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 healthy microbiome, and the practical strategies most strongly supported by current evidence. Timestamps: [02:48] Interview start [04:17] Defining gut health [09:03] What is a "healthy microbiome"? [15:25] Microbiome testing - any clinical utility? [24:08] Interpreting microbiome studies [34:39] "30 plants a week" is not evidence-based [39:53] Serotonin and gut brain [45:34] Fiber research frontier Links/Resources: Go to episode page (w/ links to mentioned studies) Join the Sigma newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course Dr. Leeming's newsletter: Second Brain

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 intake, fat quality, appetite regulation, fertility outcomes, and phenotype differences. Rather than seeking a single "PCOS diet", the episode asks which dietary features may plausibly help, how strong the evidence is, and where uncertainty remains. This is a Premium-exclusive episode. To listen to the full episode, subscribe to Premium. Links: Go to episode page and resources Subscribe to Sigma Nutrition Premium Join the Sigma newsletter for free

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 practical strategies for improving body composition, including food diaries, energy-density manipulation, preloads, mindful eating, and realistic goal-setting. The discussion emphasizes identifying individual barriers, collaborating with clients, and building repeatable behaviours that support both fat loss and long-term maintenance. Luke Hanna holds a Master's degree in Obesity and Clinical Nutrition from University College London and a degree in Sport and Exercise Science from the University of Portsmouth. He currently works as a nutrition coach and personal trainer. Timestamps: [03:15] Interview [05:39] Client assessment basics [11:59] Alternatives to tracking [13:57] Volume eating [18:56] Preloads before meals [22:25] Snacking and hunger types [26:44] Habits and food environment [30:40] Managing expectations [33:51] Transition to maintenance [39:09] Key ideas (premium-only) Links: Go to episode page (with resources) Join the Sigma newsletter for free Subscribe to Sigma Nutrition Premium Instagram: @lukehannanutrition

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 interventions. In this episode, Professor James Betts discusses how to think clearly about these topics, why common errors in interpretation can lead to overstated conclusions, and what is required to properly evaluate whether an observed effect reflects a true intervention effect rather than baseline differences, inappropriate comparisons, within-group changes, or mechanistic signals being mistaken for meaningful health outcomes. Timestamps: [04:24] Background into Prof. Betts' research [07:28] Evidence in fasting research over past 5-6 years [10:15] Hype vs evidence in intermittent fasting [16:44] Spotting spin in study conclusions [17:31] Common statistical red flags [24:45] Methods matter in fasting trials [31:10] Exercise nutrient timing [38:32] CGMs what they measure, misuse and patterns [53:59] Key ideas (premium-only) Links: Go to episode page & resources (study links, bio, etc.) Join the Sigma newsletter for free Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course

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 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: Go to episode page (with list of episode resources) Subscribe to Sigma Nutrition Premium Enroll in the next cohort of our Applied Nutrition Literacy course