Ok, first up I believe that there are some rules about starvation somewhere in the 1st edition books, most likely in the Earthdawn Survival Guide along with the dehydration and other ailment rules. I'll have to get out the old hardcopy and check through, but I'm pretty sure that it indicated that you couldn't recover "hunger strain/damage" with a character's daily Recovery Tests until they had eaten. I believe its the same for dehydration strain/damage recovery. Try and get back to you on this, but it'll take me a week or so, OK
As for the minimum daily nutritional intake requirements of Namegivers, well in my campaign I've allocated rations and other provisions (IE: Hunting, Fishing & Foraging Test results) into Units. A Unit of food is approximate to one meal's worth (rabbit or other small game animal/fish, bowl of porridge and small loaf of bread, etc), whereas a Unit of water is about a pint (20fl oz). To remain healthy, in an average active lifestyle, Dwarfs, Elves, Humans, Orks & T'skrang require 2 Units each of food and water per day. Trolls require 4 Units each per day due to their greater mass. Obsidimen and Windlings, by contrast only require 1 Unit each per day. Windlings because of their small size and Obsidimen because of their very slow metabolism - seeing as they can effectively shut-down their systems and hibernate, food consumption isn't all that of a demanding problem for them. Note that these are the minimum requirements and eating and drinking more will be recommended, especially if there's a lot of active adventuring. Resonably safe to double usual daily Units without gaining weight in this case.
Hope it helps. As for the PCs in the cave, hope they have some survival skills for foraging underground. Hmmmm, worms and beetles and mosses and shoe leather. Tastes better than dwarf mine rations eh?
