CAESAR: Let me have men about me that are fat;
Sleek-headed men and such as sleep o’ nights:
Yon Cassius has a lean and hungry look;
He thinks too much; such men are dangerous.

William Shakespeare (1564-1616) English dramatist and poet

Julius Caesar, Act 1, sc. 2, l. 202ff (1.2.202-205) (1599)
    (Source)

See Plutarch.