (duration, weekly frequency, dosing strategy, daily dose, supplementation protocol) moderated observed effects.
The authors performed a systematic search of PubMed, Web of Science, Cochrane Library, Embase, and EBSCO from database inception through April 21, 2025, and used backward citation tracking to identify additional trials. Effect sizes were calculated as Hedge’s g and pooled using a three-level random-effects model implemented in the metafor package for R. Potential moderators were assessed via subgroup analyses and meta-regression.
A total of 63 studies were included, comprising 1,489 participants. The review synthesized trial-level data comparing outcomes in resistance training with creatine supplementation versus resistance training alone. Detailed breakdowns of individual study characteristics, dosing specifics, and participants’ baseline training status were reported across included trials but varied in completeness, which the authors note as a limitation.
Pooled findings showed that RT + CR produced statistically significant and moderate improvements in both upper- and lower-body strength compared with RT alone. Specifically, upper-body strength increased with Hedge’s g = 0.54 (p < 0.001), and lower-body strength increased with Hedge’s g = 0.55 (p < 0.001). These results indicate a clinically meaningful enhancement of strength when creatine is added to resistance training protocols in the aggregated literature.
Body composition analyses revealed a significant increase in lean mass with RT + CR (g = 0.30, p < 0.001) and a modest but statistically significant increase in total body mass (g = 0.12, p = 0.04). RT + CR was associated with a small reduction in body-fat percentage (g = −0.14, p = 0.02). No significant difference was found for absolute fat mass (g = −0.10, p = 0.14). The authors interpret the overall body-mass increase as predominantly attributable to gains in lean body mass rather than fat accumulation.
Exploratory subgroup analyses and meta-regression examined whether effects varied by participant age, sex, training experience, and by intervention-protocol variables (intervention duration, weekly frequency, dosing strategy, daily dose, supplementation protocol). The analyses suggested that age may be associated with the magnitude of strength gains: between-subgroup differences for both upper- and lower-body strength reached statistical significance, and meta-regression indicated an inverse association between age and strength effects (larger effects in studies of younger participants). The authors caution that these findings are exploratory because age subgroups were unevenly represented and multiple moderator tests were conducted.
No consistent or robust moderators were identified for body composition outcomes; intervention-protocol variables did not consistently influence pooled estimates for lean mass, fat mass, body-fat percentage, or body mass.
Across 63 trials, adding creatine to resistance training produced moderate improvements in both upper- and lower-body strength and a small-to-moderate increase in lean mass, with a modest increase in total body weight. The small reduction in body-fat percentage likely reflects increases in lean mass rather than meaningful fat loss, consistent with the nonsignificant change in absolute fat mass.
The exploratory association between younger age and larger strength effects suggests age-related variability in responsiveness to RT + CR, but this observation requires cautious interpretation because of uneven subgroup sizes and multiple comparisons.
The authors highlight heterogeneity across included trials and incomplete reporting of key contextual variables as limitations. In particular, nutritional intake and prior training background were variably and incompletely reported across trials, which constrains the ability to attribute pooled effects solely to creatine supplementation versus differences in diet, training stimulus, or participant baseline status. The exploratory moderator results (especially for age) are described as tentative.
Compared with resistance training alone, resistance training combined with creatine supplementation significantly enhanced upper- and lower-body strength and increased lean body mass in pooled trial data, without a statistically significant effect on fat mass. The modest increase in total body mass was mainly due to lean-mass gains, producing a slight reduction in body-fat percentage. Age may influence the magnitude of strength responses, but this finding should be interpreted cautiously due to uneven subgroup representation and multiple exploratory tests. Intervention-protocol variables examined did not show consistent moderation of outcomes.