ISSA Nutritionist Practice Exam

Which method measures energy expenditure by assessing oxygen consumed and carbon dioxide produced?

1. Direct calorimetry

2. Indirect calorimetry

3. Volumetric analysis

4. Metabolic cart analysis

The correct answer is: Indirect calorimetry

Indirect calorimetry is the method that measures energy expenditure by assessing the ratio of oxygen consumed to carbon dioxide produced. This process is based on the principle that the body consumes oxygen as it metabolizes substrates for energy and produces carbon dioxide as a byproduct. By analyzing the concentrations of these gases in the air you breathe in comparison to the air you breathe out, it is possible to estimate energy expenditure and identify the type of fuel being used (carbohydrate vs. fat). Indirect calorimetry is widely used in both clinical and research settings because it is non-invasive and can provide real-time measurements of metabolic rate. This makes it a preferred choice for assessing an individual's metabolic state under various conditions, such as resting metabolic rate or during exercise. Other methods mentioned, such as direct calorimetry, measure energy expenditure by assessing heat production, while volumetric analysis focuses on the volumes of gases consumed or produced, rather than energy expenditure specifically. Metabolic cart analysis is often a term associated with the equipment used for indirect calorimetry but does not describe the method itself. Therefore, indirect calorimetry stands out as the correct and most relevant method for the question posed.