American Board of Surgery Qualifying Exam (ABS QE) Practice Test

If a patient has an RQ of 0.8, how are they utilizing macronutrients?

1. They are predominantly utilizing carbohydrates

2. They are in a state of ketosis

3. They are utilizing mixed energy sources

4. They are predominantly utilizing fat

The correct answer is: They are utilizing mixed energy sources

An RQ, or respiratory quotient, of 0.8 suggests a mixed utilization of macronutrients. The RQ value is derived from the ratio of carbon dioxide produced to oxygen consumed during metabolism. When the body primarily oxidizes carbohydrates, the RQ is closer to 1.0, indicating higher CO2 production relative to O2 consumption. Conversely, a predominant fat utilization corresponds to a lower RQ, typically around 0.7, indicating the burning of fat for energy, which results in less CO2 produced compared to O2 consumed. An RQ of 0.8 indicates that the body is utilizing both carbohydrates and fats for energy, but not to a degree that would signify complete reliance on one over the other. Thus, this value reflects a mixed energy source, which is aligned with a balanced metabolism that incorporates both macro sources. This understanding is crucial, particularly when evaluating a patient's nutritional status and metabolic state in clinical settings.