How does caffeine tolerance develop?
Caffeine has a similar chemical structure to adenosine – a substance that causes you to feel tired. When you drink caffeine, the molecules bind to the receptors in the brain that are usually “reserved” for adenosine. Essentially, what this does is “trick” your brain into thinking that you’re not tired (because of the apparent lack of adenosines). This, unfortunately, doesn’t last.
According to research, the regular consumption of caffeine increases your body’s production of adenosine receptors, which increases the likelihood of adenosine going where it’s supposed to. In turn, explaining why you’d need a higher dose of caffeine to beat the fatigue over time.