They have not been eating nourishing food.

Answer: Option C

Nourishing : (of food) containing substances necessary for growth, health, and good condition.
Heavy : of great weight; difficult to lift or move.
Undercooked : cook (something) insufficiently.
Unhygienic : not clean or sanitary.
Poor : lacking sufficient money to live at a standard considered comfortable or normal in a society.

Antonym of Nourishing is Unhygienic