Board Thread:Shingeki no Kyojin Manga/@comment-24930713-20150609084033/@comment-5774380-20150616231228

No, it's impossible. It's a matter of mass. Cellular generation (including the disease that you mention) is made by metabolizing food into cells, but a human body doesn't have enough mass to generate 15 meters of cells, and I don't see shifters eating 2 tons of food before transforming.

This is even more noticieable in the cases of Bertolt and Rod. It would be impossible for them to generate bodies of 60 and 120 meters respectively with the mass found in their bodies, because the resulting Titan would have so low density that it would not even remain solid, it would become gas.

The transformation into Titan involves an increase in the mass, this is confirmed from the fact that the Titan becomes heavy enough to crush people, horses and buildings. But since the Titan body evaporates without a trace after it dies, this indicates that it's not made of regular cells; hence my theory that I posted in that link about it being made of compressed air or water vapor.