A hospitalised patient on aggressive enteral feeding undergoes indirect calorimetry. The measured respiratory quotient is 1.18. Which interpretation is correct?

• A Predominant oxidation of fat
• B Net lipogenesis from excess carbohydrate intake ✓
• C Predominant oxidation of protein
• D Calibration error, since RQ cannot exceed 1.0

Explanation

An RQ above 1.0 occurs when carbohydrate is converted to fat: lipogenesis consumes oxygen and releases carbon dioxide beyond oxidative needs, so VCO2 exceeds VO2 and the ratio rises above unity. This is seen with overfeeding, particularly excess carbohydrate calories in refeeding or TPN. Pure fat oxidation gives an RQ near 0.7, eliminating option A. An RQ above 1.0 is a real physiological finding, not an artefact, so option D is incorrect.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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