First why would Moshe need to be like the Malachai HaSharet, and second why does just purging himself of food and drink do so. Please point me towards sources for these questions rather then answering them directly. Thank you very much.
Benyamin Gilbert, Migdal Oz, Israel
Benyamin-
Try Ben Yehoyada (who argues with Rashi's interpretation here). You might want see Nitzotzei Or as well (who points out that this is the Rambam's source that one cannot live more than seven days without food).
If I may add my own sources, try Yoma 75b (where the Tana'im argue whether Man was "absorbed by the body leaving no waste" or "food of the angels"; both are true and complementary), and the many related sources that I cited in "Torah From the Internet" (Judaica Press, 1998), Parashas Mishpatim, as well as the Tanchuma cited there (Vayakhel part III) that says the Torah could only be given to "Ochlei ha'Man."
See also Shabbos 88b (the angels protest that the Torah ought to be given to angels and not Man), and Tosfos Kesuvos 104a DH Lo in the name of a Midrash (that Torah can only be absorbed by a person who has not allowed delicacies into his body).
In Chagigah 16a you will find a list of qualities that distinguish between Man and Angel. The list includes food-related processes and procreatory processes. Since Moshe already refrained from the latter, see Shabbos 88a, by removing the food from his body he no longer differed from the angels.
I hope that I have not been too lengthy, and that you find this answer helpful.
Be well,
Mordecai Kornfeld