I wonder a bit on the "provide unlimited food and use that to determine what they should eat" - if applied to children we'd learn they should subsist entirely on a diet of candy and soda.
Briefly, Davis took a group of newly weaned infants in the 1930s and let them choose what and how much to eat from a set of 33 food items. The experiment was designed so that the caretakers would not influence the children's choices.
I don't think candy and soda were among the 33 items--I believe they were all reasonably nutritious foods but with very different mixes of nutrients. All the kids ended up choosing diets from among those items that fit well with their individual nutritional needs.
In other words, give people the illusion of choice, and they're more willing to accept your limitations. I don't see any evidence here that children (or anyone) have some kind of special insight into their own bodies' "nutritional needs" - to the extent such things are even individualized - but rather, that most people will eat a balanced diet when given the choice. E.g. none of the children became vitamin deficient because none of them chose to eat entirely one kind of food.
Which, to bring it back to this thread, I find it very unlikely that unlimited access is at all a universal good idea. Might have worked on 2 of our kids. Would fail dramatically on 1 of them, though.
Similarly, anyone that says that just give their pets unlimited access to food, is lucky to not have one that would just binge forever.
I didn't know until I had one that a lot of huskies will actually only eat when they're hungry.
It's usually nice, because I can just leave the food down and she'll eat when she wants. It's not so nice when I'm dog-sitting and she doesn't eat promptly, so the other dogs usually raid her bowl.
I wonder if bird parents feel guilty for digesting their chick’s supper.
Food has changed quite a bit in the last 90 years, especially the prevalence of processed foods and food designed to trigger various taste responses.
Forgot where it is, but I remember reading a study in which gradually-sweeter water was given to kids of different ages. A clear trend emerged: water became too sweet quicker for older kids. For infants, the water saturated before they stopped drinking.
In the case of animals, this would involve providing unlimited foods similar to what would be found in their natural environment.
If we gave kids their choice of naturally-occurring foods to eat, it probably wouldn’t be too terrible. My child was much more into things like broccoli and certain vegetables than I would have guessed.
Introduce processed foods and all bets are off, though.
In what sense is broccoli naturally occurring?
It's a heavily artificially selected vegetable not available outside very specific regions before the 20th century.
I'd assume that applies to the rest of the vegetables you've mentioned.