Greentext

A general rule of thumb is that you can go 3 days without water, 3 weeks without food and 3 minutes without oxygen.

You would not die of fasting for three days unless you're severely diabetic and had a hypoglycemic shock, as long as you hydrate properly.

If you were stuck in a desert though, sweating your ass off, and only had purified water (and in this hypothetical you're on a planet which has 80-hour days so there's no cool nights in between), you would probably die.

But of a lack of electrolytes, not hunger. Sodium is a critical electrolyte that, along with potassium and chloride, helps to deliver water to your body's cells.

So with a few of those single-use salt bags from McD you'd be fine.

I'm a supply-core NCO (in the reserve tho) and my job was literally keeping soldiers fighting fit. We went over a lot of things related to things like these.

Barring any severe medical conditions, people can fast 3 days with water.

But remembering electrolytes is important. During the summer, we'd add a spoon of salt to every 30l water jug, to prevent the troops from dehydrating. Still, despite that, going for a piss got aptly nicknamed "tossing syrup", as the piss had a consistency of maple syrup, more or less. (I lost 10kg in my first two weeks of basic training, which was in July. A hot July.)