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 collision sport, including fuelling for training and match play, managing body composition without reducing athletes to arbitrary numbers, addressing recovery from muscle damage and injury, and developing practical systems around game-day nutrition.
The episode also provides insight into the realities of building a career in performance nutrition, including the importance of applied experience, interdisciplinary collaboration, and learning how to coach athletes rather than simply prescribe to them.
Timestamps:

[03:31] Interview starts
[10:26] Educating athletes on nutrition
[13:55] Breaking into elite sport
[26:26] Physiological demands of rugby
[30:53] Energy needs and timing
[38:28] Body composition measurements: utility?
[46:16] Game day fuelling strategy
[01:07:09] Key ideas (premium-only)
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James' Instagram: @morehenperformance
James' LinkedIn: Dr. James Morehen
Related episodes: #573: A Philosophy of Elite Performance Nutrition – Daniel Davey
#286: Fuelling Elite Sport – James Morton, PhD
#506: Sports Nutrition: Translating Research to Practice – Andreas Kasper, PhD

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:
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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.
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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:
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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)
 
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