#585: Why We Think Poorly: Reason, Emotion, and Evidence-Based Reasoning

This is a Premium-exclusive episode of the podcast. To listen to the full episode you need to be subscribed to Sigma Nutrition Premium. Each year, the conversations on Sigma Nutrition Radio aim to examine the ideas that shape how we understand nutrition, health, and human behavior. This episode brings together the key insights from those discussions, revisiting the most important themes, emerging evidence, and shifts in understanding from the past year. Across topics such as dietary guidelines, ultra-processed foods, sleep, metabolism, environmental exposures, and the psychology of eating, this review distills what the science actually shows and what remains uncertain. Whether you have followed throughout the year or are tuning in for the first time, this episode provides a concise synthesis of what truly mattered and what these ideas imply for how we interpret nutrition science moving forward. Timestamps [02:23] Christopher Gardner, PhD – How dietary guidelines are shaped, misused, and what the evidence really supports. [13:10] Marie-Pierre St-Onge, PhD – The bidirectional relationship between sleep quality, circadian timing, and diet. [20:03] Duane Mellor, PhD – Rethinking ultra-processed foods: mechanisms, misconceptions, and policy realism. [29:26] Samuel Dicken, PhD – The UPDATE trial and what nutrient-matched processing tells us about satiety and intake. [35:37] Ian Mudway, PhD – Microplastics, pollution, and why evidence must outrun public fear. [43:46] Martin Caraher, PhD – The financialization of food systems and its impact on inequality and diet quality. Related Resources Go to the episode page Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course

We take a look at critical thinking in science and healthcare, examining how we often fall prey to cognitive biases, emotional reasoning, and flawed thinking. Drawing from six different experts in their respective fields, the episode explores why we sometimes believe we are being rational when in fact our conclusions aren't truly evidence-based. The discussion spans what genuine evidence-based practice means, how domain expertise matters, and how factors like identity, beliefs, and emotions can derail objective reasoning. Timestamps [02:56] Dr. David Nunan on evidence-based medicine [15:30] Dr. John Kiely on translating research into practice [26:10] Dr. Gil Carvallo on emotion and decision making [30:10] Dr. David Robert Grimes on webs of belief [37:18] Dr. Matthew Facciani identity and belief formation [42:31] Dr. Alan Flanagan on domain-specific expertise in nutrition science Related Resources Go to episode page Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course Alan Flanagan's Alinea Nutrition Education Hub

How should we think about diets that claim to optimise both human and planetary health? Can a single "reference diet" really balance the complex trade-offs between nutrition adequacy, chronic disease prevention, and environmental sustainability? These questions have gained renewed attention with the release of the 2025 update to the EAT-Lancet Planetary Health Diet. The original 2019 report proposed a mostly plant-based dietary pattern designed to improve population health while staying within planetary boundaries. But since then, new data have emerged—on nutrient requirements, disease risk, and environmental modelling—that complicate many of the original assumptions. What does the updated evidence actually say about the health impacts of eating in line with this framework? How have the environmental projections changed? And what do these evolving targets mean for individuals, policymakers, and researchers trying to translate broad sustainability goals into practical dietary guidance? These are some of the questions explored in this episode of Sigma Nutrition, which examines the 2025 EAT-Lancet update, its scientific foundations, and what it reveals about the intersection of nutrition, health, and planetary sustainability. Timestamps [01:46] Focus on the 2025 EAT-Lancet report [02:27] Overview of the Planetary Health Diet [03:13] Comparing 2019 and 2025 reports [03:40] Dietary recommendations and nutrient targets [04:14] Health and environmental impacts [09:12] Scoring methods and dietary patterns [27:00] Mortality and chronic disease outcomes [40:01] Type 2 diabetes [44:13] Neuroimaging and cognitive outcomes [49:48] Conclusions and practical implications [58:55] Key ideas segment (Premium-only) Links & Resources Go to episode page (with links to studies) Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Alan Flanagan's Alinea Nutrition Education Hub Enroll in the next cohort of our Applied Nutrition Literacy course Report: EAT-Lancet

Ultra-processed foods have become central to the way we eat and to many of the challenges we face in public health nutrition. They dominate supermarket shelves, shape population diets, and often appear as the prime suspect in rising obesity and metabolic disease rates. But beyond the label itself, what exactly makes these foods problematic? Is it their nutrient composition, their texture and palatability, the rate at which we consume them, or the broader environments that make them so accessible and appealing? The debate around ultra-processed foods sits at the intersection of metabolic science, behaviour, and policy. It raises uncomfortable questions about how food systems evolved to prioritise convenience and profit, and what it might take to meaningfully change that trajectory. In this episode, Dr. Kevin Hall joins the podcast to examine the evidence from controlled feeding studies and population research, exploring what we really know about ultra-processed foods, overeating, and how we might begin to fix the food environment. Timestamps [04:24] Dr. Hall's background and career [06:47] Ultra processed foods and health [15:10] Mechanisms behind ultra processed foods [27:00] Healthy ultra processed foods: a possibility? [30:43] Minimizing ultra processed foods in different cultures [33:03] Policy and regulation for better food quality [44:26] The importance of pilot studies in policy implementation [49:10] Future of food and sustainable diets [51:50] Key ideas segment (Premium-only) Links & Resources Go to episode page (with links to studies) Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course X: @KevinH_PhD @NutritionDanny Book: Food Intelligence: The Science of How Food Both Nourishes and Harms Us Previous episodes with Dr. Hall: #429, 376, 165, 88

This is a Premium-exclusive episode of the podcast. To listen to the full episode you need to be subscribed to Sigma Nutrition Premium. What exactly are "antioxidants," and why do they get so much hype? We often hear that blueberries, dark chocolate, and red wine are healthy because they're packed with antioxidants – but is the story really as simple as "more antioxidants = better health"? In this episode, Danny explores the true role of antioxidants in the body, challenging simplistic narratives. Are antioxidants magic molecules that single-handedly prevent aging and disease? Or is the reality more nuanced, with context and balance being key? We delve into these intriguing questions to clarify what antioxidants are, how they work, and what the current consensus tells us about using them for health. Antioxidants are frequently credited as the reason why colorful fruits and vegetables are beneficial. Yet, as past Sigma episodes on polyphenols have noted, the benefits of those plant foods aren't primarily due to direct antioxidant effects. Here we untangle common misconceptions (e.g., "antioxidants = health, always"), distinguish between different types of antioxidants, and explain why simply taking high-dose antioxidant supplements isn't a guarantee of protection – and in some cases might even backfire. By the end, health professionals and science-savvy listeners will understand the diverse roles of antioxidants, the importance of balance, and how to apply this knowledge in practice. Timestamps [01:27] Understanding antioxidants [04:19] The role of free radicals [08:43] Endogenous antioxidant systems [09:58] Dietary antioxidants [16:03] Polyphenols and their impact [24:28] Health benefits of polyphenols [27:39] Antioxidants in cognitive function [36:47] Practical takeaways on antioxidants Links & Resources: Subscribe to Sigma Nutrition Premium Go to the episode page Join the Sigma email newsletter for free Become a member of Alan Flanagan's Alinea Nutrition Education Hub Enroll in the next cohort of our Applied Nutrition Literacy course See all our other Recommended Resources Instagram: @sigmanutrition X: @NutritionDanny  

GLP-1 receptor agonists have emerged as a groundbreaking tool in obesity treatment. In this episode, Dr. Spencer Nadolsky (an obesity specialist) explains how these medications are now yielding unprecedented weight loss outcomes in people with obesity.  The discussion centers on GLP-1 agonist drugs like semaglutide and tirzepatide: how they work, how much weight loss they can produce, and why they represent a paradigm shift in obesity management.  Importantly, the conversation addresses practical aspects of using these drugs, including managing their side effects and optimizing patients' diet and lifestyle while on therapy. This topic is of great significance to nutrition science, clinical practice, and public health. Obesity is a chronic, relapsing condition that has proven difficult to treat with lifestyle changes alone. The advent of GLP-1 agonists offers new hope by inducing weight loss levels previously seen only with surgical interventions.  Understanding these medications is crucial for healthcare professionals: it enables evidence-based prescribing, proper patient counseling on diet and side effects, and integration of medication with lifestyle interventions.  Discussing safety and long-term use is vital, as millions more patients might use these drugs in coming years. From a public health perspective, GLP-1 agonists prompt debates about access and cost, given their high price and life-changing potential. Timestamps [03:25] Conversation with Dr. Spencer Nadolsky begins [05:24] Mechanism and types of GLP-1 medications [07:55] Efficacy and weight loss results [16:53] Common side effects and management [22:57] Muscle loss concerns and clinical insights [28:09] Addressing nutritional concerns with GLP-1 medications [29:38] Exploring potential benefits beyond weight loss [33:48] Marketing and misconceptions around GLP-1 [36:59] Public health and accessibility issues [43:25] Future research [46:16] Key ideas segment (Premium-only) Related Resources Go to episode page Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course Vineyard – Dr. Nadolsky's Virtual Clinic (US) Instagram: @drnadolsky @sigmanutrition Related episodes: 460: Dr. Priya Sumithran – Body Fat Regulation, Pros & Cons of Weight Loss Interventions, and GLP-1 Receptor Agonists 324: Fatima Cody Stanford, MD – Obesity Treatment & Weight Bias 395: Prof. Carel Le Roux – Current Thinking in Obesity Treatment

Public nutrition policy plays a critical role in shaping population health through laws, guidelines, and programs that influence what people eat. In this episode, Emily Callahan, an expert in nutrition policy, talks about why public nutrition policies often fall short and what "success" looks like. They discuss how evidence-based nutrition interventions can stall due to political or practical barriers, and explore examples ranging from federal food assistance programs to sodium reduction initiatives. Crucially, they address how to evaluate if a policy has worked and highlight emerging strategies (like integrating "food as medicine" into healthcare) that offer hope for better outcomes. This conversation is highly relevant for researchers, clinicians, and nutrition professionals, as it underscores the importance of policy in addressing nutrition challenges at the population level and examines how to design effective, data-driven policies for public health impact. Timestamps [05:09] Understanding public health nutrition policy [08:44] Examples of public nutrition policies [21:27] Challenges in implementing nutrition policies [31:24] Evaluating the success of nutrition policies [34:58] Sustainability and political viability of health policies [38:07] Food Is Medicine: a promising policy target [44:50] Medically tailored meals: evidence and implementation [48:55] The MAHA commission report and its implications [56:42] Future directions in nutrition policy [01:04:49] Key ideas segment (premium-only) Related Resources Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Go to episode page Enroll in the next cohort of our Applied Nutrition Literacy course JAMA Commentary: The MAHA Commission Report and Diet-Related Diseases in Youth – Mozaffarian, Callahan & Frist, 2025 Mozafarrian et al., 2024 – "Food Is Medicine" Strategies for Nutrition Security and Cardiometabolic Health Equity: JACC State-of-the-Art Review Tufts' Food Is Medicine Institute

Sodium bicarbonate is one of the most consistently supported ergogenic aids in sports nutrition research, yet its underlying mechanisms and real-world applications remain widely misunderstood. More recent developments have focused on how to optimise both the timing and formulation of supplementation. The "individualised ingestion timing" approach has emerged as a practical strategy, recognising that the time-to-peak blood bicarbonate concentration varies considerably between individuals. Similarly, novel formulations are being explored to address issues with gastrointestinal distress and practicality of dosing. These include topical approaches such as sodium bicarbonate lotion, and commercial products like Maurten's "Bicarb System." In this episode, Prof. Lewis Gough joins to discuss the latest evidence on sodium bicarbonate and performance, its mechanisms, novel delivery systems, and the key directions for future research. Dr. Lewis Gough is a Professor of Nutrition and Physiology at Birmingham City University. He is globally recognized for his research on sodium bicarbonate supplementation in sport, and his work spans applied sport and exercise nutrition, exercise metabolism, acid–base balance, and fatigue. Timestamps [03:12] Professor Gough's academic journey [06:29] Mechanisms of sodium bicarbonate and historical perspective on lactate [11:21] Sodium bicarbonate's role in performance [22:45] Individual responses to sodium bicarbonate [26:53] Timing strategies for sodium bicarbonate [32:38] Individualized approach to sodium bicarbonate timing [36:47] Traditional vs. novel delivery methods [44:27] Practical recommendations for athletes [51:18] Future research directions [01:02:08] Key Ideas segment Resources Go to episode page (w/ links to relevant studies) Subscribe to Sigma Nutrition Premium Join the Sigma email newsletter for free Enroll in the next cohort of our Applied Nutrition Literacy course See all of Sigma's "Recommended Resources"

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. Timestamps [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 Related Resources Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Become a member of Alan Flanagan's Alinea Nutrition Education Hub 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. Timestamps [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) Related Resources Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course Links to related studies (see Related Resources section)