In this episode of Iron Culture, hosts Dr. Eric Helms and Dr. Eric Trexler are joined by Dr. Martin Refalo to discuss their recent meta-regression study on protein intake and its effects on muscle hypertrophy. They cover Martin's background, the initiation of the project, the methods used, and key findings, followed by a discussion of some critiques that have been generating discussion on social media platforms. The conversation emphasizes the importance of understanding statistical approaches in research and the implications of their findings for the fitness community. In this conversation, the Erics and Martin discuss the complexities of statistical modeling in nutrition research, the importance of parsimony, the risks of overfitting, and the challenges of controlling for covariates. The conversation also touches on the debate surrounding scaling protein recommendations by fat-free mass versus total mass, critiques of previous research on protein requirements for hypertrophy, and the ways in which these new findings support (and contradict) the authors' previously held biases. Throughout the episode, they reflect on the evolution of research in the fitness industry and the importance of engaging with critiques and feedback. Ultimately, they emphasize the need for thoughtful, contextualized, individualized application of their findings while acknowledging key limitations of their work.

Time stamps:

00:00 Introducing Dr Martin Refalo

Iron Culture Ep. 197- Training To Failure: A Comprehensive Overview

https://www.youtube.com/watch?v=oa8Z-fUuiNU

5:28 How did we get to the meta-regression and an overview of the methods

Refalo 2025 Effect of Dietary Protein on Fat-Free Mass in Energy Restricted, Resistance-Trained Individuals: An Updated Systematic Review With Meta-Regression

https://journals.lww.com/nsca-scj/fulltext/9900/effect_of_dietary_protein_on_fat_free_mass_in.179.aspx

Helms 2014 A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes

https://pubmed.ncbi.nlm.nih.gov/24092765/

20:49 The main findings

30:58 Addressing the critiques

44:08 Scaling protein recommendations to fat-free mass vs body mass and why there was no break-point analysis

Morton 2018 A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults

https://pubmed.ncbi.nlm.nih.gov/28698222/

Tagawa 2020 Dose-response relationship between protein intake and muscle mass increase: a systematic review and meta-analysis of randomized controlled trials

https://pubmed.ncbi.nlm.nih.gov/33300582/

Nunes 2022 Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults

https://pubmed.ncbi.nlm.nih.gov/35187864/

1:07:45 The practical recommendations

1:22:49 Types and the categorization of data and the secondary analyses

Murphy 2022 Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression

https://pubmed.ncbi.nlm.nih.gov/34623696/

1:39:02 Quick Q&A Software for systematic reviews and meta-analyses

1:40:45 Final thoughts on the research and closing out

Where to find Martin:

@mrfitness__