I know on Yom Kippur, if someone is medically required to eat, s/he should do so with only a bit of food every few minutes, to avoid the full severity of eating "a full serving in one sitting."
On Tisha B'Av, does the same apply? Or is it simply "if someone has to eat they have to eat, but it's a sad day, so don't gorge yourself on delicacies."
I think I've heard both opinions, can anyone confirm this, or identify who holds what?