How does glucagon primarily affect the body?

Glucagon primarily affects the body by raising blood sugar levels. It is a hormone produced by the alpha cells of the pancreas and plays a crucial role in glucose metabolism. When blood sugar levels drop, glucagon is released into the bloodstream and stimulates the liver to convert stored glycogen into glucose through a process known as glycogenolysis. Additionally, glucagon promotes gluconeogenesis, which is the production of glucose from non-carbohydrate sources such as amino acids. This increase in glucose availability is essential for maintaining energy levels, particularly during fasting or intense physical activity, thus ensuring that vital organs, especially the brain, receive adequate glucose to function properly.

Other options relate to different physiological processes: lowering blood sugar levels is the role of insulin, while digestion regulation is more associated with hormones like gastrin and secretin. Promoting fat storage is influenced by insulin and other hormones, not glucagon, which primarily has a catabolic effect on glycogen and glucose. Understanding glucagon's role is crucial for comprehending the body's energy balance and hormonal regulation mechanisms.