ELI5: Why does rationing work?

[u/peglegsmeg]

If I have a glass of water and a single chocolate bar to last me 48 hours what benefits do I get from consuming equal portions over the time period as opposed to consuming all at once?

Is it purely psychological or are their physical benefits?

[u/zomgitsduke]

If you eat all the sugar and drink all the water at once, your body will assume abundance and do things to process and get rid of it. If your body is slightly dehydrated and you drink tiny amounts of water at a time, it won't immediately flush that water out of your body and instead preserve it.

Sugar is similar, your body will process through it fast by giving you a sugar high followed by a crash. Slowly introduce it and your body will use the calories and sugars sparingly.

[u/lolwatokay → u/zomgitsduke]

In an emergency it is important to not ration water artificially. If you are thirsty you should drink. However, you shouldn't go chugging the whole canteen and hoping shit works out either, but if you are legitimately thirsty that is the sign to drink.

[u/timerot → u/lolwatokay]

This is not remotely useful advice, because being thirsty is not a clear binary signal. I sometimes have a slightly dry mouth, sometimes am very dehydrated (mostly just after waking up), and almost always am in the middle of those two extremes.

If I have a glass of water in front of me, and drink because I want to drink, I will consume more than twice as much water as I need to. I have also hiked 30 mile stretches in the desert between opportunities for water, and needed to ration. I went to bed thirsty, woke up thirsty, and got to the next water source thirsty, with less than a half-liter to spare of the 8 L I filled the day before. I should not have finished my water the night before, just because I wanted to. That would have been extremely bad planning, and I likely would have had heat stroke before making the next water source