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.

• [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.

• Go to episode page and resources
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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:

• Go to episode page (with resources)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Instagram: @lukehannanutrition