Which statement best describes indirect calorimetry REE measurement?

Which statement best describes indirect calorimetry REE measurement?

• A. It is less accurate than predictive equations in healthy individuals
• B. It cannot be used in patients who are fasting
• C. It closely approximates true 24-hour energy expenditure under steady state
• D. It yields the same results regardless of illness

Answer: (C)

Indirect calorimetry estimates energy expenditure by measuring oxygen consumption and carbon dioxide production and converting them to calories. When the person is in a true steady state—typically fasting, at rest, and with stable gas exchange—the resting energy expenditure measured by indirect calorimetry closely reflects the true 24-hour energy expenditure for that period, because there’s minimal influence from meals or physical activity. That’s why this method is considered a reliable way to gauge daily energy needs under controlled, steady-state conditions. It’s not less accurate than predictive equations; predictive formulas often misestimate REE, especially in patients with illness or abnormal body composition. Fasting is usually required to achieve a steady state and avoid the thermic effect of meals, so the idea that it cannot be used in fasting patients is incorrect. Illness does affect metabolic rate, so results can vary with disease state, making the statement that it yields the same results regardless of illness inaccurate.

Indirect calorimetry estimates energy expenditure by measuring oxygen consumption and carbon dioxide production and converting them to calories. When the person is in a true steady state—typically fasting, at rest, and with stable gas exchange—the resting energy expenditure measured by indirect calorimetry closely reflects the true 24-hour energy expenditure for that period, because there’s minimal influence from meals or physical activity. That’s why this method is considered a reliable way to gauge daily energy needs under controlled, steady-state conditions.

It’s not less accurate than predictive equations; predictive formulas often misestimate REE, especially in patients with illness or abnormal body composition. Fasting is usually required to achieve a steady state and avoid the thermic effect of meals, so the idea that it cannot be used in fasting patients is incorrect. Illness does affect metabolic rate, so results can vary with disease state, making the statement that it yields the same results regardless of illness inaccurate.