Well, your body was once an unfertilized egg, but that's before it was alive. It got alive when the sperm kicked in. So in that sense, your body was once all the food you ate, too.
Here's another angle: Is the body so important to keep alive at all costs that we can cannibalize other bodies to keep it going?
There are other things more important that clinging to the body when the whole thing is falling apart. I accept, believe and am 100% convinced (and I'll add, have also experienced) that the real self is the soul, or atma, which is separately existing from the body. The body is essentially a vehicle, which the soul is currently using. When the body is no longer viable - through accident, old age or disease, the soul goes somewhere else. Where it goes is a whole 'nother topic.
But it is commonly accepted by those who agree on the existence of the soul, that what we do in this life affects or determines where the soul goes after he leaves the body. So to cling on to the body as though nothing were more important than that often leads to wrong decisions, and misuse of the body's purpose.
> Well, your body was once an unfertilized egg, but that's before it was alive. It got alive when the sperm kicked in.
ERRRR. Wrong. Both the egg and the sperm are quite alive. If the egg is dead when the sperm shows up... nothing happens. Maybe you're born undead, fangs and all....
> Is the body so important to keep alive at all costs that we can cannibalize other bodies to keep it going?
Situationally dependant. Some 23 year old decent person who needs kidneys... why not? Some 85 year old scumbag who needs a new heart? Ummm...
> The body is essentially a vehicle, which the soul is currently using.
Ah. This is, essentially, the hear of the matter. At what point does the "soul" enter the person? If it is at conception... what does that imply for identical twins? Because they start as a single fertilized egg, which happily divides normally for a while, till something happens and the gamete splits. Does the soul split in two? Or does a second soul show up? And if that's the case, how about those cases where the two separate embryos merge back together? Does one soul go away? Do the two souls merge into one?
Now, if'n you're planning on legislation based on this... it's up to you to *prove* when the soul entered.