Sigma Nutrition Radio

Can an athlete reduce the environmental impact of their diet while still meeting the demands of training, competition and recovery? Peter Res argues that these aims can be compatible, provided dietary changes are planned around the athlete's needs.

The discussion looks at practical changes athletes can make to make their diets more environmentally sustainable. This includes tips on increasing the contribution of plant proteins, maintaining adequate energy intake, and making plant-rich eating practical within sporting environments.

• [04:21] Peter Res' background

• [05:22] Defining sustainability metrics

• [08:17] Biggest diet change to make it more environmentally sustainable

• [09:23] Is local and organic actually better?

• [13:44] Athlete fears about protein

• [18:07] Barriers for athletes

• [19:37] Fueling high calorie needs

• [21:26] Micronutrients

• [24:02] Performance effects

• [26:32] Athletes as role models

• [30:17] Easy first steps

• [34:21] Premium-only: key ideas segment

Links:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• LinkedIn: Peter Res
• Fork Ranger
• Related episodes:
  • #320: Hannah Ritchie, PhD – Environmental Impacts of our Diet: Climate, Carbon Footprint & Land Use
  • #446: How Climate Change Impacts Nutrient Status
  • #584: EAT-Lancet: Does the Planetary Health Diet Improve Human Health?

Men commonly feel that if their testosteone isn't "optimized" and high, they are missing out on greater health in a variety of ways. But what can a testosterone result actually tell us? How can results be interpreted with appropriate nuance that is needed? How low is low enough to be problematic?

In situations where a test flags testosterone as low, there is a belief this means automatically starting testosterone replacement therapy. While TRT can be an excellent intervention in appropriate cases, when is it actually likely to benefit someone, and when is it not?

For many people the decision seems straightforward: get a blood test, see whether testosterone is a little low, and start TRT. However, this simplistic thinking is full of potential issues that are important to understand.

Dr. Austin Baraki returns to discuss how testosterone testing should inform treatment decisions, what benefits to expect, and the questions surrounding fertility and long-term safety.

• [03:50] Dr Austin Baraki's work

• [06:33] When and why test?

• [10:36] Probability and context impacts interpretation

• [14:13] What labs measure

• [21:15] Specific vs nonspecific symptoms

• [28:35] Primary vs secondary hypogonadism

• [32:30] Lifestyle vs TRT decisions

• [35:21] TRT risks

• [39:32] Testing timing and variability

• [41:55] Androgen receptor genetics

• [44:28] Free vs total testosterone

• [48:57] Low-normal results: what now?

• [57:45] TRT risks?: heart and prostate

• [01:03:55] Side effects and monitoring

Links:

• Go to episode page & resources
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Instagram: @austin_barbellmedicine
• Barbell Medicine
• McCormack & Holmes, 2020 – Your results may vary: the imprecision of medical measurements
• #417: Austin Baraki, MD – What Do Nutrient Blood Tests Actually Tell Us?: Understanding Biomarkers
• #334: Austin Baraki, MD – Potential Harms of Screening, Overdiagnosis and Overtreatment

Body composition testing is widely used in research, sport and clinical practice. But what are these methods actually measuring, and how much confidence should we place in the numbers they produce?

In this episode, we examine the assumptions behind common approaches including DXA, bioelectrical impedance, and skinfold measurements. We discuss the distinction between accuracy and reliability, the value and limitations of repeated measurements, and how coaches, clinicians, researchers and individuals can select an appropriate method and interpret the data without overstating its precision.

Joining Danny to discuss these issues is Professor Grant Tinsley, Professor of Human Performance at Texas Tech University and Director of its Energy Balance and Body Composition Laboratory.

• [03:04] Grant Tinsley's research

• [05:25] What body composition means

• [08:50] Skeletal muscle mass vs. fat-free mass vs. lean soft tissue

• [11:51] How different methods estimate body composition

• [23:38] Group vs individual accuracy

• [31:09] Standardizing testing conditions and assessments

• [36:36] Reliability testing thresholds

• [40:08] Understanding phase angle in bioelectrical impedence results

• [45:02] Consumer devices

• [50:55] Not all benefit from monitoring

• [54:14] Using data wisely

• [01:02:55] Key Ideas (premium-only)

Links/Resources:

• Go to episode page (references, bio, study notes)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course

Why do some foods feel difficult to stop eating, while others can be highly enjoyable without prompting the same tendency to overconsume? Answering this requires a clearer understanding of food reward, including the distinction between liking a food, wanting it, and perceiving it as easy to overeat.

In this episode, we examine how nutritional composition, sensory characteristics, learned beliefs and the eating context may shape hedonic overeating. It also considers the limits of using broad food categories to explain complex eating behaviour.

Discussing all this is Professor Graham Finlayson, professor of Psychobiology at the University of Leeds, whose research focuses on human appetite, food reward and the psychological processes involved in eating behaviour and weight control.

• [04:02] Prof. Finlayson's research
• [06:06] Food reward
• [07:13] Liking versus wanting
• [12:43] Measuring wanting in research
• [15:27] Does wanting predict overeating?
• [16:36] Study on hedonic overeating
• [23:19] Perception and context effects
• [26:24] Does ultra processing classification add anything?
• [36:09] Key takeaways and future work
• [40:35] Premium key ideas

• Go to episode page
• Subscribe to Sigma Nutrition Premium
• Join the Sigma newsletter for free
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Study: Finlayson et al., 2025 – Food-level predictors of self-reported liking and hedonic overeating: Putting ultra-processed foods in context

Commonly people are talking about "peptides" to refer to a heterogeneous group of peptide medications or investigational compounds. These are increasingly promoted for injury recovery, tissue repair, performance and longevity, with BPC-157 attracting particular attention.

But what evidence supports the claims made about these compounds? How should animal studies, biological mechanisms and personal anecdotes be interpreted? What is currently known about their safety? And what do recent regulatory discussions actually mean for their medical status and availability?

In this episode, physician and Barbell Medicine founder Dr. Jordan Feigenbaum examines the evidence surrounding BPC-157 and other peptide medications, alongside the wider questions of risk, access and informed decision-making.

• [00:13] What we want to address

• [04:47] Interview start

• [05:29] What do we mean by "peptides"?

• [10:32] BPC-157 evidence

• [16:49] Sourcing of peptides

• [20:19] The gray zone of pro-peptide communication

• [24:16] Risk sourcing vs drug effects

• [26:25] FDA lists and compounding

• [31:05] Risk tolerance and informed consent

• [43:02] Why did pharma abandon peptide research?

• [47:44] Harm reduction debate

• [51:48] Practical takeaways

• [56:20] Key Ideas segment (Premium members only)

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Barbell Medicine
• Instagram: jordan_barbellmedicine
• Book: Signal: What Testosterone Levels Are Telling You About Your Health
• Related episode: #524: Strength & Fitness Levels for Reducing Chronic Disease Risk & Promoting Health Ageing – Jordan Feigenbaum, MD
• Further reading:
  • Emerging use of BPC-157 in orthopaedic sports medicine: a systematic review. 2025.
  • Ruenzi M, Stolte M, Veljaca M, et al. Efficacy and safety of PL 14736 (BPC 157) in patients with active ulcerative colitis. Gastroenterology. 2005. Meeting abstract; full study not published.

Most dietary guidelines recommend eating one to two servings of fish per week, often specifying that at least one serving should be oily fish. But how directly is that recommendation supported by evidence? And does adding fish to the diet improve outcomes?

This episode examines where current fish-intake recommendations originated, why findings may appear contradictory, and what substitution analyses can tell us about replacing fish with alternative options.

It also considers evidence from pescatarian and vegetarian cohorts, including whether adding fish would improve an already high-quality diet and whether removing it from a plant-forward diet is likely to provide further benefit.

• [00:20] Setting out the question at hand

• [03:26] Overview of typical fish intake recommendations

• [07:10] Is there good evidence for suggested intakes?

• [08:10] Historical context

• [13:22] Key evidence: DART trial and cohort data

• [19:27] Analysis from Mohan et al.

• [25:04] Comparator issue: what is fish replacing?

• [30:52] Fish protein vs. plant protein

• [44:29] Vegetarian vs. pescatarian cohorts

• [55:20] Conclusions

• [01:00:50] Key Ideas segment (Premium-only)

• Go to episode page (with full study reference list)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Subscribe to Alan's Alinea Nutrition Education Hub
• Enroll in the next cohort of our Applied Nutrition Literacy course

Wellness and optimisation culture increasingly presents itself as "science-based". But citing studies, using technical language, or having scientific credentials does not guarantee that the underlying evidence is being represented accurately.

In this episode, exercise science researcher Dr. Nick Tiller, discusses how science can be selectively packaged, overstated, and used to support commercially attractive health claims. It explores the difference between science communication and science commodification, why scientific scepticism is distinct from cynicism, how anecdotes and mechanistic explanations can mislead, and why a single peer-reviewed study should never be treated as definitive evidence.

The conversation also looks further upstream at problems within science itself, including low statistical power, p-hacking, publication bias, questionable research practices, and academic incentives that may favour novelty and positive findings. These issues can then be amplified through media, social platforms, and the wellness industry until tentative findings become confident recommendations.

• [03:14] Interview start

• [06:22] The health and wellness "lie"

• [08:38] Optimization and the illusion of control

• [11:14] Science communicators vs commodifiers

• [14:21] Vitamin D hype case study

• [20:54] Spotting misinformation online

• [24:50] Skepticism not cynicism

• [28:47] Guidelines for debunking

• [33:46] Spotting the grift pattern

• [41:25] Bad science in academia

• [54:47] Key ideas segment (Premium-only)

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Dr. Tiller's website
• Tiller & Phillips, 2023 – How Skepticism (not Cynicism) Can Raise Scientific Standards and Reform the Health and Wellness Industry
• Tiller et al., 2024 – The Nontechnical Summary: A New Initiative to Enhance the Translation of Sports Science Research and Reduce the Spread of Misinformation

Effective athlete support requires more than delivering technically correct nutrition advice. It depends on understanding the athlete's wider environment, anticipating the pressures that disrupt good intentions, and building flexible routines that remain useful across training, competition, travel and everyday life.

This episode explores how practitioners can move beyond rigid prescriptions, use "good, better, best" options, measure meaningful progress, and create environments in which athletes can communicate openly about difficulties. It also examines identity, transitions out of sport, and why sustainable support should develop an athlete's autonomy rather than dependence on the practitioner.

To discuss all this is Gemma McGuinness, registered performance nutritionist, former professional footballer and co-founder of Verus Performance.

• [02:38] Interview start

• [03:48] Nutrition beyond performance

• [10:10] Identity and food choices

• [18:47] Standards versus perfectionism

• [24:52] Planning that actually works

• [28:32] Measuring progress in athletes

• [33:37] Where discipline can cause problems

• [38:40] Building high performance environments

• [45:37] Key ideas (Premium-only)

Links:

• Go to episode page
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Instagram: @gemmcguinnness
• Verus Performance
• Davey Nutrition
• Gemma's Substack

This episode answers one of the questions raised in the most recent Q&A episode on Sigma Nutrition Premium.

The full episode includes the following questions:

1. Fiber: Independent effect or proxy for healthy foods?
2. Exposure frequency for matched dose of red meat
3. MTHFR gene mutations and 5-MTHF
4. Typical fish oil supplements vs pharmaceutical-grade products
5. Health impacts of saturated fat in coconut products
6. Do I need to consume whole grains?
7. Could the increasing use of AI pose a threat to doing rigorous science?

To listen to the entire episode (plus the back catalogue of all Premium-exclusive episodes) become a member of Sigma Nutrition Premium.

For episode info and mentioned research go to the episode page here.

Medical screening is often framed as an uncomplicated good: if disease is found earlier, treatment can begin earlier and outcomes should improve.

This episode examines why that reasoning is incomplete. Screening can produce benefit, but it can also generate false positives, incidental findings, overdiagnosis, overtreatment and diagnostic cascades.

Dr. Austin Baraki discusses the distinction between screening people without relevant symptoms and investigating a clinical problem, the probabilistic interpretation of test results, biases that can make screening appear more effective than it is, and the importance of shared decision-making before a test is ordered.

• [03:35] What screening means
• [06:36] Choosing what to screen
• [11:59] Sensitivity and specificity
• [16:54] Predictive value and prevalence
• [22:16] Harms of screening and testing
• [31:02] Overdiagnosis and biases
• [41:40] The $50,000 physical
• [44:49] Overdiagnosis vs false positives
• [53:03] Overtreatment and surveillance
• [57:22] Clinician action bias
• [01:02:30] What to screen for

Links:

• Go to episode page (with resources)
• Join the Sigma newsletter for free
• Subscribe to Sigma Nutrition Premium
• Enroll in the next cohort of our Applied Nutrition Literacy course
• Instagram: @austin_barbellmedicine
• Twitter: @AustinBaraki