What does an RQ of 0.82 indicate?

• A. Overfeeding
• B. Underfeeding or lipid catabolism
• C. Mixed substrate utilization
• D. Lipogenesis

Answer: (B)

An RQ shows which fuels the body is burning: CO2 produced per O2 used. A value around 0.70 points to fat, around 1.00 to carbohydrate, and around 0.82 is typical for protein oxidation or a mixture with a substantial protein contribution. So an RQ of 0.82 suggests the body is deriving energy from protein (and possibly a mixed substrate), which happens in states of energy deficit when protein breakdown becomes a significant energy source. This pattern fits underfeeding or a catabolic state, where lack of calories shifts fuel use away from carbohydrate toward protein. Lipid oxidation alone would typically lower the RQ toward about 0.70, not 0.82.