I found some threads on steam, that concerned all random factors of the game but I did not find an answer to my question above.

It appeared strange to me that I can do a short-lengthed dungeon without a forced lunch-break but today, when I played a middle-lengthed dungeon, the game forced me to rest with my party a whole of 3 times, while I did not travel further than 5 or 6 rooms (I had to pass already cleared rooms, where the torch burns down more slowly).

PS: I would appreciate it, if the nowadays often seen superior sarcasm of very smart and skilled gamers would be kept to a minimum and instead I would just get an honest helpful answer. Thanks for your understanding ;)

I believe hunger was explained in the game's steam forum as an event much like the trap event and not as a diminishing stat that needs to be refilled. When you step on a certain tile in the hallway the hunger event triggers.

During a small dungeon run my party got hurt so I healed some of them with provisions, walked a few steps and got hit with the hunger pop up with no food left. Got some more damage. Thank you game :)

I haven't seen so very frequent stops for a picnic but I als also did notice that it happens far more frequently in explored corridors than in the virgin ones. I fits well to one of the early rules of this game where you were punished for avoiding taking risks. Here you can drop going backwards, prolonged fights (above 6 round) and traveling along explored corridors. Knowing how sadistic and deviant devs seems to be I avoid doing these wherever I can (except prolonged fights that you can turn off). You never know how the map will look like so just take more food than you need. It is cheaper than any anti stress therapy. For small maps take 8-12, medium 20-24 and long 30-34. The medium and long assume that for every rest you use 8 food to reduce stress and heal up. The rest you can use for healing or picnics or just dump close to the end and take some gems or gold.

Not sure on specifics but these two quirks have very noticable effects:
Sitiomania - Obsessed with food
Stress Eater - more stress more food consumed

I recall having seen an effect of the mandatory hunger break changing from 6 units to 8 units of food during the same crawl with just one character suffering one of the above. Wasn't particularly paying attention though.

@kosior: thanks for the enlightenment. I was wondering why in one situation they needed 8 instead of 6 for a rest, but I remember that one of my characters was suffering of sitomania.

@andre_geo: Concerning "punishment for taking no risk": I took a lot of risks talking "Curios" at the beginning, I didn't know, how they worked, so I ended up with my first characters all having ridiculously many negative quirks. Since I know, I can change the outcome of the interaction with curios by using bandages, healing potions, shovels, skeleton keys, etc. I only get neg quirks at the completing a dungeon or in the brothel ;)
The game makes much more fun, when you get a little understanding for the mechanics :D xD

Something off-topic: Can anyone tell me, what decides turning a negative quirk into a severly negative quirk (red skull and extremely high curing costs)

I agree, I feel it's far more frequent that the party needs to eat when walking in explored corridors.

Yeah Stress Faster is actually somewhat beneficial though highly situational as everything in DD.
Another interesting thought would be getting 4 x Bloodthirsty Rings to get complete immunity from the mandatory food breaks at the cost of some dodge iirc, I'm guessing one would still need to actually spend food on a campfire for the appropriate benefits.

I think that how much food you need while camping is also affected by the quirks/talismans (at least I remember needing 1 more when I had one stress eater with 50+stress).

As for the need to eat due to hunger - that just seems random. Had a run where in 5 corridors I had hunger 3 times, then could go another 5 ones without any hunger.

Okay :D ... so I guess it's almost impossible to get your characters out of negative quirks... Just gotta stick with the ones who I can live with. Okay, I mean I don't aim for getting rid of all neg quirks, I think that is part of the characters as well as the positive quirks?! I already fired some of my earliest characters, because they had 5 red skull negative quirks wiht very unsuitable habbits :D

These are actually the quirks I do get rid off :) ... I read the Curio Wiki entry and since I know how to use curios safely, I get much less negative quirks, but I still got some early characters, that are a really mess concerning their negative quirks.
I am a bit of a slow player, even after 20 Hours of gaming, I am in week 54 and mostly do apprentice dungeons. Now I got quite some level 3 characters, but I only did one veteran dungeon and my party got kicked ass very badly.
Long story short: I think, I earn not enough money with these "green" dungeons for curing all the negative quirks. But it's not like it bothers me :) the game taught me, that it's okay to play with flawed characters and it turned out, I like it :)

I've spent double the time and it's week 51 :) ! I very carefully prepare and overthink every move so that's why! I had to retreat on my first Veteran mission too. I realised that I actually had to upgrade equipment at the Blacksmith :D! My next run went flawlessly and semi-dark with a fully upgraded team. What will help you the most is a boosted healer.

It's fine doing mostly Apprentice mission. I think it's actually more profitable since the rewards seem to be the same (except for gold and trinkets) but the risk and the required investment much lower. I look for Long or Medium missions to increase loot per week.

Edit: make that triple in fact (60h) :P! I alt+tab a lot though.