The sense turns on the fact that dinner is a heavy meal, while supper is a light one. The precept was current in medieval Latin: post prandium stabis, post coenam ambulabis, after luncheon you will stand still, after supper you will walk about.
After dynner, talke a while, After supper, walke a mile.
[1582 G. Whetstone Heptameron of Civil Discourses E3]
That olde English saying: After dinner sit a whyle, and after supper walke a myle.
[1584 T. Cogan Haven of Health ccxi.]
‘The physiological reaction to a heavy indigestible meal‥ seems to be to sleep it off.’ What it all seems to boil down to is the old adage: After dinner rest a while, after supper walk a mile.
[1979 Daily Telegraph 24 Dec. 3]
Related to: health
Bibliography of major proverb collections and works cited from modern editions is available here.
