Question

Define RQ. What is the RQ value for fats?

Answer 1

The respiratory quotient (or RQ or respiratory coefficient) is a dimensionless number used in basal metabolic rate (BMR) calculations measured using a respirometer.

Complete answer:
The Respiratory Quotient value shows which macronutrients are metabolised as different energy pathways are used for fats , carbohydrates and proteins. If metabolism consists exclusively of lipids, the Respiratory Quotient is 0.7, 0.8 for proteins and 1.0 for carbohydrates. However, much of the time , energy intake is made up of fats and carbohydrates. The estimated respiratory rate of the mixed diet is 0.8.
Respiratory quotient (RQ) or respiratory ratio can be described as the ratio of the volume of carbon dioxide to the volume of oxygen consumed during respiration. The value of the respiratory quotient is dependent on the form of respiratory substrate. It has a benefit for carbohydrates. However, it is often less than one fat because fats use more oxygen for respiration than carbohydrates.
This can be shown by the example of tripalmitin fatty acid, which absorbs 145 molecules of $O_2$ for respiration, while 102 molecules of $CO_2$ grow. The value of the RQ for tripalmitin is 0.7.
Practical applications of the respiratory quotient can be seen in extreme cases of chronic obstructive pulmonary disease, in which patients expend a substantial amount of energy on respiratory exercise. By the proportion of fats in the diet, the respiratory quotient is decreased, leading to a relative reduction in the amount of $CO_2$ emitted. This decreases the respiratory pressure of removing $CO_2$, thereby reducing the amount of energy expended on respiration.

Note: The Respiratory Quotient may be used as a measure of over-or under-feeding. Under-feeding, which allows the body to use fat reserves, decreases the respiratory quotient while over-feeding, which induces lipogenesis, raises it. Under-feeding is shown to have a respiratory quotient below 0.85, while a respiratory quotient greater than 1.0 suggests over-feeding.