Study analysis · Nutrients · 2023
Creatine doesn't make your muscles bigger—for most people.
Taking creatine with weights makes muscles slightly thicker, but so slightly that almost no one can see or feel the difference.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study looked at lots of experiments where people took creatine or a fake pill while lifting weights, and measured their muscles with special scans. It found that creatine might help muscles grow just a tiny bit more than not taking it—but it’s not a huge difference. We can’t say for sure it always works, but it’s the best kind of evidence we have.
What’s the bottom line?
This study looked at whether taking creatine pills while lifting weights helps muscles grow bigger, using scans to measure real muscle changes, not just weight gain.
How strong is this study?
This study is pretty well done because it checked many good experiments, used fancy math to combine them fairly, and avoided fake measurements by using real muscle scans. But some of the original studies didn’t tell us if people knew if they were taking creatine or not, so we have to be a little careful trusting every detail.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
0 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control groupno control group
- Sample sizeno sample size reported
- Follow-upno follow-up reported
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 553 / 100
Probability of being correct
The highest quality evidence. Systematic reviews and meta-analyses that pool randomized controlled trials, giving the most reliable summary of experimental evidence.
This design can establish causation. This study is a systematic review and meta-analysis of RCTs, which can establish causation because the included studies used randomization to assign participants to creatine or placebo groups. However, the overall effect size is very small and confidence intervals include zero for some analyses, meaning the causal effect, while statistically probable, is not large or consistently strong across all subgroups.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding disclosures were reported in the text; study appears independently conducted.
Independent Analysis Safeguards
- Preregistration on Open Science Framework
- Use of multiple independent coders for data extraction with ≥90% agreement threshold
- Third reviewer resolved discrepancies
- Blinded data extraction by two authors
- Bayesian analysis with default weakly informative priors to reduce bias
- Use of PRISMA guidelines for systematic review
- Methodological quality assessed using Downs and Black tool with three independent reviewers
No conflict of interest section, funding statement, or industry affiliations were disclosed. All authors' affiliations are academic and no industry ties are mentioned. The study's methodological rigor, including preregistration, independent coding, and Bayesian analysis, reduces risk of bias.
Key takeaways
- 01
Muscles got slightly bigger—about 0.1 to 0.16 cm thicker—with creatine, but only in a few people.
- 02
About 1 in 4 people didn’t respond at all.
- 03
The muscle growth is so tiny it’s unlikely to be noticeable or meaningful for most people trying to build muscle.
Surprising findings
- Creatine’s effect on muscle growth is smaller than previously thought—especially when measured directly, not via lean mass estimates.Most meta-analyses claimed creatine adds 1–1.4 kg of lean mass, but those included water weight. This study isolates muscle tissue and finds near-negligible growth.
- There’s no meaningful difference in muscle growth between upper and lower body—contrary to some prior lean mass studies.Earlier research suggested creatine boosted upper body more. This study shows the effect is uniform across limbs, debunking regional myths.
Practical takeaways
If you’re spending money on creatine, track your progress with photos and measurements for 8 weeks—if you don’t see or feel any change, you might be a nonresponder.
Nonresponse is common (20–30%), and this study didn’t test women or trained lifters enough to generalize.
medium confidenceConsider creatine for performance (e.g., more reps, faster recovery) rather than muscle size—its real benefit is in training intensity, not hypertrophy.
The study didn’t measure strength gains, only muscle thickness—so don’t assume it won’t help your lifts.
high confidenceWhy this study matters
1 in 4 People Get Zero Benefit
20–30% of people are 'nonresponders' to creatine—meaning their muscles don't grow at all, even with consistent training. This is likely due to already high baseline creatine levels or low type II muscle fiber content.
Most people think creatine works for everyone—it’s marketed as a universal muscle builder. This shows it’s actually a genetic lottery, which changes how you should approach supplements.
Muscles Grew… But Only by a Paperclip
Muscle thickness increased by just 0.10–0.16 cm across all muscle groups—about the width of a paperclip. The standardized effect size was 0.11, which is considered 'very small' in exercise science.
People spend hundreds on creatine expecting dramatic gains. This shows the actual physical change is so tiny it’s invisible without medical imaging.
Younger People Benefit Slightly More
Young adults (avg. age 23.5) saw a small advantage (standardized difference 0.17) over older adults (avg. age 61.6), but the confidence interval was wide (−0.45 to 0.09), making the difference statistically uncertain.
It challenges the idea that creatine is equally effective for all ages—suggesting biology matters more than dosage, which could shift marketing toward younger demographics.
It’s Not Water Retention—It’s Real (But Tiny) Muscle
Unlike past studies that measured total lean mass (which includes water), this one used MRI, CT, and ultrasound to isolate actual muscle tissue—confirming the gain is real, not just fluid.
People blame creatine bloat for looking 'puffy.' This proves the tiny growth is real muscle, not water—so the supplement isn’t lying, it’s just underwhelming.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
This study looked at whether taking creatine pills while lifting weights helps muscles grow bigger, using scans to measure real muscle changes, not just weight gain.
Research results
Muscles got slightly bigger—about 0.1 to 0.16 cm thicker—with creatine, but only in a few people. About 1 in 4 people didn’t respond at all.
What this means - more context
The muscle growth is so tiny it’s unlikely to be noticeable or meaningful for most people trying to build muscle.
This study assesses whether creatine supplementation combined with resistance training enhances regional muscle hypertrophy using direct imaging measures.
A meta-analysis of 10 RCTs found creatine supplementation combined with resistance training produces a very small increase in muscle hypertrophy (standardized effect size 0.11, 95% CrI: −0.02 to 0.25), with minor increases in muscle thickness (0.10–0.16 cm) in upper and lower body, but no practical significance for most individuals.
Methods Used
Systematic review and Bayesian meta-analysis of 10 randomized controlled trials (n=44 outcomes) using MRI, CT, or ultrasound to measure regional muscle hypertrophy in healthy adults over ≥6 weeks; multivariate and subgroup analyses assessed age, body region, and study duration effects.
Main Finding
Creatine supplementation combined with resistance training results in a very small increase in muscle hypertrophy (pooled standardized effect size: 0.11, 95% CrI: −0.02 to 0.25), with small absolute increases in muscle thickness (0.10–0.16 cm) across muscle groups; effect is likely not due to water retention but is limited by high interindividual variability and nonresponse in 20–30% of users.
Confidence Level
Moderate; based on a pre-registered systematic review with Bayesian meta-analysis of 10 RCTs using direct imaging, but limited by high heterogeneity, small sample sizes in subgroups, and lack of female-only studies.
Study Flags
Red Flags
- •High interindividual variability with 20–30% nonresponders
- •Limited data on female participants and resistance-trained individuals
- •Small effect sizes with wide confidence intervals suggesting low practical significance
Surprising Findings
Creatine’s effect on muscle growth is smaller than previously thought—especially when measured directly, not via lean mass estimates.
Most meta-analyses claimed creatine adds 1–1.4 kg of lean mass, but those included water weight. This study isolates muscle tissue and finds near-negligible growth.
Practical Takeaways
If you’re spending money on creatine, track your progress with photos and measurements for 8 weeks—if you don’t see or feel any change, you might be a nonresponder.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 553 / 100
Probability of being correct
The highest quality evidence. Systematic reviews and meta-analyses that pool randomized controlled trials, giving the most reliable summary of experimental evidence.
Human Meta-Analysis
Subject
Moderate probability
on the GRADE evidence scale
This study looked at lots of experiments where people took creatine or a fake pill while lifting weights, and measured their muscles with special scans. It found that creatine might help muscles grow just a tiny bit more than not taking it—but it’s not a huge difference. We can’t say for sure it always works, but it’s the best kind of evidence we have.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Used direct imaging (MRI, CT, ultrasound) to measure muscle hypertrophy, avoiding confounding by water retention
- Preregistered protocol and followed PRISMA guidelines
- Included only studies with ≥6 weeks duration, reducing short-term noise
Weaknesses
- Heterogeneity in training protocols, creatine dosing, and participant characteristics across studies
- Limited data on women and resistance-trained individuals
- Use of default weak priors due to lack of prior data, reducing precision
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
This study looked at whether taking creatine pills while lifting weights helps muscles grow bigger, using scans to measure real muscle changes, not just weight gain.
Research results
Muscles got slightly bigger—about 0.1 to 0.16 cm thicker—with creatine, but only in a few people. About 1 in 4 people didn’t respond at all.
What this means - more context
The muscle growth is so tiny it’s unlikely to be noticeable or meaningful for most people trying to build muscle.
This study assesses whether creatine supplementation combined with resistance training enhances regional muscle hypertrophy using direct imaging measures.
A meta-analysis of 10 RCTs found creatine supplementation combined with resistance training produces a very small increase in muscle hypertrophy (standardized effect size 0.11, 95% CrI: −0.02 to 0.25), with minor increases in muscle thickness (0.10–0.16 cm) in upper and lower body, but no practical significance for most individuals.
Methods Used
Systematic review and Bayesian meta-analysis of 10 randomized controlled trials (n=44 outcomes) using MRI, CT, or ultrasound to measure regional muscle hypertrophy in healthy adults over ≥6 weeks; multivariate and subgroup analyses assessed age, body region, and study duration effects.
Main Finding
Creatine supplementation combined with resistance training results in a very small increase in muscle hypertrophy (pooled standardized effect size: 0.11, 95% CrI: −0.02 to 0.25), with small absolute increases in muscle thickness (0.10–0.16 cm) across muscle groups; effect is likely not due to water retention but is limited by high interindividual variability and nonresponse in 20–30% of users.
Confidence Level
Moderate; based on a pre-registered systematic review with Bayesian meta-analysis of 10 RCTs using direct imaging, but limited by high heterogeneity, small sample sizes in subgroups, and lack of female-only studies.
Study Flags
Red Flags
- •High interindividual variability with 20–30% nonresponders
- •Limited data on female participants and resistance-trained individuals
- •Small effect sizes with wide confidence intervals suggesting low practical significance
Surprising Findings
Creatine’s effect on muscle growth is smaller than previously thought—especially when measured directly, not via lean mass estimates.
Most meta-analyses claimed creatine adds 1–1.4 kg of lean mass, but those included water weight. This study isolates muscle tissue and finds near-negligible growth.
Practical Takeaways
If you’re spending money on creatine, track your progress with photos and measurements for 8 weeks—if you don’t see or feel any change, you might be a nonresponder.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 553 / 100
Probability of being correct
The highest quality evidence. Systematic reviews and meta-analyses that pool randomized controlled trials, giving the most reliable summary of experimental evidence.
Human Meta-Analysis
Subject
Moderate probability
on the GRADE evidence scale
This study looked at lots of experiments where people took creatine or a fake pill while lifting weights, and measured their muscles with special scans. It found that creatine might help muscles grow just a tiny bit more than not taking it—but it’s not a huge difference. We can’t say for sure it always works, but it’s the best kind of evidence we have.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Used direct imaging (MRI, CT, ultrasound) to measure muscle hypertrophy, avoiding confounding by water retention
- Preregistered protocol and followed PRISMA guidelines
- Included only studies with ≥6 weeks duration, reducing short-term noise
Weaknesses
- Heterogeneity in training protocols, creatine dosing, and participant characteristics across studies
- Limited data on women and resistance-trained individuals
- Use of default weak priors due to lack of prior data, reducing precision
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
This study is pretty well done because it checked many good experiments, used fancy math to combine them fairly, and avoided fake measurements by using real muscle scans. But some of the original studies didn’t tell us if people knew if they were taking creatine or not, so we have to be a little careful trusting every detail.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
0 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control groupno control group
- Sample sizeno sample size reported
- Follow-upno follow-up reported
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 553 / 100
Probability of being correct
The highest quality evidence. Systematic reviews and meta-analyses that pool randomized controlled trials, giving the most reliable summary of experimental evidence.
This design can establish causation. This study is a systematic review and meta-analysis of RCTs, which can establish causation because the included studies used randomization to assign participants to creatine or placebo groups. However, the overall effect size is very small and confidence intervals include zero for some analyses, meaning the causal effect, while statistically probable, is not large or consistently strong across all subgroups.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding disclosures were reported in the text; study appears independently conducted.
Independent Analysis Safeguards
- Preregistration on Open Science Framework
- Use of multiple independent coders for data extraction with ≥90% agreement threshold
- Third reviewer resolved discrepancies
- Blinded data extraction by two authors
- Bayesian analysis with default weakly informative priors to reduce bias
- Use of PRISMA guidelines for systematic review
- Methodological quality assessed using Downs and Black tool with three independent reviewers
No conflict of interest section, funding statement, or industry affiliations were disclosed. All authors' affiliations are academic and no industry ties are mentioned. The study's methodological rigor, including preregistration, independent coding, and Bayesian analysis, reduces risk of bias.
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
11 researchersIf this is your work, this is how we attribute it on Fit Body Science. Ryan Burke is listed as the lead author.