Its quite common with prisoners on hunger strikes. Apparently the feeling of hunger stops after a few days. Have to mention that you should be rather careful with that, the long hunger strikes where people died after month were with a forced feeding tube. With 20 days of total starvation you are already up there.
A holocaust survivor once told me her mother died after liberation of the camp by English troops, because they started eating the ample supplies that the guards had kept for themselves. Truly tragic.
