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

When would you expect to see an RQ close to 0.7?

1. During high-fat consumption

2. During starvation or fasting states

3. In a balanced diet

4. During high-carb diets

The correct answer is: During starvation or fasting states

An RQ, or respiratory quotient, is the ratio of carbon dioxide produced to oxygen consumed during metabolism. An RQ close to 0.7 indicates a predominant use of fat for energy. This is typically observed in fasting or starvation states when the body has utilized its available carbohydrate stores (such as glycogen) and begins to rely more on fat metabolism for energy needs. In these states, the body shifts its metabolic process to break down fat and produce ketone bodies as an alternative energy source, which results in less carbon dioxide production relative to the amount of oxygen consumed, thus leading to a lower RQ value. This metabolic response contrasts with the other scenarios: During high-fat consumption or a balanced diet, the RQ may be higher due to varying contributions from carbohydrate and fat oxidation, while high-carbohydrate diets would yield an even higher RQ closer to 1.0, indicative of carbohydrate metabolism predominating. Therefore, the state of starvation or fasting is the condition where an RQ close to 0.7 is expected.