You are taller before breakfast
Most adults lose about a centimetre of height between morning and night, as the spinal discs compress, and regain it lying down.
Established2 min read
Intervertebral discs are gel under pressure. Upright, they lose fluid and thin. A night horizontal lets the fluid back in. Studies of the daily curve find a loss on the order of a centimetre, sometimes more in the young and less in older backs.
Astronauts meet the extreme case: without the daily load, the spine lengthens by a few centimetres, and back pain in orbit is common. They return to their old height after landing. The discs, not the bones, did the changing.
Caveats
- The amount depends on age, load, and the state of the discs. A centimetre is typical, not a rule for every back.
- It is not growth. Bone length is the same at dinner as at dawn.
Sources
- 1Reilly T., Tyrrell A., Troup J. D. G.. Circadian variation in human stature. Chronobiology International 1, 1984.