Wiktionary
on a full stomach
adv. (context idiomatic English) Directly after eating, after a meal.
Usage examples of "on a full stomach".
I elected for an early dinner, for I did not expect to have much opportunity to eat later that night and I had the suspicion that whatever the fates had in store for me that night had better not be encountered on a full stomach.
Maia Favonia, your mother brought you up to know that bathing on a full stomach can give you a seizure.