In this episode, we explore the concept of chronotype, which reflects an individual’s biological circadian timing and how it manifests in preferred sleep–wake patterns. Understanding chronotype is important because it differs from simple diurnal preference, which may be shaped by lifestyle or psychological factors rather than biology.

We examine how chronotype is measured, from gold-standard laboratory methods to validated questionnaires used in field studies. The discussion also highlights the importance of accounting for sleep debt when estimating true biological timing. Finally, we consider the limitations of consumer devices and the practical implications of assessing chronotype in real-world settings.

• [02:02] Understanding chronotypes
• [06:26] Measuring chronotypes
• [15:12] Genetic and environmental influences on chronotypes
• [28:34] Health implications of chronotypes
• [52:21] Practical applications

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• Enroll in the next cohort of our Applied Nutrition Literacy course
• Related previous episodes: 495, 470, 469

Creatine is best known as a sports supplement for enhancing muscle strength and high-intensity performance. But could it also improve brain health and cognitive function? Or are such claims overhyped?

If creatine can support brain health, it could have implications for aging, neurodegenerative diseases, concussion recovery, and mental fatigue.

In this podcast episode, Professor Eric Rawson discusses what current science says about creatine’s effects on the brain, including memory, executive function, and protection against neurological stress.

Professor Rawson provides context on how creatine works in the body, why the brain might benefit, and what evidence exists so far.

Eric Rawson, PhD is Professor and Chair in the Department of Health, Nutrition & Exercise Science at Messiah University. For over twenty years, his research has centered on the interplay between nutrition and skeletal muscle, notably investigating how creatine supplementation affects both muscle and brain function.

• [03:14] Understanding creatine: biochemistry and history
• [07:55] Creatine supplementation and muscle performance
• [09:35] Creatine and brain health: emerging research
• [14:03] Measuring brain creatine: challenges and techniques
• [19:58] Cognitive benefits of creatine supplementation
• [26:23] Evaluating the evidence: caution and promise
• [30:45] Mega dosing and brain health protocols
• [32:04] Creatine for brain health: context matters
• [38:54] Creatine for brain injury and aging
• [51:25] Key ideas segment (Premium-only)

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• Links to related studies (see Related Resources section)

Energy expenditure is one of the most fundamental yet often misunderstood aspects of human physiology. A central question is whether there is a ceiling to how many calories we can burn, and what happens when activity levels approach that limit. Grasping these dynamics is essential for health professionals and researchers, as energy balance directly influences body weight regulation, metabolic health, and athletic performance.

Emerging research shows that our bodies regulate calorie burn not in a fixed manner, but through adaptation and compensation, revealing that the “calories in vs. calories out” model is far more dynamic than it may first appear.

In this episode, we revisit key insights from experts such as Dr. Herman Pontzer, Dr. Brent Ruby, Dr. Mark Hopkins, Dr. Eric Trexler, and Dr. Chris Melby. These perspectives cover how the body adapts to different levels of physical activity, the metabolic adjustments during weight loss (often called adaptive thermogenesis), and the concept of energy flux in weight maintenance.

Note: This episode is one of our Premium-exclusive episodes. To listen to the full episode, you’ll need to be a Premium subscriber and access the episode on the private Premium feed. Otherwise, you can hear a preview of the episode on the public feed of the podcast.

• [03:36] Contrained model of energy expendiure
• [12:33] What is the ceiling of human energy expenditure?
• [13:05] Reconciling energy intake and expenditure
• [13:32] Variability in metabolic rates
• [15:16] Adaptive thermogenesis and weight loss
• [18:37] Metabolic adaptation explained
• [31:51] Energy flux and weight maintenance

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• Go to sigmanutrition.com
• Article: The “Calories In, Calories Out” Confusion: A Comprehensive Guide to Understanding Energy Balance
• Included episodes:
  • 208 – Herman Pontzer, PhD | Constrained Energy Expenditure Model & Evolutionary Biology of Energy Balance
  • 124 – Brent Ruby, PhD | The Human Ceiling of Energy Expenditure
  • 299 – Mark Hopkins, PhD | Compensatory Eating & Activity Energy Expenditure
  • 377 – Herman Pontzer, PhD | Metabolism, Mitochondria & Measuring Energy Expenditure
  • 484 – Eric Trexler, PhD | Is Metabolic Adaptation an Illusion?
  • 318 – Chris Melby, DrPH | Impact of Energy Flux on Weight Management