someone's eyes are bigger than their stomach
US /ˈsʌm.wʌnz aɪz ɑːr ˈbɪɡ.ər ðæn ðer ˈstʌm.ək/
UK /ˈsʌm.wʌnz aɪz ɑːr ˈbɪɡ.ər ðæn ðer ˈstʌm.ək/

1.
目が胃袋より大きい, 食べきれないほど取る
to take more food than one can actually eat
:
•
He ordered three main courses, but his eyes were bigger than his stomach.
彼はメインコースを3つ注文したが、彼の目は胃袋より大きかった。
•
I think my eyes were bigger than my stomach when I filled my plate at the buffet.
ビュッフェで皿に盛り付けたとき、私の目は胃袋より大きかったと思う。