Glucose-Alanine Cycle | Cahill Cycle 

The Glucose-Alanine Cycle also known as the alanine cycle or Cahill cycle, is the series of reactions in which amino groups and carbons from muscle are transported to the liver. It is quite similar to the Cori cycle in the cycling of nutrients between skeletal muscle and the liver. When muscles degrade amino acids for energy needs, the resulting nitrogen is transaminated to pyruvate to form alanine. This is performed by the enzyme alanine transaminase, which converts L-glutamate and pyruvate into α-ketoglutarate and L-alanine. The resulting L-alanine is shuttled to the liver where the nitrogen enters the urea cycle and the pyruvate is used to make glucose.
This Process explains why BCAA is needed during fasting , why BCAA is used as a supplement in Body Building.
The BCAA provides Proteinogenic Amino Acids which are capable of building the proteins.BCAA in humans are luceine ,isoluecine and Valine.
It is an alternate source of energy during fasting but is less efficient than Cori Cycle.