#589: Causal Inference in Nutrition Science – Daniel Ibsen, PhD
Release Date: 12/30/2025
#605: Fasting, Nutrient Timing & CGMs: Interpreting the Evidence – Prof. James Betts
Sigma Nutrition Radio
Fasting, nutrient timing, chrono-nutrition, and continuous glucose monitoring are all topics that have generated substantial interest, but they are also areas where exaggerated claims can easily outpace the underlying evidence. In many cases, tentative hypotheses are presented as if they were already well-established conclusions, despite the fact that the research base is often more mixed and context-dependent than popular narratives imply. It is one thing for an idea to appear biologically coherent. It is another for that idea to translate into meaningful, reliable effects in real-world...
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#604: How To Interpret Nutrition Research – David Allison, PhD
Sigma Nutrition Radio
How should we decide what counts as trustworthy evidence? Scientific rigor is not a single characteristic of a study, but a chain of decisions made from the moment a question is conceived to the point at which findings are communicated to the public. Errors can occur at every stage: the question may be ill-posed, the design may be incapable of answering it, the measurements may be weak, the analysis may be inappropriate, the interpretation may overreach, and the public-facing communication may become distorted. In this episode, Dr. David Allison, PhD discusses the deeper methodological issues...
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#603: Should Dietary Fiber Be Considered Essential? – Andrew Reynolds, PhD
Sigma Nutrition Radio
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#602: Avoidant/Restrictive Food Intake Disorder (ARFID) – Megan Hellner, DrPH, RD & Katherine Hill, MD
Sigma Nutrition Radio
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#601: Gallstones & Gallbladder Conditions: Impact of Diet – Angela Madden, PhD RD
Sigma Nutrition Radio
This episode examines what we actually know (and importantly, what we do not know) about diet in relation to gallstones and gallbladder conditions. Much of the public-facing guidance around gallstones focuses on “avoiding fatty foods”, yet Dr. Angela Madden explains that this long-standing practice sits on surprisingly weak direct evidence, particularly when judged against the standards typically expected for clinical dietary recommendations. A central theme is the need to separate two distinct questions: dietary factors that influence the risk of developing gallstones (prevention), versus...
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Sigma Nutrition Radio
In this episode, Danny answers questions submitted by Premium subscribers. Questions Answered in This Episode: [00:05:13] Is eating too early (relative to chronotype) metabolically problematic? [00:16:55] Can plant-based diets reverse cardiovascular disease? [00:32:54] Are multivitamins useful insurance, or a waste with a good diet? [00:44:56] Does coevolution with foods determine human compatibility and benefit? [00:56:25] How should consumers choose supplement formulations and brands? [01:04:46] Folate vs folic acid: differences and best choice for women of...
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#600: Finite Knowledge, Infinite Ignorance
Sigma Nutrition Radio
“The more we learn about the world, and the deeper our learning, the more conscious, specific, and articulate will be our knowledge of what we do not know, our knowledge of our ignorance. For this, indeed, is the main source of our ignorance — the fact that our knowledge can be only finite, while our ignorance must necessarily be infinite.” – Karl Popper To mark Sigma Nutrition’s milestone 600th episode (and 12-year anniversary), Danny and Alan examine several areas in which their views have changed, softened, strengthened, or remained stable over the lifespan of the podcast....
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#599: Does Unprocessed Red Meat Increase Diabetes Risk? – Gil Carvalho, PhD MD & Mario Kratz, PhD
Sigma Nutrition Radio
This episode examines whether unprocessed red meat has a causal role in (1) type 2 diabetes risk and intermediate measures of glucose intolerance (insulin resistance, beta cell dysfunction, glycemic markers) and (2) cardiovascular disease (CVD) risk. While there is commonly observed risk signal from observational cohorts, there exist short-term randomized controlled trials (RCTs) that show largely null effects on glucose homeostasis. This had led to differing opinions and interpretations of the evidence base. Some feel that in the context of an otherwise healthy diet, there isn’t much to...
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#598: How Do Exercise & Diet Interact to Improve Glycaemic Control? – Jenna Gillen, PhD
Sigma Nutrition Radio
This episode examines how exercise and nutrition interact to influence glycaemic control, with particular focus on the postprandial period (i.e., the hours after eating) and on “time-efficient” exercise strategies such as low-volume interval training. Dr. Jenna Gillen outlines the physiological basis for why muscle contraction can acutely reduce post-meal glucose excursions, why repeated sessions can accumulate into longer-term improvements in insulin sensitivity, and why the nutrition context (pre- and post-exercise feeding, carbohydrate availability, and energy balance) can meaningfully...
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#597: Behavioral Psychology in Diet & Health Counselling – David Creel, PhD, RD
Sigma Nutrition Radio
In clinical practice effective nutrition, exercise, and obesity care is rarely about identifying the single “best” plan on paper. Instead, sustainable change depends on behavioral psychology: understanding the person’s context, motivation, barriers, and patterns, then co-designing practical steps that can actually be implemented in real life. David Creel PhD, RD is a clinical psychologist and registered dietitian working in weight management at the Cleveland Clinic. Dr. Creel discusses how clinicians can bridge the gap between “optimal recommendations” and what is most likely to...
info_outlineThis 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)
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- Enroll in the next cohort of our Applied Nutrition Literacy course