Your stomach is trying to adapt. You're going from your body thinking there is a famine to actually eating right. It won't be a fun process. Especially considering you're actually supposed to eat about 5 small meals a day, as opposed to 3 big ones. And you typically eat only one big one.
Way to fuck with your body.
FP
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Come away, O human child!
To the waters and the wild
With a faery, hand in hand,
For the world's more full of weeping than you can understand.