Originally Posted by Ramon
I agree that caffeine has no metabolic value as a fuel for energy, but as a stimulant that helps you stay mentally alert, it's quite effective. Personally, I don't notice a diuretic response from it .
I only notice diuresis if I consume a lot of it within a short period of time, say 2 cups of strong coffee and some coke close together.
As far as stimulant part is concerned, it is tricky and highly variable. There is a lot of voodoo here even in hard science as "alertness" is hard to measure objectively. Some of the stuff from scientific standpoint doesn't make sense - it takes up to 45-60 min for it to get fully ingested, yet people report increased alertness within 10 min suggesting placebo effect, while others report decline in alertness 45-60 min after when it should be just at its early peak. Then there is a known tolerance development. What's very hard to measure is how long the effect would last.
The better studies, although not without flaws, that I've seen were done by the US military and NSW in particular, with a pretty good reasoning to use delivery forms other than ingestion.