The proverbial "Rule of 3" says you can live three weeks without food. Are there any documented cases of people actually living three weeks with no food in the wilderness and surviving?
For those who aren't familiar with the rule, it's that you can't live more than:
The rule of three may be a useful mnemonic to help prioritise or plan in a survival situation, but it is not necessarily going to be accurate. Survival without food is going to depend on many factors, for example, the nutritional state of the person at the start of their starvation and the amount of energy they expend during the starvation. These factors will shorten or extend the three week estimate.
One example of survival with negligible food intake longer than three weeks is the story of James Scott who survived 43 days lost in Nepal eating only some vegetation and a caterpillar. He documented the story in his book Lost in the Himalayas.
While not wilderness survival, according to this article from Scientific American, there are well documented studies reporting the survival of hunger strikers for up to 40 days.
On the three minutes without breathing rule, an extreme example that contradicts this is the static apnea (freediving breath holding) record of 11 minutes and 35 seconds.
I'd say none of those rules are "proven" - they're very, very rough estimates based on a very rough description of average. Some people will fall unconscious a lot sooner than 3 minutes with no air, some can last a lot longer.
In terms of food, David Blaine lasted 44 days suspended in a transparent box in London - there have been other reports of people lasting a lot longer, and some not lasting that amount of time at all. If you're fit and healthy with a fair bit of fat on you, your body will break it down and last a lot longer than someone who's (for instance) skinny and underweight. Likewise it depends what you do in those days - if you're hiking heavily without food, you won't last anywhere near as long as if you weren't going anywhere or using much energy.
There’s quite a lot of people interested in fasting for spiritual and health purposes. When fasting, these people don’t drink anything but water and don’t eat anything at all, their stomach simply pauses. And it’s not unusual to fast like this for several days or even weeks.
One of my friends tried a three-week fast and I happened to meet him just as he was ending. He was quite skinny, but appeared fully functional. Another friend of mine fastened for at least two weeks, I can’t remember the exact number. Both of them lead a normal life, the first one even kept running his usual kilometers and the second one kept working as a scientist.
I am not saying that you should try this or that it’s completely harmless. (Especially the return to normal food takes a long time and you must excercise a great care and discipline.) My point is that three weeks without food is nothing unheard of and you don’t have to be a walking corpse in the end.
I’m not sure if eating small amounts of food is better than eating nothing. During the first several days of fasting the body shifts to a different energy source, it could be that starting the stomach again would do more harm then good.
Anyway, if you happen to be without food for a week or so, there’s no need to panic. You’ll be uncomfortable, but you’ll be fine. You can even try fasting for several days to see how the body works in those conditions, but in that case please don’t trust a random stranger on the Internet and find somebody who knows what he’s doing :)
Real examples abound. The best one from a story perspective is Wallace's "Lure of the Labrador" An entertaining read for so many bad decisions. They were out 5 months, expected to live by hunting, and had only 2 months food with them. One died. The other two started out plump, and came back bone racks.
See also "Mutiny on the Bounty"
Neither of these stories is zero food and zero water. Both give insight as to what is doable.
