Adam C. Stewart
A recent meta-analysis revealed that creatine had only a “trivial to minor” effect on muscle growth. However, this language could underestimate the real effect of creatine.
If you ask most gym goers to list the supplements that actually help build muscle, you can be sure that creatine is on almost every list, and for good reason. In fact, a 2022 study found that creatine was the most popular dietary supplement among male bodybuilders. Dozens of supplements claim to help you build muscle, but very few are supported by more than one or two longitudinal studies.
Creatine has occupied a well-deserved place on the List of effective supplements since 2003, when Dr. J. David Branch published an absolute monster of a meta-analysis summarizing the previous literature on creatine. It included a total of 100 studies, 33 of which examined the impact of creatine on the measurement of lean body mass. This meta-analysis revealed that creatine had a weak (ES = 0.33) but significant effect on lean body mass.
This is essentially the situation of the country since then. There has certainly been more research on creatine supplementation, and there have even been a handful of recent meta-analyses that summarize the effects of creatine supplementation on specific outcomes or in specific populations. But Branch’s 20-year-old meta-analysis is still the article that everyone cites to support the effectiveness of creatine in increasing muscle growth.
However, attentive readers may have noticed a problem with the last paragraphs. Branch’s meta-analysis examined the effects of creatine supplementation on lean body mass, but lean body mass and muscle mass are not identical. Lean mass also contains water and creatine is known to cause a certain level of fluid retention. Thus, a skeptical reader might notice (rightly) that Branch’s meta-analysis suggests that creatine increases muscle growth (because muscle is certainly a major component of lean body mass), but it only provides indirect evidence to support this statement.
To directly evaluate the impact of creatine on muscle growth, you need studies that directly evaluate muscle growth. Instead of studies that measure lean body mass (which may only reflect changes in water retention), you will have to look for studies that measure muscle thickness or cross-sectional area.
Surprisingly, no studies have directly examined the impact of creatine on muscle growth when Branch published his meta-analysis, and there have not been many studies on the subject in recent years. However, we now have enough studies on the subject to justify a meta-analysis that Burke and his colleagues completed earlier this year.
The researchers identified all the studies that met these criteria:
The studies were necessary to compare resistance training without creatine to resistance training with additional creatine. In addition, the resistance training intervention had to last at least six weeks.
The studies had to be carried out on healthy mature subjects.
The studies had to be published in peer-reviewed journals in English.
The studies were necessary to directly assess muscle size before and after exercise using methods such as ultrasound, computed tomography (CT) or magnetic resonance imaging (MRI).
The studies were not able to provide the subjects with additional potentially anabolic ingredients (that is, they had to test the effects of creatine in isolation, and not as part of a multi-ingredient supplement).
In the end, 11 studies met these inclusion criteria and were included in the meta-analysis.
Just to skip to the main discovery: Creatine supplementation generally increased muscle growth, but the size of the grouped effect was (apparently) tiny: ES = 0.11. you would generally classify this as a “trivial” effect.
