It is funny that we think of ourselves as having a weight, when that must be one thing about us which varies all the time
I first really thought about this when a friend who was not exactly on a diet but was watching her weight & hoping to lose a little told us proudly that she had lost half a pound that week
How could she know? Since even a pint of pure water weighs a pound & a quarter (unless you are American), ones weight must easily vary by ±½lb during a day. Choose the right moment to weigh yourself & hey presto!
In fact it is not all that long ago that it was quite hard to weigh a human being. Quetelet spent quite a bit of his paper discussing his methodology & describing the equipment used. Babes in arms & grown ups were relatively easy, but toddlers & young children were a nightmare – they just could not be persuaded to stand still for long enough. The solution was to have them held in the arms of an adult (of known weight)
Even today there are unexpected ways we can be misled by (or fool ourselves with) our scales. The ordinary step-on kind at home will vary according to whether they are standing on a tiled bathroom floor or the bedroom carpet
And then we weigh more at the equator than we do at the North Pole (or is it the other way round?)
I have not been able to find anything which looks at, or plots, diurnal variation in a persons weight – well it’s not really a very interesting question I guess. Of more value is the study of time taken to digest & metabolise food, not how quickly we dissipate its mass
I did once see a paper about variation in height however. If I remember rightly we are taller when we get up in the morning (muscles all relaxed) than when we go to bed at night (tense & bowed down by the cares of the day). Not by enough to concern most of us, but if loss of height, or failure to grow, is of serious medical concern, enough to make it important to check progress by measuring the patient at the same time each day
For the rest of us, if we want to minimise our BMI the answer is to organise a weigh-in session at the North Pole (or the Equator) first thing in a morning
Cartoon by PJ Souter
