Combined effects of carbohydrate and caffeine intake on exercise performance and metabolism

Thirteen randomized controlled trials with 128 participants indicate that the ingestion of caffeine and carbohydrates together may reduce sprint time compared to carbohydrates alone.

• Combining caffeine and carbohydrates reduced sprint time during repeated sprint protocols (SMD: -0.45; 95% CI: -0.85, -0.05).
• There was a tendency for reduced time in time trials with combined caffeine and carbohydrates, but results were less conclusive (SMD: -0.36; 95% CI: -0.77, 0.05).
• Rating of perceived exertion (RPE) was lower with combined caffeine and carbohydrates compared to carbohydrates alone during steady-state exercise (SMD: -0.43; 95% CI: -0.91, 0.05).
• Higher blood glucose levels were observed when carbohydrates were co-ingested with caffeine compared to placebo, though findings were inconsistent across studies.
• One study indicated greater fat oxidation and lower glycogen use when caffeine was added to carbohydrates.
• Increased cortisol levels were noted with the co-ingestion of caffeine and carbohydrates compared to placebo in one study.

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