How much food one needs while walking varies greatly between people, and with the weather and the level of exertion. And how much weight matters depends on how long the walk is.
The following are my current choices of food for a weekend trip.
For breakfast I carry muesli, with either powdered milk or the small 125ml UHT containers (one serves two people). This is flexible, since I can eat just as much muesli as I feel like.
lunch & snacks
For lunch I take cracked pepper vita weats, with salami. The vita weats are easy to eat, don't break/crumble too easily, and I can eat as many as I feel like — six or seven usually does me.
I'll usually take about 200gm/day of chocolate coated peanuts and/or chocolate coated licorice. I add an extra 150gm or so of chocolate for emergencies. I take 150gm/day of dried fruit — dried pears are probably my favourite. And I throw in 3 muesli bars per day.
My current favourite meal base is couscous. This is faster to cook than rice or pasta, can be left in cold water and then eaten in an emergency, and doesn't stick to the billy. To supplement that I add dried peas, dried mushrooms, onion flakes, and suchlike, and then throw in a can of tuna or something similar.
I also carry two or three soup packets per day, having soup before dinner and maybe at breakfast and/or lunch.