They have not been eating nourishing food.

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