The hidden health stat is supposed to represent immune system function, toxicity of diet, ability of the body to deal with hardships and so on.
It is the difference between eating salads from fresh vegetables, and eating deep fried lard, chasing it with coke and popping a multivitamin to meet the daily requirements.
The problem is, it is mostly random, barely affected by diet. A lucky meth addict can feasibly end up healthier than an unlucky health nut who somehow manages to find fresh fruit all year long.
A stack of apples a day won’t keep the doctor away, unless you’re really good at throwing them.
Related issue: https://github.com/CleverRaven/Cataclysm-DDA/issues/21155 - tl;dr the randomness is so strong that it looked like there is a bug that caused health from food to have an effect opposite to the intended one.
Trying to work around this requires gorging on the fruit past satiety, accelerated metabolism or some sort of bulimia.
To fix this, we’d need some sample diets and expected health ranges for them.
Simple ones would work best. For example, diet of potato chips and energy drinks (nothing else) resulting in health in range of [-20, -50] after 14 days, and diet of cranberries and mineral water giving range of [50, 100] after a month.
Alternatively, someone to crunch the math and provide a bunch of plots for how could it look.
Health is in range [-200, 200], but values below -150 and above 150 should probably be reserved to hardcore abuse (advanced alcoholism, faulty bionic) and strict health fanaticism respectively.