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

What does an RQ of 0.7 indicate?

1. Protein being predominantly utilized

2. Only fat being metabolized

3. Balance of macronutrients

4. Pure carbohydrate utilization

The correct answer is: Only fat being metabolized

An RQ, or respiratory quotient, is a measure of the ratio of carbon dioxide produced to oxygen consumed during metabolism. An RQ of 0.7 indicates that the body is predominantly metabolizing fat for energy. In terms of metabolic processes, the RQ value can vary based on the type of substrate being used. An RQ value close to 1.0 typically indicates a higher rate of carbohydrate metabolism, as carbohydrates produce more carbon dioxide relative to the amount of oxygen consumed. An RQ of around 0.85 is indicative of a mixed substrate metabolism, where carbohydrates and fats are utilized in relatively equal proportions. In contrast, an RQ of 0.7 shows that fat is the primary fuel source, which aligns with the fact that fat metabolism produces less CO2 compared to the amount of oxygen consumed. Additionally, other macronutrient utilizations have distinct RQ values: protein metabolism typically exhibits RQ values around 0.8 to 0.9, signifying that the presence of protein use is outside the context of an RQ of 0.7. Therefore, this specific value strongly correlates with fat metabolism, affirming that a primary reliance on fats for energy is occurring at this RQ