I once got talking to a doctor on a train about health, nutrition and longevity and was fascinated to learn about something called 'Cone Theory.
' Apparently, at any given time, a person's physiology can be defined according to its current level of resource and the level to which the resource must drop for him or her to die.
As we age, the current resource level slowly drops and the death threshold slowly rises, creating a graph of two slowly converging lines.
When the lines join and you reach the tip of the cone, it's curtains.
Most people, he said, were not aware of the size of their gap at any given time.
Recently, after several years, I remembered the conversation and decided to look into Cone Theory for myself; but I was surprised to find that Google returned no hits for anything meaningful.
If such a theory officially exists, it's certainly not called 'Cone Theory'.
Maybe I just got the name wrong - or perhaps the man was not a doctor but a pathological liar.
We are unlikely to find out unless he happens to read this blog and is gripped with a desire to come clean.
Thinking about it now it just seems like another way of saying that when you get unhealthy you die and that susceptibility for an individual varies with time and also varies between individuals.
In other words, common sense.
Yet it got me thinking about something else that has bugged me for years - the fact that some people appear to have a totally different discomfort threshold from me.
Some years back my Dad had a friend he cycled with.
His friend showed up each Saturday without fail, despite having invariably drunk half a litre of whisky the night before - and the night before that.
In fact this guy was Jack Daniels' best customer.
Yet he was able to keep up with, and often out-perform my Dad, a pretty fit guy.
We were astounded by his ability to function happily in this way in spite of his drinking habits.
Similarly, I have friends who in years gone by were able to drink for most of the night, get perhaps 3 hours sleep, go to a football match and then continue to drink for the rest of the day, perhaps rolling into bed in the early hours of the following morning.
I'm pretty sure I could have done the same thing if you'd offered me enough money, but I would have hated it - my body would have been screaming at me in all kinds of ways, urging me to go home to bed.
My friends were offered no such incentive and they loved every minute.
I can think of a few reasons for this apparent disparity.
My friends may simply have been built of sturdier stuff.
There is a documentary that has aired on UK TV called 'Inside Britain's Fattest Man', about a guy called Barry Austin.
When the program was made, Barry had been eating and drinking to heroic excess for several years and achieved a weight of around 50 stone.
The narrator asserts (with no real evidence I should say) that Barry was able to do this and remain in apparent good health because he had incredibly well lubricated intestines and an uncommonly strong liver.
Needless to say, it was mentioned that even Barry's top drawer organs would begin to feel the strain if he continued with his lifestyle.
Clearly in Barry's case, one of the reasons he was not currently feeling the strain was that he had a better body.
On the other hand, it could equally be that my friends were no sturdier, but simply had a different attitude to discomfort.
As children they may have learned to associate the body's signals about wear and tear with opportunities for enjoyment.
The whole framework of their perception could have been skewed towards decreased sensitivity - or conversely mine towards increased sensitivity for some other reason.
Finally, I wonder whether as well as varying genetically in our robustness, we also vary in the strength of the signals our bodies send to our brains? Perhaps my friends were simply getting weaker signals from their bodies and therefore genuinely didn't feel as bad as me even though they were in the same shape.
A word you hear a lot in this context is 'constitution.
' I once heard Rod Stewart being interviewed about his partying experiences with Elton John.
On one occasion, says Rod, when Elton was at the peak of this cocaine use, they stayed up all night, drinking and doing, as Rod calls it 'How's your father'.
Abruptly, at 8am Elton stood up and announced they would go and watch Watford play football.
I can't find the interview on YouTube, but I recall the phrase "He's got an incredible constitution.
" The word 'constitution' seems to encapsulate the three explanations perfectly.
However, my experience is people tend to assume it's the first one that applies - in other words, they feel okay, therefore they are.
So in spite of the fact that I have apparently been hoodwinked by a pretend doctor with a pretend theory (I have been confidently telling people about Cone Theory for years) I find myself warming to its theme.
For me, the main takeaway is that no one can really be sure whether they are getting the full story from their brain.
Rather like the president or prime minister, they only have their advisors' word for how things are looking outside the office.
Do I have a congenitally weak body and will therefore hit the peak of my cone at the same time as my hard-drinking friends in spite of all those nights I went home? Or am I blessed with a set of uncommonly honest advisors, whose candour will ultimately add years to my life?