In this episode, I’m joined by James Krieger, editor of REPS (Research Review for Exercise & Physique Science), to break down what the meta-analyses really say about building muscle.

We cover:

• The single most important driver of hypertrophy

• The dose–response relationship between volume and muscle growth

• Is there a cap to effective volume?

• Training to failure: necessary or overrated?

• Frequency: how often should you train a muscle?

• Stretch-mediated hypertrophy and long-length partials

• Why some volume studies appear to “disagree”

If you’re tired of social media hot takes and want to understand what the totality of evidence actually shows, this episode is for you.

James and I also discuss how we evaluate research quality and why context matters when interpreting studies, something we do every month inside the issues of REPS, where we break down the latest exercise and physique research so you don’t have to.

If you want deeper dives into the actual studies discussed in this episode (and many more), check out REPS at https://biolayne.com/reps

SPONSORS

• REPS - Research Explained in Practical Summaries: https://biolayne.com/reps

• Workout Builder – Customized training programs for all experience levels: https://biolayne.com/workout-builder

LAYNE'S COMPANIES

Carbon Diet Coach: https://joincarbon.com/podcast

Outwork Nutrition: https://outworknutrition.com

REPS Research Review: https://biolayne.com/reps

Workout Builder: https://biolayne.com/workout-builder

Team Biolayne: https://biolayne.com/online-coaching

Physique Coaching Academy: https://physiquecoachingacademy.com

FOLLOW LAYNE

http://www.facebook.com/laynenorton

http://www.twitter.com/biolayne

http://www.instagram.com/biolayne

TIMESTAMPS

0:00:00 - Intro

0:02:39 - James Background

0:04:01 - OG Message Boards

0:06:24 - Who To Listen To

0:15:01 - REPS

0:15:53 - Hypertrophy

0:26:02 - Compound vs Isolation Movements

0:33:05 - Subjective Feelings on Training

0:37:50 - Training Flexibility

0:43:22 - Training Volume

0:47:05 - Defining Sets

0:51:59 - Volume Analysis

1:02:27 - Research Challenges

1:08:12 - Workout Builder

1:09:08 - Study Discrepancies

1:16:55 - High vs Low Volume

1:22:40 - Time Constraints

1:25:15 - Volume Cycling

1:30:11 - Volume Adaptation

1:34:37 - Range of Motion

1:44:35 - What Have You Changed Your Mind On

1:59:36 - Outro

SHOW NOTES

https://biolayne.com/podcasts/dr-layne-norton-podcast

In this episode, Layne Norton, PhD, dissects the landmark 2025 systematic review & meta-analysis in Advances in Nutrition: "The Effects of Aspartame on Glucose, Insulin, and Appetite-Regulating Hormone Responses in Humans". (PMID: 40381807)

This episode is perfect if you've heard claims like "diet soda spikes insulin," "artificial sweeteners cause diabetes," or "aspartame is toxic" — Layne uses this gold-standard review to separate science from fear-mongering.

If you're into evidence-based nutrition, skeptical of viral health scares, or just want to know if your Diet Coke habit is secretly wrecking your metabolism — this episode has the receipts.

Subscribe for more deep-dive breakdowns of the latest research, and drop a comment: Do you use aspartame? Has this changed your view?

SPONSORS

• Outwork Nutrition - Evidence-Based Supplements to Support Your Hard Work: https://outworknutrition.com

• David Protein - Buy 4 cartons, get 1 FREE at: https://davidprotein.com/pages/layne

LAYNE'S COMPANIES

Carbon Diet Coach: https://joincarbon.com/podcast

Outwork Nutrition: https://outworknutrition.com

REPS Research Review: https://biolayne.com/reps

Workout Builder: https://biolayne.com/workout-builder

Team Biolayne: https://biolayne.com/online-coaching

Physique Coaching Academy: https://physiquecoachingacademy.com

FOLLOW LAYNE

http://www.facebook.com/laynenorton

http://www.twitter.com/biolayne

http://www.instagram.com/biolayne

TIMESTAMPS

0:00:00 - Intro

0:02:53 - What is Aspartame

0:05:15 - Health Claims

0:11:26 - How Aspartame is Metabolized

0:14:15 - HRCTs

0:15:56 - Outwork Nutrition

0:18:06 - Study Overview

0:19:25 - Inclusion Criteria

0:31:43 - Results

0:40:38 - David Protein

0:42:13 - Results Cont.

0:49:51 - Discussion

0:58:53 - Conclusion

SHOW NOTES

https://biolayne.com/podcasts/dr-layne-norton-podcast/study-deep-dive-does-aspartame-increase-insulin-episode-20

In this wide-ranging Q&A episode, I tackle some of the most debated topics in nutrition, training, and health — and separate what the evidence actually shows from what’s just noise.

We start with the new food guide pyramid and whether it reflects the current science, then zoom out to look at how the U.S. compares globally in calorie consumption. From there, we dig into protein intake — how much is really needed to support muscle mass and function in healthy adults, and what the best human data actually tells us.

I spend a significant portion of the episode unpacking saturated fat, cardiovascular disease, and cholesterol. We walk through randomized trials, systematic reviews, Mendelian randomization data, and mechanistic evidence to explain why LDL and apolipoprotein B matter, how dietary fats influence cardiovascular risk, and why some popular narratives around butter, seed oils, and lipid oxidation don’t hold up when you zoom out to the totality of human evidence.

I also answer practical questions on fat loss for people who feel burned out by calorie counting — what to do if tracking feels like a full-time job, where the most reliable calorie data actually comes from, and how to approach weight loss without falling into metabolic myths around insulin, glucose spikes, or arbitrary blood sugar cutoffs.

On the training side, we talk about whether the general public should prioritize strength or hypertrophy, what the data says about strength as a predictor of longevity, machines versus free weights, optimal rep ranges for muscle growth, and why different loading schemes can all work when programmed correctly.

I address common myths like creatine and hair loss, explain the biomechanics behind sumo versus conventional deadlifts (and why resetting between reps isn’t “cheating”), and share how I personally eat for health while still applying the same evidence-based principles I recommend to others.

We wrap up with genetics and obesity — how much your genes matter, whether specific variants should change how you eat, and why most people don’t need genetically tailored macro ratios to make progress.

If you’re tired of oversimplified takes, fear-based nutrition advice, and cherry-picked mechanisms, this episode is a deep dive into what the best human research actually says — and how to apply it in the real world.

SPONSORS

• Team Biolayne – One-On-One Coaching: https://biolayne.com/online-coaching

• David Protein - Buy 4 cartons, get 1 FREE at: https://davidprotein.com/pages/layne

LAYNE'S COMPANIES

Carbon Diet Coach: https://joincarbon.com/podcast

Outwork Nutrition: https://outworknutrition.com

REPS Research Review: https://biolayne.com/reps

Workout Builder: https://biolayne.com/workout-builder

Team Biolayne: https://biolayne.com/online-coaching

Physique Coaching Academy: https://physiquecoachingacademy.com

FOLLOW LAYNE

http://www.facebook.com/laynenorton