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June 11, 2023

Creatine and muscle-building: Help or hype?

Creatine is widely considered the most efficacious supplement for building muscle. Previous meta-analysis such as Delpino et al., Chilibeck et al, and Devries et al, have reported that creatine supplementation, when combined with resistance training (RT), substantially increases muscle mass compared to RT + placebo . The magnitude of these gains averaged ~1.1 to 1.4 kg (~2 to 3 pounds) across meta-analyses with most studies lasting 8 to 12 weeks.

On the surface, this outcome seems pretty impressive; several additional pounds of muscle gain over a few months of training is nothing to sneeze at. However, there’s a caveat to the findings: they are based on measures of fat-free mass derived from methods such as DXA, BodPod, BIA and underwater weighing.

Here’s the problem: fat-free mass comprises all non-fat tissue in the body, not just muscle. Measures of muscle mass are best obtained by direct, site-specific imaging methods such as MRI, CT and ultrasound. In support of this point, DXA (which is considered the gold-standard measure for assessing fat-free mass), does not correlate very well with direct imaging methods when assessing RT-induced changes in muscle mass (see: Tavoian et al and Delmonico et al.). The thing is, no meta-analysis had previously endeavored to determine the effects of creatine + RT on hypertrophy as assessed by direct imaging methods.

Until now…

What We Did
We searched the literature for studies that compared creatine vs placebo consumed in combination with RT on muscle hypertrophy. To be included in the analysis, studies had to involve healthy adults without musculoskeletal conditions that would impede RT performance and assess hypertrophic changes by direct imaging methods (MRI, CT, and ultrasound). We then carried out a Bayesian meta-analysis of the pooled results and subanalyzed the data based on body region (i.e., upper vs lower), age, and study duration. The study, titled The Effects of Creatine Supplementation Combined with Resistance Training on Regional Measures of Muscle Hypertrophy: A Systematic Review with Meta-Analysis, is open-access and thus free for all to read.

What We Found
When pooling the results of all studies, creatine supplementation showed a beneficial effect for hypertrophy compared to placebo. However, the magnitude of the benefit was relatively small, corresponding to an effect size of 0.11. The results showed similar improvements for the upper body and lower body musculature. Intriguingly, we found creatine elicited greater gains in younger compared to older (>55 yrs) adults.

What Do the Results Mean?
Our findings confirm that creatine is a viable muscle-building supplement when combined with RT. However, its anabolic effects were more modest than previous meta-analyses that analyzed fat-free mass as a proxy for hypertrophy.

It’s not clear why the results diverged between indirect methods of analysis (i.e. DXA, BIA, BodPod, etc) and direct imaging (i.e. MRI, CT and ultrasound), but it could be due the fact that creatine increases total body water. Conceivably, the greater FFM observed in the studies may reflect increased extracellular water accumulation (probably not a desirable outcome for most people), as intracellular fluid would be included as a component of muscle size measurements when assessed by direct imaging methods. This hypothesis warrants further investigation.

Our finding of a greater hypertrophic benefit for creatine supplementation in younger adults was unexpected and somewhat difficult to reconcile. Subanalysis by age indicated that, on average, creatine really didn’t enhance the effect of RT in older adults. It’s conceivable that older adults aren’t as willing/able to push as hard compared to their younger counterparts during training. This may diminish the effectiveness of creatine given that one of its theorized benefits is to rapidly regenerate energy stores during intense exercise, allowing you to train with higher intensity.

Note that the meta-analysis had several limitations. For one, there are a paucity of studies investigating the hypertrophic effects of creatine on women as well as resistance-trained individuals. There are some rationales lending to speculation that these populations may respond differently to creatine supplementation, but we need objective evidence on the topic. In addition, the results of our meta report average responses across groups. It is well-documented that there are responders and nonresponders to creatine supplementation. A person’s customary diet appears to be a factor in the response, with vegans showing better responses compared to meat eaters. Although our group-level data provides a good basis for predicting general responses, the only way to determine whether creatine works for you on an individual level is by experimentation.

Take-Home Conclusions
So what does this all mean from an applied standpoint?

For younger lifters seeking to maximize muscular gains, creatine seemingly is worth trying since even modest increases in muscle development would be considered practically meaningful. On the other hand, the benefits for young recreational lifters are questionable and may not be worth the monetary cost and hassle of daily consumption. Finally, older adults do not appear to achieve much of a muscle-building benefit from supplementation.

I’d note that creatine may have other beneficial effects other than muscle-building, including benefits on strength and power as well as a variety of health-related outcomes. Thus, its use should be considered based on individual goals and needs.