Libsyn Directory

#604: How To Interpret Nutrition Research – David Allison, PhD

Release Date: 05/05/2026

#610: Rock, Paper, Salmon – Errors in Interpreting Food Substitution Models

Sigma Nutrition Radio

When considering the health impact of foods, it is important to consider “compared to what?”. Increasing the amount of a certain food or nutrient in the diet, typically implies a displacement of another. While comparisons are more obvious in trials, in epidemiology food substitution models can be useful to help us determine the health effects of increasing/decreasing intake of a food, food group or nutrient. However, these models are often misinterpreted and miscommunicated as if they are a game of “rock, paper, scissors”, where one food beats another, and the losing food must be...

#609: Unprocessed Red Meat & Cancer Risk

Sigma Nutrition Radio

Unprocessed red meat and cancer risk remains one of the most debated topics in nutrition science, partly because the evidence is often presented in overly simplistic terms. The key question is not whether to adopt a vague “balanced” position on red meat, but whether the evidence clearly identifies intake levels at which colorectal cancer risk increases and whether controlled human trials support plausible mechanisms for that risk. A second issue is whether claims that fibre, vegetables, or an otherwise “healthy diet” can neutralise high red meat intake are actually supported by the...

#608: Performance Nutrition in Elite Rugby – James Morehen, PhD

Sigma Nutrition Radio

Performance nutrition in elite sport is often discussed in terms of meal plans, supplements, and macronutrient targets. However, effective practice in professional environments depends just as much on education, trust, communication, and the ability to translate scientific principles into decisions athletes can act on under real-world constraints. In this episode, Dr James Morehen discusses his work across elite rugby, football, and combat sports, with particular attention to the demands of professional rugby. The conversation explores how practitioners support athletes in a high-impact...

#607: Gut Health & Microbiome Testing: What Evidence Do We Actually Have? – Emily Leeming, PhD

Sigma Nutrition Radio

Gut health has become a major focus in nutrition, medicine, and consumer wellness, but the term is often used loosely. Claims about microbiome testing, probiotics, fermented foods, fibre, and “boosting” the gut microbiome are now common, yet the evidence behind these claims varies substantially. In this episode, Dr. Emily Leeming examines what gut health actually refers to, why it cannot be reduced to the microbiome alone, and where current microbiome science is being applied before it is ready. The discussion covers the limits of commercial stool testing, the difficulty of defining a...

PMOS (PCOS) and Diet: What Can Nutrition Realistically Do? - SNP#50

Sigma Nutrition Radio

In this episode, we examine what nutrition can realistically do in the condition historically known as PCOS, now renamed polyendocrine metabolic ovarian syndrome, or PMOS. We begin by explaining why the name change matters: the condition is not defined by ovarian cysts, but is better understood as a broader endocrine-metabolic and ovarian syndrome involving insulin resistance, androgen excess, ovulatory dysfunction, metabolic risk, and psychological burden. We then assess the nutrition evidence, including energy restriction, weight loss, carbohydrate quality, glycaemic index and load, protein...

#606: Practical Nutrition Strategies for Fat Loss – Luke Hanna

Sigma Nutrition Radio

Body composition goals, particularly bodyfat loss, are among the most common reasons people seek support from a nutritionist or health and fitness professional. While the principles are well established, the challenge is helping individuals apply them consistently in real-world conditions. Many people struggle due to hunger, unrealistic expectations, emotional eating, inconsistent routines, or overly restrictive dieting approaches. These challenges can make fat loss difficult to sustain, even when someone understands what they “should” be doing. In this episode, Luke Hanna discusses...

#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...

#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...

#603: Should Dietary Fiber Be Considered Essential? – Andrew Reynolds, PhD

Sigma Nutrition Radio

Dietary fiber is widely recognized as an important component of a healthy diet, yet it is not typically classified as an essential nutrient. In this episode, Dr. Andrew Reynolds explores whether that distinction still holds, arguing that the traditional criteria used to define essentiality may be outdated when applied to modern nutrition science. The discussion moves beyond simply acknowledging the benefits of fiber and instead examines whether it meets the foundational requirements of an essential nutrient. This includes considering its physiological roles, the body’s inability to...

#602: Avoidant/Restrictive Food Intake Disorder (ARFID) – Megan Hellner, DrPH, RD & Katherine Hill, MD

Sigma Nutrition Radio

Avoidant/Restrictive Food Intake Disorder (ARFID) is an eating disorder diagnosis characterized by a persistent restriction or avoidance of food intake that results in clinically significant consequences (medical, nutritional, and/or psychosocial), but without the weight- and shape-driven psychopathology typical of anorexia nervosa and bulimia nervosa. In this episode, Megan Hellner and Katherine Hill outline how ARFID presents across the lifespan, why it is frequently missed in routine healthcare, and what an evidence-informed assessment and treatment pathway can look like in practice. A...

More Episodes

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 that shape the field’s conclusions. The discussion moves from the philosophy of scientific inquiry to the practical realities of study design, statistical analysis, interpretation, and dissemination.

Timestamps:

[03:30] Interview start
[06:17] What is true scientific rigor?
[10:06] Study design and analysis problems in nutrition
[12:56] The DINS error
[14:14] Conflation of heterogeneity in response vs. in outcomes
[17:31] Misunderstanding of p-values and hypothesis testing
[27:01] Incorrect labelling of “responders” and “non-responders”
[34:49] Errors related to analysis of secondary outcomes
[45:01] How can nutrition science improve as a field?
[51:30] Key ideas segment (Premium-only)

Links:

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