From what I understand (I'm not a scientist), caffeine doesn't "give" you energy, but rather makes your body ignore the tiredness, by turning off some of the machinery that would make you feel tired.
By having coffee in the morning and then in the afternoon, you build a "high" of caffeine that forces most of your "alert systems" to shut down. Once the peak wears off though, your body starts remembering to alert you to tiredness, which by then is often multiplied by the fact that by ignoring tiredness you've pushed your system hard when it was already tired. Hence you might feel like crashing.
On top of that, caffeine de-hydrates, so if you've not had enough water, your body will start to crawl.
On top of that, a lot (most?) people will have sugar with their coffee, and often quite a lot of it. Sugar can cause similar "crashes", particularly in the obese (like me), and obviously this combines with the abovementioned items.
> From what I understand (I'm not a scientist), caffeine doesn't "give" you energy, but rather makes your body ignore the tiredness, by turning off some of the machinery that would make you feel tired.
I have heard this too, but it doesn't feel like this to me, it feels like a stimulant getting me to a state above and beyond the one I would be in without the caffeine. There are also a lot of references to caffeine as a stimulant. So what is really going on?
By having coffee in the morning and then in the afternoon, you build a "high" of caffeine that forces most of your "alert systems" to shut down. Once the peak wears off though, your body starts remembering to alert you to tiredness, which by then is often multiplied by the fact that by ignoring tiredness you've pushed your system hard when it was already tired. Hence you might feel like crashing.
On top of that, caffeine de-hydrates, so if you've not had enough water, your body will start to crawl.
On top of that, a lot (most?) people will have sugar with their coffee, and often quite a lot of it. Sugar can cause similar "crashes", particularly in the obese (like me), and obviously this combines with the abovementioned items.