Lower use of eaten sugar for energy during long exercise when the body's stored carbohydrates are low

Total carbohydrate oxidation was 84 +/- 7 g in the low-glycogen trial compared to 116 +/- 8 g in the moderate-to-high-glycogen trial during 60-120 minutes of exercise.

• Exogenous carbohydrate oxidation rates were 28% lower in the low-glycogen trial compared to the moderate-to-high-glycogen trial.
• Maximal exogenous oxidation rates were reduced from 0.88 +/- 0.04 g/min in the moderate-to-high-glycogen trial to 0.64 +/- 0.05 g/min in the low-glycogen trial.
• Increased plasma free fatty acid levels were observed in the low-glycogen trial, being 2-3 times higher than in the moderate-to-high-glycogen trial.
• Lower insulin concentrations were recorded in the low-glycogen trial compared to the moderate-to-high-glycogen trial.
• Glycogen-lowering exercise combined with carbohydrate restriction is associated with reduced oxidation rates of ingested glucose during moderate-intensity exercise.

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