Episode 5 – The Randle Cycle: A Physiology-Based Explanation of Fuel Competition and Energy Efficiency

Why do so many people feel better when they reintroduce carbohydrates — yet can’t explain why?

In this episode of Metabolic Mindset, I break down the Randle Cycle, a core concept in metabolic physiology that explains how fat, protein, and carbohydrates compete for oxidation at the cellular level. You’ll learn why high fat intake can block glucose use, why excess protein without carbohydrates can leave you exhausted, and why carbohydrates are essential for efficient energy production.

We’ll walk through the biochemistry of glucose and fatty acid oxidation, the role of pyruvate dehydrogenase (PDH), and how chronic low-carb, high-fat, or high-protein diets can push the body into a stress-adapted, inefficient metabolic state. I also explain how inadequate carbohydrate intake impacts thyroid function, cortisol, blood sugar stability, exercise performance, and overall energy availability.

This episode is not about eliminating macronutrients — it’s about restoring fuel hierarchy, metabolic efficiency, and flexibility. If you’ve ever felt tired, cold, flat in workouts, or “carb intolerant,” this episode explains what’s actually happening physiologically — and why eating carbohydrates often fixes it.

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Work with me at Nourish: https://www.usenourish.com/providers/shara-perry?referralSource=Nourish+dietitian&referralName=Shara+Perry&utm_source=Nourish_dietitian&utm_term=Shara_Perry

In this episode of Metabolic Mindset, we go beyond calories and macros and dive deep into the physiology of chronic dieting and metabolic adaptation. You’ll learn exactly how prolonged calorie restriction alters thyroid function, leptin signaling, cortisol output, mitochondrial efficiency, muscle metabolism, and fat tissue behavior — and why these adaptations make fat loss increasingly difficult over time. This episode explains, at a cellular and hormonal level, why long-term dieting backfires and what your body is actually responding to when fat loss stalls despite “doing everything right.”

Support the show

Work with me at Nourish: https://www.usenourish.com/providers/shara-perry?referralSource=Nourish+dietitian&referralName=Shara+Perry&utm_source=Nourish_dietitian&utm_term=Shara_Perry

In this episode, we break down why fat loss can stall even when calories are controlled and workouts are consistent. You’ll learn how cortisol, thyroid signaling, fuel availability, and recovery determine whether your body burns fat or holds onto it—and why eating less is often not the answer.

Support the show

Work with me at Nourish: https://www.usenourish.com/providers/shara-perry?referralSource=Nourish+dietitian&referralName=Shara+Perry&utm_source=Nourish_dietitian&utm_term=Shara_Perry