Body Composition & Fueling: Performance, Risk, and Why Under-Fueling Harms Athletes

Why It Matters

Athletes and coaches must balance performance gains from body-composition changes against serious physiological and performance costs of underfueling; prioritizing adequate energy intake can prevent RED-S and sustain long-term performance. Clear, evidence-based guidance and sensitive coaching are essential to avoid harm when addressing body image and nutrition.

Summary

On the Try Do podcast medical mailbag, hosts Jeff Sankoff and Juliet Hawkman with nutritionist Alex Larson examined the complex relationship between body composition, fueling, and athletic performance. They noted evidence that increases in lean mass and reductions in body fat can improve measurable performance metrics across disciplines, but cautioned that the pressure to pursue leanness often drives harmful underfueling. Larson emphasized that underfueling carries substantial health and performance risks (including Relative Energy Deficiency in Sport), while overfueling presents far fewer dangers for most athletes. The discussion also covered measurement limitations for body-fat assessment and the need for coaches to handle body-composition conversations carefully.

Original Description

In this episode of the Fast Talk Podcast by Fast Talk Labs, we dive into a critical and often misunderstood topic for endurance athletes: how body composition and fueling strategies influence performance — and the significant dangers associated with under-fueling. Drawing from a TriDoc Podcast swap episode, host Jeff Sankoff is joined by dietitian Alex Larson and coach Juliet Hochman to unpack how athletes can pursue body composition goals safely while avoiding under-fueling, low energy availability, and performance setbacks. 

🧠 In this episode, you’ll learn:

• Why fuel intake matters as much — if not more — than body composition for performance

• How chasing low body fat can lead to low energy availability and health issues like RED-S

• Why under-fueling compromises immune function, recovery, and performance

• How different body types and genetic factors influence optimal fueling and lean mass goals

• Practical strategies to adjust body composition sustainably, without jeopardizing training

• Tips for how coaches and athletes can navigate body image, performance pressure, and nutrition discussions

🎯 Whether you’re an athlete chasing performance gains or a coach guiding others, this episode helps you:

• Reframe body composition goals in a healthy, evidence-based way

• Reduce performance risk by prioritizing adequate fueling

• Understand the tradeoffs between lean mass, body fat, and energy availability

• Communicate better about nutrition, body goals, and athletic outcomes

🎙️ Featured Voices:

• Jeff Sankoff — Triathlon Coach & Emergency Physician

• Alex Larson — Sports Dietitian & Endurance Nutrition Expert

• Juliet Hochman — Endurance Coach & Performance Professional

📈 This episode bridges sports nutrition and performance psychology — helping athletes and coaches find a balanced approach to body composition, fueling, and growth without sacrificing wellness.

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