Help me with a little thought experiment. In this thought experiment we rank the importance of various things by how quickly we will die without them. Based on this we might make some interesting observations. Here is how I order things:
1-Air. Death in a few minutes without it.
2-Water. Typically a few days is the outside for overt dehydration. Increased exertion and temperature can cut this to a few hours.
3-Most would put food here, but I think that is misplaced. Even lean people have about a month’s worth of fat and protein on their bod’s. Want to kill someone in about a week-10 days? Keep them awake. In 3rd position, before food, I’d put sleep.
This is a pretty general list, someone like Greg Everett might structure it as such:
You get the idea…what’s going to kill you if you go too long without it.
Back to my first list, the lack of air thing is pretty obvious. Plastic bag over the head and you are done for. This is a severe , acute exposure that our systems have no ability to adapt to. What about chronic lower level hypoxia? We have slick mechanisms for reading CO2 and O2 levels in the blood and a lack of O2 saturation stimulates the upregulation of erythropoeitin (EPO). We make more red blood cells and, up to a point, we can adapt to hypoxic situations. Another interesting mechanism for adapting to an oxygen scarce environment is…anaerobic exercise. That is a whole other blog topic, but it really makes sense when you think about it. Want to work efficiently without oxygen? Train without it.
The next thing on the list was water. Severe water restriction can kill us but we do have mechanisms which allow us to adapt to lower water intakes. This can change our relative water needs dramatically by tweaking aldosterone and antidiuretic hormone (ADH).
Skipping down to food, we have quite a capacity to survive without food. If you have ever read Good Calories, Bad Calories, you are familiar with the adaptations inherent to starvation and how wickedly efficient our bodies can become when facing a starvation situation.
Now sleep. We see NO favorable adaption to sleep deprivation. Some people tolerate it better than others…interestingly, the folks who can “get by” on less sleep die younger…so there is no free lunch here. You do not build a callous, you do not up-regulate this or that enzyme system…you get fracking sick and have a boat load of problems. What I take from this is we are REALLY wired to get a restful nights sleep all the damn time. You can get by, but at very high cost.