First whole foods can include dehydrated vegetables and (cooked) beans which are easily available from outfits such as Harmony House (or others). Dehydrated foods are amazingly lightweight!
It’s not at all hard to make up meals consisting entirely of repackaged vegetable/bean combinations with added salt, spices etc. For example, Black bean chili with spinach for dinner. Also include peanut or almond butters, honey, some nuts, quinoa, rice or pasta, tortillas, crackers, hard cheeses etc
We ate this way on a 9 day backpacking trip with a scout troop; some of the boys were vegetarian and we didn’t want to have separate meals for them. We ate very well on that trip and no one went hungry or felt undernourished.
On the above outing we had three very young scouts (under 90 lbs each); they were each limited in how much weight they could carry (total pack weight around 20 lbs including food and water). So we were quite aware of the need to minimize pack weight for all as the rest of the group especially the adults had to carry most of the food and fuel. Since the group wanted to eat cooked meals for both breakfast and dinner, we packed a significant amount of white gas.
I have since eaten that way on all my backpacking trips. I buy the ingredients (dehydrated veggies and beans) from Harmony House and create my own meal packets (vacuum sealed for each dinner).
I’m not vegetarian I’ll also carry some jerky or meat bars or salami to supplement my lunches.
Breakfast is mostly some combination of nuts, seeds (hemp, flax etc), whey protein powder on some days and coffee/tea. Lunch is mostly nut butter, honey, tortilla wraps jerky or cheese and crackers. Rarely I’ll carry a Probar or a gel if I need some extra calories.
Dinner is a cooked meal – rehydrated veggie/bean mix with olive oil or ghee (clarified butter) for fat and quinoa or pasta. Sometimes some cheese. You could also add soy “chicken” and other faux meats – I don’t personally like it much.
On the same boy scout outing, I think for 10 people over 9 days eating this way our total food expense (not including fuel) was less than $300 – just over a $1 a meal per person (10 people x 9 days x 3 meals per day = 270 meals). We weren’t even focused on the food expense; we were all quite surprised how little we had spent on food after the fact.
We did get a 15% price break from Harmony House.
Before the trip a couple of the adults on the trip were concerned about not being adequately nourished and packed extra food for themselves (jerky, bars etc). They brought all the extra food back. This was a pretty strenuous trip through the rugged Yosemite back country around the Grand Canyon of the Tuolumne, Ten Lakes etc