Leader Eating on Tisha B'Av

Question: Can one who is not fasting on Tisha B'Av lead davenning?

Answer: Abudraham quotes an opinion of R. Amram Gaon (Tur cites it in the name of R. Natan) that one who is not fasting shoudl not be the shatz on a Ta'anit Tzibbur.  Tur disagrees with this ruling and says that there is no reason that a person cannot say "b'yom hata'anit hazeh"--slightly different text than what we have, where it reads ta'aniteinu--even if not fasting, given that these are fixed fasts on the Jewish calendar.  This would distinguish this case from the general Geonic ruling that one does not say aneinu until minhah for fear that one will be overcome with hunger and need to eat later in the day, thus retroactively rendering the aneinu one said at arvit or shaharit to be a lie.  The obvious implication is that one is not fasting does not say aneinu. But Tur--actually based on Kol Bo on that other case--clearly holds that that consideration only applies to a case where an individual takes on his own fast day without any communal context.  Tur ends up concluding that it is preferable to have someone who is fasting as shatz, but clearly allows being lenient, such as if there is no one else prepared to do it.  We might add that one could also be lenient if feelings would be severely hurt.

In any event, Beit Yosef backs away from this and returns to the ruling of the Geonim and Abudraham and a number of others that one who eats is disbarred from leading on a fast day, and so he rules in the Shulhan Arukh in OH 566:5.
 
MA merely notes that if the non-faster already began leading, we can take a compromise position between Tur and SA: have the leader say aneinu b'yom tzom hata'anit hazeh in shomeia tefillah. That way, they don't add an entirely new berakhah, in case SA really takes a hard line on this issue, but we can rely on the Tur's logic not to consider such a statement to be a lie.  It does seem, however that MA woudl not want you to say ta'aniteinu, feeling that to be dishonest.  My own feeling is that that would not be such a big deal, given that the plural clearly refers to the nation's observance of the fast as a whole.  Note also that Hayyei Adam actually thinks that MA meant to say to add aneinu as its own berakhah and thus is essentially relying on the Tur if the person already started leading.
 
In any event, the bottom line: Never plan it this way, vastly preferable even if an error was made to replace the person, if tremendous pain or alienation would result as a result of replacing this person, then one could rely on the Tur's view--in my view even with the text we normally use, and even in the format where a new berakhah is added.  But the last option should only be used besheat hadehak.