From the Guidelines
A respiratory quotient of 1.2 indicates lipogenesis, as it suggests that the body is converting carbohydrates to fat, resulting in a higher production of carbon dioxide compared to oxygen consumption. This is based on the principle that the respiratory quotient (RQ) is the ratio of carbon dioxide produced to oxygen consumed during metabolism, and an RQ greater than 1.0 indicates that more carbon dioxide is being produced than oxygen is being consumed 1.
The possible answers can be evaluated as follows:
- (a) lipogenesis: This is the correct answer, as an RQ of 1.2 is indicative of carbohydrate conversion to fat, which generates additional carbon dioxide without consuming proportional amounts of oxygen.
- (b) ketogenesis: This is incorrect, as ketogenesis occurs during fat breakdown and would result in a lower RQ, not a higher one.
- (c) pure fat utilization: This is incorrect, as pure fat utilization would result in an RQ of approximately 0.7, not 1.2.
- (d) carbohydrates are the source of fuel: While carbohydrates are involved in the process, an RQ of 1.0 would indicate pure carbohydrate metabolism, not 1.2.
- (e) proteins are the source of fuel: This is incorrect, as protein metabolism would result in an RQ of approximately 0.8-0.9, not 1.2.
Key points to consider:
- The respiratory exchange ratio (RER) is equivalent to the RQ under steady-state conditions and can be used as a rough index of metabolic events 1.
- An RER greater than 1.0 can also be caused by CO2 derived from lactic acid or by hyperventilation, but in the context of a steady-state RQ of 1.2, lipogenesis is the most likely explanation 1.
From the Research
Respiratory Quotient Indications
- A respiratory quotient (RQ) of 1.2 indicates that the body is utilizing carbohydrates as the primary source of fuel 2.
- An RQ greater than 1.0 suggests net fat synthesis, which is often seen in patients receiving parenteral nutrition with glucose and amino acids 2.
- The RQ value can also be influenced by the type of fatty acids being oxidized, with different fatty acids yielding different RQ values 3.
- However, an RQ of 1.2 is more likely to indicate lipogenesis, which is the process of producing fat from non-fat sources such as carbohydrates 2.
Fuel Utilization
- Carbohydrates are the source of fuel when the RQ is close to 1.0, as they produce more carbon dioxide than fat or protein 4.
- Pure fat utilization is typically indicated by an RQ of around 0.7, although this value can vary depending on the type of fatty acids being oxidized 3.
- Proteins are not typically the primary source of fuel, as they have an RQ of around 0.8, which is lower than that of carbohydrates but higher than that of fat 4.
- Ketogenesis, which is the production of ketones from fat, is typically indicated by an RQ of around 0.7, although this value can vary depending on the individual and their metabolic state 4.
Conclusion Not Provided
As per the instructions, no conclusion will be provided. The information above is based on the available evidence and should be used to inform decisions.