The energy you burn up from that exploratory mining can be made up with a few hours questing. The number of double digit hunger reductions I get isn't even funny. I'll note I get a lot of 1-5%, too... Looks to be relative to how much the hunger bar is filled, I think, and bit of dedication to doing quests.
Exploratory mining is good advice. you're not nerfing your character any in the long term, but you are trading off some. With the early metal, you can get a pickaxe, meat grinder for sausages, plus more, and be a bigger contribution to your group (or yourself) than by waiting days more to push enough exploration for rustroot, and then there's no guarantee that you can reasonably get to the metal you found without cave ins or needing a significant increase in strength.