What Causes Numbness In Legs?

my son is 15 all of a sudden he said his stomach hurts its been half a hour i ask him to lay on the floor i felt where his pain is its in the middle of stomach and goes up to middle of ribs he had dinner about 3 hours ago and he has use his bowels ...another thing he said his legs go numb when he is hungry as soon as he eat the numbness goes away