Despite my Chasidic predilections, it always bother me when I see [healthy] people eating before davening. The gemara derives the prohibition from a PASSUK and some hold that it an actual di-oraisa. The Rambam and Shulchan Aruch forbid it etc. etc.
ואחד האוכל ואחד הנמנע מלאכול ובלבד שיכוון לבו לשמים!