Meaning
You can't function on an empty stomach — you have to eat first.
Example
Antes de começarmos a mudança, vamos almoçar: saco vazio não para em pé.
Before we start the move, let's have lunch — you can't work on an empty stomach.
Origin
A well-known Brazilian proverb (ditado popular). Its origin is not documented; the only explanation offered is the transparent image behind it — a cloth or leather sack stands upright only when it's full, so the sack stands for the body that needs food to keep going.
Sources: Ciência Hoje das Crianças, Poder360.
Practice idioms with the Idiom Trainer
Falando's Idiom Trainer teaches you to recognize idiom meanings and create sentences using them, so you can speak like a Brazilian.
More idioms
Água mole em pedra dura, tanto bate até que furaSteady, persistent effort eventually overcomes even the hardest obstacle.Filho de peixe, peixinho éChildren take after their parents — the apple doesn't fall far from the tree.De maneira nenhumaNo way; by no means; absolutely not. Used to emphatically deny or refuse something.dê seus pulosFigure it out yourself, manage on your ownser laranjaTo be a front man, to lend one's name for illegal or fraudulent activitiesse desenmerdarTo sort things out on one's own, to get oneself out of trouble (vulgar)dar broncaTo scold, to give someone a telling-offBora láInformal expression meaning "let's go!" or "come on, let's do it!"Chá de casa novaHousewarming party — a celebration to inaugurate a new home, where guests bring useful household gifts.Acertar na moscaTo guess correctly / To hit the nail on the head