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

What does an RQ less than 0.7 suggest?

1. Protein is being metabolized

2. Carbohydrate metabolism is predominant

3. Lipid metabolism

4. Balanced nutrition

The correct answer is: Lipid metabolism

An RQ, or respiratory quotient, is the ratio of carbon dioxide produced to oxygen consumed during metabolism. A value of less than 0.7 indicates a greater reliance on fat (lipid) metabolism rather than carbohydrates or protein. This is because fats yield fewer carbon atoms per molecule of oxygen consumed compared to carbohydrates, leading to a lower RQ value. In metabolic calculations, an RQ less than 0.7 typically suggests that the body is in a state of starvation or prolonged fasting, where it predominantly breaks down fat stores for energy. This metabolic state can be critical for understanding a patient’s nutritional status and energy usage, especially in clinical settings. Other options describe normal or typical metabolic processes. For instance, a balanced nutrition scenario or predominance of carbohydrate metabolism would result in RQ values closer to 1.0 or around 0.8, indicating a mix of substrates being utilized rather than a primarily lipid-based metabolism. Therefore, the indication of lipid metabolism offered by an RQ less than 0.7 is an important concept in assessing metabolic states and energy utilization.