Plasma insulin levels fall, leading to net catabolism of energy stores, while increased glucagon levels stimulate hepatic glycogenolysis and gluconeogenesis.

Plasma insulin levels rise to promote the breakdown of triglycerides, while glucagon levels fall to inhibit hepatic glucose uptake. 

Both insulin and glucagon levels rise simultaneously to ensure that most body cells continue using glucose as their primary fuel source. 

Glucagon levels fall to trigger the synthesis of ketones, while insulin levels rise to stimulate the "glucose sparing" effect for the brain.