Is cannibalism unhealthy/unviable?
All I have been able to find are some studies on the diseases you could potentially get from eating the brains of other humans but it seems like an easy problem to circumvent.
Of course, the seemingly deep psychological aversion to human dead bodies might have a good and equally deep biological reason but I have found very little evidence of that being true. Many humans handle dead humans every day and some people eat the dead as well.

TL;DR: Why not eat the dead?