What had Esau been doing all day? As usual he had been occupied as “a cunning hunter, a man of the field” (verse 27).
What did he say to Jacob? Not, “I’m famished”, but “I’m exhausted: I’m at the point of death”.
Jacob gets criticised by some Bible scholars for exploiting the situation and demanding the birthright in exchange for the lentils, as well as for subsequently gaining the old father Isaac’s blessing which was meant for Esau (note the similar-sounding words, b’chorah – birthright – and b’rachah – blessing).
Esau surely also deserves a rebuke, not simply for being rough, uncultivated and irreligious, but for letting himself go all day without eating.
There is such a thing as over-eating: there is also such a thing as under-eating. The needs of the body ought not to be neglected, for religious as well as other reasons.
The body cannot function without food and drink, nor can one do mitzvot if the body is crying out for food (see Rambam’s introduction to his commentary on Mishnah Sanhedrin chapter 10).