When I was 29 I started a water only fast. I was doing it at home alone
with Dr Shelton (of Natural Hygiene) books as my  only advisor. I had been
eating a Standard American Diet most of my life. The fast lasted 48 days.
My weight went from 142 pounds down to 98 pounds. After the first day or so
I had no bowel activity for the next 35 days. On that day I suddenly had an
insistent urge. What came out was hard dark curved pieces and a white
frothy substance (mucus? possibly).  I would interpret those curved pieces
as old fecal matter that my body expelled on the fast. This makes me
question the idea that it never occurs. When I did a 41 day water fast a
year later, this did not occur. I had been on a Natural Hygiene diet during
the previous year. I also did not lose as much weight this time - only
about 25 pounds.