The value for R changes under different metabolic conditions. When a person is using exclusively carbohydrates for body metabolism, R rises to 1.00. Conversely, when a person is using exclusively fats for metabolic energy, the R level falls to as low as 0.7. The reason for this difference is that when oxygen is metabolized with carbohydrates, one molecule of carbon dioxide is formed for each molecule of oxygen consumed; when oxygen reacts with fats, a large share of the oxygen combines with hydrogen atoms from the fats to form water instead of carbon dioxide. In other words, when fats are metabolized, the respiratory quotient of the chemical reactions in the tissues is about 0.70 instead of 1.00. For a person on a normal diet consuming average amounts of carbohydrates, fats, and proteins, the average value for R is considered to be 0.825 ( Hall & Guyton, 2011, p. 504). Calculated based on the formula, there is about a total of 3000 ml of O2 entering into the body every minute, and a total of 3000 ml of CO2 expelled from the body every minute.