FuelBurn is a real-time metabolic substrate data field for Garmin Edge computers. Utilizing your current power output, Gross Efficiency factors, and altitude-adjusted RER scaling, it calculates your precise carbohydrate and fat combustion rates in grams per hour (g/hr). Know exactly how much you are burning and when to fuel.
Ensure your fueling strategy matches your actual metabolic demand under load.
Calculates live grams per hour of fat oxidation vs carbohydrate combustion, visualizing glycogen depletion rates as workload intensifies.
Includes an altitude correction factor (increasing baseline RER per meter gained), capturing the metabolic shift towards heavier carbohydrate dependency at elevation.
Helps you target target race carbohydrate replenishment targets (such as 60–90 g/hr) based on actual real-time consumption profiles.
Power output represents your mechanical workload, but metabolically your body is less than 25% efficient (Gross Metabolic Efficiency is typically around 21–24%). This means a mechanical work rate of 250 Watts requires approximately 1000 Watts of metabolic energy.
FuelBurn models this conversion in real-time using standard metabolic calculations. By tracking power and estimating the Respiratory Exchange Ratio (RER)—which shifts from 0.70 (100% fat oxidation) to 1.00 (100% carbohydrate combustion) as you transition from recovery to threshold—it estimates your hourly carb and fat depletion rates.
This is crucial for managing fueling during ultra-endurance events or finding your exact metabolic efficiency (FatMax) zone during base training.