Indirect Calorimetry:

There is no perfect way to measure mitochondrial health, but if there were a best choice available it would be indirect calorimetry. Indirect calorimetry is a method that measures the respiratory gases oxygen and carbon dioxide to determine what someone’s metabolic rate is. More simply it measures resting metabolic rate (RMR) or resting energy expenditure (REE), which determines the number of calories needed by a person to live. RMR and REE can be used interchangeably. By analyzing these parameters of breath analysis and knowing the level of activity a person has during the day, you could tailor a diet specifically for that person. If you wanted someone to maintain their weight you would want to know the calories needed to perform their physical activity and the calories needed for their resting metabolic rate to equal the number of calories consumed. RMR is in large measure related to the health of the mitochondria because it represents the burn rate of your caloric needs.