As a trail food there's also what our American cousins call GORP ( Good Old Raisins and Peanuts ) this is a bag of goodies to munch along the way as snacking ( or grazing as I prefere to call it ) keeps the tummy, body and brain fueled. Just make up some bags of peanuts (salted, honey or dry roasted) add some dried fruit (raisins, currents, dates, banana what ever you can get) but I like to spice things up with "treats" like M&M's, minstrals and the likes - chocolate in a hard case that wont melt. Munch on this and it keeps hunger down, keeps the body fueled with slow and quick release energy, and is pretty darn good.
Old staples like milled oats are great too as a) they expand in the stomach, b) good slow release energy, c) can be used at breakfast with milk powder for a cereal, d) added to soups and stews ( I always add some to mince at home to give flavour and bulk it out ), and you can make bannocks / oatcakes with a wee ticky water and some salt on hot rocks. Heck the Scottish army used to march on the stuff.
GB.