"Avoir les yeux plus gros que le ventre"

Analyses:

Avoir : To have
les yeux : eyes
plus gros que: it's a comparative. We said: plus + adjective + que (more + adjective + than) or moins + adjective + que (less + adjective + than).
gros : big
le ventre : the beli (stomach in this context)

Meaning

The translation will be something like "To have eyes bigger than the stomach"

Example

My child felt really hungry. He took 3 meals just for him. But he ate just 1.
Il a les yeux plus gros que le ventre !

And you, do you have sometimes "les yeux plus gros que le ventre" ?

:)