Caffeine's antagonism of adenosine leads to wakefulness and consequently a higher metabolic rate compared to being asleep.

“And fourth, caffeine acts as an antagonist to adenosine, which offsets the sleepiness that we would otherwise feel from the accumulation of adenosine that occurs as we are awake for more and more hours throughout the day.”

“the main one we think about as an adenosine receptor antagonist so when we're thinking about what makes us sleepy or wakeful during the day particularly there's a buildup of adenosine and that what that's what partly or largely creates a drive to sleep in the evening and caffeine is an antagonist for adenosine and that's that's part of the reason why why it helps wake you up”

“even though you can't measure it you can actually manipulate it with something called caffeine and that can demonstrate to you how by the way we're up we're in America here I think there's a human that doesn't know what caffeine is you're get everybody's ears perked up like you're gonna mention like some new compound you just discovered in the lab yesterday it's some nice squirt no no”

“and in fact that's actually how caffeine works caffeine keeps you awake by lowering adenosine levels”