As soon as soda's swallowed, the pancreas is notified and rapidly begins to create insulin in response to the sugar. Insulin is a hormone the body uses to move sugar from food or drink into the bloodstream, where cells are then able to use sugar for energy. Within just 20 minutes, blood sugar levels spike and the liver responds to the insulin by turning sugar into fat for storage.
Within 45 minutes of gulping down a single 20-ounce glass of soda, caffeine from the drink is fully absorbed, and as a result your pupils dilate and blood pressure rises. The body produces more dopamine, which stimulates the pleasure centers of the brain — just like a low-grade line of cocaine.