Christians have the New Covenant. No diet therein.
Man does not live by bread alone, but by every word that proceeds from the mouth of Elohay!
IJeremiah 31:31 Behold, the days come, says YHWH, that I will make a new covenant with the house of Israel, and with the house of Judah: 31:33 But this shall be the covenant that I will make with the house of Israel; After those days, says YHWH, I will put my law in their inward parts, and write it in their hearts; and will be their Divine Author(ity), and they shall be my people. 31:34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know YHWH: for they shall all know me, from the least of them unto the greatest of them, says YHWH: for I will forgive their iniquity, and I will remember their sin no more.
Isaiah 59:21 As for me, this is my covenant with them, says YHWH; My spirit that is upon thee, and my words which I have put in thy mouth, shall not depart out of thy mouth, nor out of the mouth of thy seed, nor out of the mouth of thy seeds seed, says YHWH, from henceforth and for ever.
So technically we do have a diet i.e., every word that proceeds from the mouth of YHWH! And The Word which comes from heaven is the true bread that gives eternal life unto those who eat his flesh (=meat=truth), daily! We who believe no longer attempt to teach, but share with our neighbor, as bread is to be shared.
Now seeing how our bread is given daily, who knows what word/law YHWH will put in yourheart for you, he may prescribe something for you, which you did not expect, will you be able recognize that it is him speaking: Because we do not know what is on the menu for tomorow, it is presuptuous to say YHWH will not change my physical diet.