09/08/2025
🔥 Most Important Factors for Fat Burning Capacity
1. Hormonal State (Insulin & Stress Hormones)
    •    Most powerful regulator — insulin can virtually “turn off” fat burning, while low insulin states (fasting, low-carb intake, exercise) allow it.
    •    Cortisol and adrenaline increase fat release, but insulin levels decide whether that fat actually gets oxidized or re-stored.
👉 Why it matters most: Even with high enzyme levels, if insulin is elevated, fat oxidation is minimal.
2. Mitochondrial Capacity (Energy Engines of the Cell)
    •    Mitochondria are where fat is oxidized. More mitochondria = higher ceiling for fat burning.
    •    Endurance training, zone 2 cardio, and consistent movement expand mitochondrial density.
👉 Why it’s #2: You can only burn fat as fast as your mitochondria can process it.
3. Oxygen Availability (Aerobic System Efficiency)
    •    Fat burning requires ~10% more oxygen per calorie compared to carbs.
    •    At higher exercise intensities, oxygen demand outpaces supply → body switches to carbs.
👉 Why it’s #3: Oxygen is the “fuel gatekeeper.” Without enough oxygen delivery, fat oxidation stalls.
4. Enzyme Availability (HSL, CPT-1, Beta-Oxidation Enzymes)
    •    More enzymes = better mobilization and transport of fat into mitochondria.
    •    Training, fasting, and diet all increase enzyme expression.
👉 Why it’s #4: Important, but enzymes are usually not the bottleneck unless someone is untrained or very insulin resistant.
5. Energy Demand & Caloric Balance
    •    You’ll only burn large amounts of fat if your body needs to (caloric deficit or high energy expenditure).
    •    In energy balance or surplus, fat oxidation slows because there’s no “reason” to tap into stored fat.
👉 Why it’s #5: Energy balance determines whether fat loss happens, but the factors above decide how effectivelyyou burn fat.
âś… In order of effectiveness:
1. Hormonal State → 2. Mitochondrial Capacity → 3. Oxygen Availability → 4. Enzyme Availability → 5. Energy Demand.
