Yom Kippur & other fasts/small quantities

[meha...@aol.com]

I promised before Yom Kippur to address the question of whether someone
who eats "pachus mik'shiur" less than the prohibited quantity of food
or drinks less than the prohibited quantity of fluids, for medical
reasons, is considered to have fasted or not. This interesting question
was raised by a respondent to this list.
Rav Shlomo Zalman Auerbach zatzal is quoted in the footnotes and
endnotes of Shmiras Shabbos Kehilchoso as being in doubt about this
point, but tending to say that he is still considered to be fasting.
Meromei Sadeh (Netziv, Yoma 73) is of the opinion that since we
consider a partial shiur to be a Torah prohibition and not just a
rabbinical prohibition, therefore the person who eats a smaller
quantity is still not considered to be fasting, and should not be
called to the Torah for reading caused by the fast.
Marcheshes says that such a person is still considered to be fasting,
since he is still feeling the innui (deprivation) by eating such a
minimal quantity. Marcheshes cites a Teshuvos Rivash and a Magen
Avrohom in support of his view, and adds that when he was unwell on a
Tisha b'Av he ate small qunatities and was still called to the Torah at
mincha. (It would seem to me there might be a difference between Yom
Kippur and Tisha b'Av, but the author of Marcheshes does not make such
a distinction)