Naw, sleep isn't even necessary by rules. Only for casting.Regulate Temperature makes me think of meditating Buddhist monks... perhaps also one that will allow you to go without food or sleep for a little while longer? Wouldn't do so for drinking, though.
Food would make a sort of sense, but you can go so long without it not sure it'd be worth a feat.
Might also want to take a look at my Purge Stomach line of spells.And the Induce Vomiting one makes me think it'd go along well with my Tasted to some degree... I like it.
Found it before you even editted. HaEDIT: You have a leftover [/spoiler] tag at the end of your post, VT. Just sayin'.
Well, that'd be getting pretty powerful for a simple skill trick. Arctic animals with thick fur only get to Tier 2.I'd recommend simplifying Regulate Temperature to work with the temperature band and protection level system presented in the environmental books.