#589: Causal Inference in Nutrition Science – Daniel Ibsen, PhD

This episode explores how asking better questions and using stronger methods can resolve much of the confusion in nutrition science. Dr. Daniel Ibsen discusses why nutrition research often produces conflicting results and how careful methodological thinking can clarify true diet-disease relationships. Nutrition science has unique challenges – diets are complex, people self-report their food intake imperfectly, and we can't easily run long-term diet experiments on people. Dr. Ibsen explains how embracing concepts like food substitution analysis, the "target trial" framework, and objective dietary assessment can strengthen evidence. The episode centers on methodological insights that make nutrition research more reliable and actionable. Key themes include defining dietary comparisons explicitly (the "compared to what?" question), considering people's starting diets, and using causal inference techniques to design better studies. Daniel B. Ibsen is an epidemiologist and nutritional scientist whose work bridges rigorous causal inference methods with real-world diet and cardiometabolic disease research. He is an Associate Professor at Aarhus University, Denmark. Timestamps [00:13] Introduction to the topic [03:23] Interview start [08:02] The importance of asking the right questions in nutrition science [22:18] Understanding causal inference in nutrition [28:58] Challenges and approaches in nutrition epidemiology [32:07] Mimicking dietary interventions in studies [32:55] Target trial framework [39:52] Objective vs. subjective dietary assessment [47:01] Why causal effects of ultra-processed foods cannot be identified Links/Resources: Go to the episode page (with links to mentioned studies) Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course

How much do hormonal fluctuations really influence performance and recovery? Should women be adjusting their training and nutrition based on the menstrual cycle? And do female athletes need different protein strategies or recovery protocols than men? These are questions that have fuelled countless online claims, from rigid "cycle syncing" programmes to supposedly gender-specific nutrition rules. But how much of that is actually grounded in evidence? In this episode, the conversation tackles those debates head-on, exploring what we truly know about female physiology, adaptation, and recovery, and where confident narratives outpace the science. You'll hear from four leading experts: Professors Kirsty Elliot-Sale, Stu Phillips, Shona Halson, and Dr. Eric Helms, as they unpack the data on menstrual-cycle variation, autoregulation, and the real determinants of muscle growth and recovery in women. These discussions were originally recorded live as part of "The Inside Advantage" event hosted by Optimum Nutrition at the McLaren F1 Performance Centre in the UK, where Danny Lennon moderated the session. Timestamps [02:07] Introducing the topics of discussion [07:46] Understanding the menstrual cycle [09:22] Recovery and hormonal impact [10:23] Where did "cycle syncing" claims originate? [15:01] Indirect effects of hormones on performance [17:28] Sleep and menstrual cycle [18:46] Training adaptations and hormonal differences [26:29] Do we have research on female athletes? [29:20] Muscle building: are there sex differences? [34:01] Do hormones influence training? [45:08] Key ideas segment (Premium-only) Related Resources Go to episode page (includes study links, guest bios, & more) Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Watch: Optimum Nutrition's 'Inside Advantage' event Previous episodes with these guests: #'s 452, 280, 192, 454

This episode centers on the critical gap in nutrition education within medical training and efforts to bridge it. Guest Akash Patel, a medical student who led a pilot nutrition curriculum, discusses why doctors receive little formal training in nutrition despite poor diet being a major driver of disease. With diet-related conditions (obesity, diabetes, cardiovascular disease, etc.) contributing heavily to morbidity and healthcare costs, the conversation highlights a pivotal push to better equip physicians in nutritional knowledge and counseling. Patel's work comes at a turning point: there are now calls for standardized nutrition competencies in medical education (e.g., a recent JAMA consensus) and a growing recognition that improving doctors' nutrition literacy could enhance patient care and public trust. But at the same time, medical programs already have a huge workload and little space is available for appropriate training. Others state that nutrition shouldn't fall within the remit of doctors. So how do we reconcile all this? While this episode focuses on the United States context, the concepts apply to other countries, as it outlines both the challenges and the emerging solutions for closing the nutrition training gap in medicine. Timestamps [03:21] Akash Patel's background and interests [05:22] Current state of nutrition education in medical schools [07:55] Akash's pilot program and initial findings [13:37] Challenges and considerations for curriculum integration [15:11] Effective curriculum design for nutrition education [23:38] Debating the role of nutrition education in medical training [29:00] Practical scenarios and the role of doctors [33:58] Advice for implementing nutrition education initiatives [38:15] Future directions in nutrition and medicine [43:07] Key ideas segment Links & Resources Go to episode page (with studies listed & linked) Join the Sigma email newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course Instagram: @withakashpatel @dannylennon_sigma @sigmanutrition

Never before has there been greater access to information about nutrition and health. But never before has there been such a low barrier to being seen as an "expert". There are large numbers of people getting information from, and basing their health decisions on, people who don't have direct expertise in the field in which they are talking about. Moreover, some promote the lack of domain expertise as a feature, not a bug. They claim that those that were conventionally seen as domain experts are either brainwashed, lazy in their thinking, or outright corrupt. And the solution is instead to look to those with a fresh perspective that can illuminate us on the "truth". In this episode, Alan and Danny discuss this "death of domain expertise", how it plays out online, and its ramifications for people's ability to get good information. Note: This episode was originally published as an exclusive episode for Sigma Nutrition Premium subscribers. If you wish to get more Premium-only episode or read study notes to our episodes, you can subscribe to Sigma Nutrition Premium. Timestamps [03:21] The manufactured collapse of expertise [09:58] Understanding domain specific expertise [15:10] Cross domain expertise and its limits [33:07] The illusion of learning from popular podcasts [38:26] The problem with self-proclaimed experts [46:11] The challenge of identifying true expertise [50:39] The impact of institutional distrust [56:30] Navigating the information landscape Links Go to episode page 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 Mentioned books & studies: Tom Nichols – The Death of Expertise Jonathan Haidt – The Righteous Mind Ionnidis, 2018 – The Challenge of Reforming Nutritional Epidemiologic Research

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