Anybody for Dragon Chow?

[obloquy]

Balrogs were spirits of fire. The fire they produced is to be considered metaphysical and thus not a product of physical combustion.

[Selmo]

Didn't Bilbo observe a faint glow around the sleeping Smaug?

I think this gives us a clue about dragon energy sources. The glow was from burning hydrogen.
Dragon wings are too small to lift their great bulk. In order to fly, dragons must be lighter-than-air creatures. The gas that provided the flame in the early, non-flying dragons also provided the flight capabilities in the later, more evolved, Great Dragons. The slow combustion of hydrogen via a catalyst would also provide energy for metabolism.
The hydrogen is generated in one of the dragon's multiple stomachs by the action of gastric acids on certain minerals, so, apart from rare forays to obtain protiens and vitamins, dragons eat rocks.

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[Rimbaud]

But I'll post anyway. On the dietary habits of fictional creatures. :/

I had always thought of dragons as snake-like, having a very slow digestive process, that allowed them to last for a considerable period on one meal. Multiply this by the vast life-span of a dragon, and a hugely sedentary/hibernatory lifestyle, and it only requires one set of pillaging and festing every so often to be more than enough. Add to this the occasional unwise forays of treasure-seekers, and you had a fairly robust diet, for a slow-lived creature.

Balrogs, on the other hand, had to eat plenty, to support those huge, somewhat redundant, wings. The clue is given later in the book - shadows and dust. So think of a Balrog as like a modern Dyson, with a little more flame.

[Mithalwen]

Actually this relates to a question I have pondered from time to time, could you starve an elf to death (don't try this at home children)? I mean I know they can be slain (although it takes more to kill an elf than a man) and die of grief but surely at some point their bodies must give out? Or could Maedhros have stayed on that rock forever? I know Legolas received all the sustenance he needed from Lembas and was less affected by other physical hardships but is the hardiness of the elves relative or absolute?

[Gurthang]

First off, I never realized that Rocks had Hydrogen in them!

All that about dragons producing hydrogen is pretty good, but all guess-work. I doubt it was really that way with dragons halfway floating. It would explain the balrogs fire though.

As for Smaug's glow.... I really have no idea. If it was hydrogen, it would probably be described more as a flame than a glow.

The elves on the other hand, were immortal, so it would make sense that starving couldn't kill them. But they had physical bodies that needed sustainance. So basically, they would not die from starvation, but they would be trapped in a nearly lifeless body. I don't know that that made much sense, but... that's all I can think of now.

[obloquy]

Elves were not actually immortal.

[Lindolirian]

Originally Posted by obloquy

Elves were not actually immortal.

He's got a point Gurthang. Elves were susceptible to disease, mishap, or famine although they were much more resilient than men. For example Beleg was wounded in the ambush on Amon Rudh and his wounds would have killed a man, but as we all know, his healing skills and Elf resilience let him come out on top. If Elves could not die of starvation, what is their motivation to make a sustaining treat like lembas, or even why would they eat outside of pleasure?
As for Maedhros, I think perhaps he might have been kept (barely) alive by Morgoth just so that he could stay and endure the torture rather than escape via death. Fingon just rescued him too soon for us to find out.
And as for dragon diets, see Rimbaud. His is the most sensible explanation.