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

Building muscle doesn’t happen in the gym alone. In Part 2 of this series, I break down the nutrition and supplementation variables that actually matter for maximizing muscle growth and which ones are overhyped or misunderstood.

We start with protein: how much you really need, why protein quality matters, the role of essential amino acids and leucine in stimulating muscle protein synthesis, and how protein distribution across the day can influence results. I also dive into how protein needs change with age, why older adults require higher per-meal and daily protein intakes, and practical recommendations to offset age-related anabolic resistance.

From there, we cover energy intake: how caloric deficits impair muscle protein synthesis, why massive surpluses don’t accelerate lean mass gains in trained lifters, and how to think about maintenance versus small surpluses depending on training status.

Finally, I break down the supplements that are actually supported by strong evidence — including creatine and whey protein: what they do, how they work, and how to use them effectively. We also cover common factors that can sabotage muscle growth, like smoking, excessive alcohol, poor sleep, and inappropriate use of NSAIDs or high-dose antioxidants.

If you want a clear, science-based framework for using nutrition and supplements to support muscle growth, without gimmicks or misinformation, then this episode is for you.

SPONSORS

• Carbon Diet Coach – 14 day free trial: https://joincarbon.com/podcast

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

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

0:05:02 - Most Important Thing

0:05:35 - Protein Structure

0:07:09 - Protein Digestion

0:09:55 - Protein RDA

0:10:40 - Nitrogen Balance

0:12:24 - Muscle Turnover

0:14:09 - Amino Acids

0:19:35 - mTOR

0:23:12 - Carbon Diet Coach

0:24:12 - How Much Protein

0:29:56 - Protein Distribution

0:39:08 - Protein and Aging

0:45:04 - Protein Quality

0:50:50 - Outwork Nutrition

0:52:17 - Calories

1:01:23 - Supplements

1:05:16 - Things to Avoid

1:13:10 - Outro

SHOW NOTES

How do muscles actually grow — and what really matters for hypertrophy?

In this episode, I break down muscle growth from the ground up, starting with muscle structure and working all the way through the practical training variables that actually drive hypertrophy.

We cover how muscle fibers are built, why muscle cells are uniquely multi-nucleated, and how satellite cells and myonuclei influence growth potential and long-term adaptations (including the concept of “muscle memory”). From there, we dig into how resistance training shifts net protein balance, why muscle protein synthesis and breakdown both rise with training, and why hypertrophy is often delayed when people first start lifting.

A major focus of this episode is mechanotransduction — how mechanical loading from resistance training is converted into chemical signals that stimulate muscle growth. We unpack what we know (and don’t know) about mTOR signaling, phosphatidic acid, kinase pathways, and why mechanical tension is the primary driver of hypertrophy.

From there, the episode gets highly practical. We break down:

• Why proximity to failure matters more than load

• How volume really works (and why “dose-dependent” doesn’t mean linear)

• The role of training frequency and how to distribute volume

• Why stretch and lengthened positions matter for growth

• Load and rep ranges for hypertrophy vs strength

• Exercise selection, machines vs free weights, and compound vs isolation lifts

• Rep tempo, intensity techniques, and what doesn’t meaningfully affect growth

• Why systemic hormone spikes from training don’t predict hypertrophy

I close with clear, evidence-based takeaways you can actually apply: how hard to train, how much volume most people need, when failure makes sense, how to structure exercises, and how to prioritize effort, recovery, and adherence over gimmicks.

If you want a science-based framework for building muscle — without myths, hype, or unnecessary complexity — this episode lays it out step by step.

SPONSORS

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

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

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

0:04:53 - Muscle Function

0:06:23 - Muscle Fibers

0:10:48...

In this Building Muscle Masterclass, I sit down with Dr. Stu Phillips — the world’s most cited researcher in exercise science and protein metabolism. If you care about building muscle, eating enough protein, lifting smarter, or cutting through the noise in the fitness world, this is a must-listen.

Stu and I go deep on the biggest questions in hypertrophy and nutrition, backed by some of the most important studies in the field:

• What actually drives muscle growth and what most people still get wrong

• How much protein you should really eat to maximize hypertrophy (and what the meta-analyses say)

• Whether high-protein diets harm your kidneys (spoiler: nope)

• Plant vs. animal protein: does the source matter, or is it all about leucine?

• Do hormone spikes from training matter for gains?

• Should women change their programming based on menstrual cycle phase?

• The truth about “lifting heavy” — do you need it for hypertrophy?

And MORE

If you want the clearest, most up-to-date breakdown of protein science and muscle growth from the guy who literally did the research I base many of my recommendations on… this is your episode.

SPONSORS

• Carbon Diet Coach – 14 day free trial: https://joincarbon.com/podcast

• 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

FOLLOW STU

https://www.instagram.com/mackinprof

http://www.twitter.com/mackinprof

TIMESTAMPS

0:00:00 - Intro

0:01:50 - Background

0:08:33 - Biochemistry First

0:12:02 - Student Experience

0:14:53 - Single Most Important Thing for Muscle Growth

0:16:04 - Mechanisms of Hypertrophy

0:19:48 - Consistency is Key

0:21:46 - Muscle Growth and Hormones

0:28:34 - Acute vs Chronic

0:32:42 - Cortisol

0:36:19 - Carbon Diet Coach

0:37:19 - Muscle, Hormones, and Training for Women

0:49:56 - Training Auto-Regulation

0:55:42 - How Much Protein

1:08:06 - Workout Builder

1:09:02 - Protein and Kidneys

1:26:20 - Muscle and Metabolic Health

1:30:05 - Cell Journal

In this week’s Q&A episode, I dig into your most common questions — from supplements to training to nutrition — and break them down with actual data, not influencer mythology. If you’ve ever wondered whether collagen is worth the hype, if fiber does more than “help you poop,” or whether turkesterone is anything more than TikTok creatine-with-a-fedora… this episode is for you.

We cover:

• Collagen:

Does it help joints? Skin? Connective tissue? Muscle? I walk through the clinical trials (including the ones influencers never mention) and explain where collagen actually works… and where it absolutely doesn’t.

• Fiber:

Yes, it helps your gut — but that’s just the start. We look at the research on mortality risk, insulin resistance, weight loss, inflammation, CKD, energy balance, colon cancer, and why higher fiber intake consistently predicts better health across multiple systems.

• Turkesterone & Ecdysteroids:

The internet loves calling this “natural anavar.” The human data… does not. I break down the preliminary studies, the animal research, and what’s real versus what’s marketing.

• Burnout & Training Balance:

How I manage training, work, and life without flaming out — and what actually matters for long-term consistency.

• Protein Needs After 40:

Do you need more protein as you age? What does the research say about anabolic resistance, amino acid signaling, and muscle protein synthesis in older lifters?

• Things That Hurt Muscle Growth:

Ice baths, alcohol, smoking, NSAIDs, corticosteroids — we go through the actual evidence on what blunts hypertrophy, what doesn’t, and what matters in the real world.

• Sugar & Weight Gain:

Do non-diabetics need to “fear” sugar? Or does it really come down to calories? We dig into metabolic ward studies, DIETFITS, high-sucrose diets, and the boring reality that calorie balance still wins.

• Men vs. Women in Training & Nutrition:

Sex differences in hypertrophy, strength gains, metabolic rate, and menstrual cycle effects on performance — what’s real and what’s bro-science?

• Training Over 50:

How many sets do you actually need to build muscle after 50? We review the dose-response data, multi-set vs single-set research, and the RCTs showing older adults can grow — there are no “non-responders.”

All research is cited directly from the studies mentioned — RCTs, meta-analyses, mechanistic papers, and long-term cohorts.

If you want evidence without the nonsense, this is your episode.

*SPONSORS*

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

• Physique Coaching Academy - Advanced Coaching and Nutrition Education for Personal Trainers: https://physiquecoachingacademy.com

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:

Ultra-processed foods (UPFs) get a lot of negative press, but are they always as bad as people think? In this episode, I sit down with researcher Samuel Dicken, who recently led a high-profile randomized controlled trial on UPFs that challenged some long-held assumptions.

We dig into what his study found, why not all UPFs are created equal, and how the way we consume them might matter more than the processing label itself. At the same time, we explore why sticking with mostly minimally processed foods is still a sound piece of nutrition advice.

If you’ve ever wondered whether “ultra-processed” automatically means “unhealthy,” or how to make sense of the latest UPF research, you won’t want to miss this conversation.

SPONSORS

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

• Carbon Diet Coach – 14 day free trial: https://joincarbon.com/podcast

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

FOLLOW SAM

https://www.instagram.com/drsamueldicken

http://www.twitter.com/SamuelDickenUK

TIMESTAMPS

0:00:00 - Intro

0:02:16 - Study Design

0:12:07 - Study Results

0:14:03 - NOVA Food Classification

0:18:53 - Research Misinterpretations

0:21:04 - Food Choices

0:24:34 - Zero Calorie Beverages

0:31:40 - Coke HFCS vs Cane Sugar

0:34:07 - David Protein

0:35:42 - Unintended Consequences

0:43:55 - LDL Cholesterol

0:47:50 - Ultra-Processed Foods Good or Bad?

0:53:11 - Are Ultra-Processed Foods Addictive?

1:02:10 - Carbon Diet Coach

1:03:10 - Nuance of Ultra-Processed Foods

1:07:35 - Negative Effects of UPFs Independent of Calories

1:13:09 - Criticism of Study Design

1:16:48 - Government Regulation

1:23:58 - Behavior Changes

1:29:37 - Animal vs Plant Based

1:33:08 - Personal Diet Habits

1:35:16 - Use Cases For UPFs

1:38:33 - The Practical Realities of Research

1:45:24 - What Have You Changed Your Mind On

1:49:14 - PhD Discussion

1:52:42 - Outro

SHOW NOTES

Creatine is SAFE, the verdict is in!

After decades of people claiming that creatine will wreck your kidneys, liver, & various other claims, a new study has put these myths to bed.

In my latest episode of the Dr. Layne Norton Podcast, I go DEEP on the most comprehensive dataset to date: a brand new meta-analysis by Kreider et al. (2025) which reviewed 250+ studies, covering over 26,000 participants, some lasting more than a decade, and examined nearly 50 potential side effects.

The verdict? Absolutely no evidence of harm.

I broke down the full paper, the methods, and what this means for athletes and everyday lifters in the latest episode of the podcast.

SPONSORS

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

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

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

0:01:33 - Meta Analysis Overview

0:02:14 - Creatine is NOT a Steroid

0:03:10 - ATP

0:05:13 - Creatine from Body and Food

0:06:05 - Creatine Non-Responders

0:06:27 - Creatine Dose

0:07:10 - Creatine Benefits

0:10:18 - Outwork Nutrition

0:11:46 - Interesting Associations

0:13:48 - Safety Questions

0:15:03 - Importance of Placebo

0:17:05 - Study Methods

0:20:05 - Study Results

0:26:08 - REPS Research Review

0:26:57 - Hair Loss

0:29:04 - Creatine is Safe and Effective

0:30:54 - Types of Creatine

0:36:54 - Creatine for Kids

0:38:50 - Recommendations

0:39:39 - Outro

SHOW NOTES

https://biolayne.com/podcasts/dr-layne-norton-podcast/study-deep-dive-creatine-is-safe-episode-13