Question

Explain the response and the consequences of prolonged fasting on fuel metabolism by the liver.

Answer 1

As glucose is the primary source of energy for most of the body cells, complete absence of carbohydrate metabolism does not occur during fasting, But, the glucose available in the form of glycogen will be consumed, after that the liver initiates gluconeogenesis from non-carbohydrate sources such as proteins and fatty acids. The primary source of ATP generation in the liver during the fasting state is the fatty acid oxidation. During starvation, in response to the decreased glucose levels, body decreases the metabolic rate of the body. Actually, major part of the energy required during fasting is derived from fatty acid oxidation. Whereas some tissue such as brain cannot derive glucose by fatty acid oxidation, these tissues get some glucose through the gluconeogenesis at the expense of muscle protein.