10 January 2011

How my weight fluctuates during a day

About a month ago we bought a digital bathroom scale and retired the mechanical one after 22 years of faithful service. Ever since then the new scale has provided us with numerous occasions of weighty fun.

One project I did was the monitoring of the variations of my weight during 3 days. I am presenting the results as a graph with all weights expressed as percentages of each day's highest weight.


A person's body weight almost continuously changes: every inhalation increases the body weight, while every exhalation lowers it. Of course, such minuscule weight changes would be almost impossible to monitor against the much larger total body weight. But more significant changes in weight result from the meals and liquids consumed, profuse sweating and, of course, urination and bowel movements.

The true body weight of a person would have to be measured with no clothing and no food or waste in the stomach and the intestines and no urine in the bladder. At the same time, the person would have to be properly hydrated. This is much easier said than done.

The closest weight to the true weight can probably be obtained by monitoring the change of the body weight during a day.

The conclusion I reach from the graph above is that my body weight is at its lowest in the mornings and at its maximum at night right before I go to bed.

But what causes the body weight to decrease during the night? Some nights I get up to pee, but that can't be the sole cause of the weight loss during the night. One of my morning measurements were taken before breakfast and even before I sat on the toilet, but it was still 0.5 kg less than the previous night's maximum—too much to have resulted from one night time trip to the bathroom. That leaves us with the weight lost via breathing. I will try to tackle that in some other post.

So which of these weights come closest to my the true weight? Perhaps the weight given by the first reading of a given day.

1 comment:

Gav said...

An old WW2 airman I knew once remarked that you were heavier after a, er, bowel movement. Nobody disagreed. Just one of those things, I suppose. Never thought to test it.