how long can you survive on reserves and bread + h2o

This evening I began to feel really ill, my whole body started to tremble, no major convulsions to freak out over but enough to notice something was wrong. I remember being in the doctors surgery once as a child sitting on my mothers lap patiently waiting to see the G.P. I recall feeling the same warning signals. Shaking, blurred vision. dizziness and loss of balance. On that occasion I blacked out and fell to the floor straight out for the count. This time my legs started to buckle and I knew what was coming if I did not react fast. So I went to ground whilst I was still conscious and was thankful I had company just in case I did black-out. A similar thing happens if body sugar levels fall too much and I am guessing this was probably a mixture of the bread and water diet and a lack of sugar in my system. It seems that after 2 weeks the bodies reserves run low and so I guess this is the start of serious decline. Bread and water keeps you going for a few weeks but the body starts to suffer physically and mentally.