Thanks for the warm welcome, Gold Coaster! I think I've finally found my peeps! (teehee)
I've never noticed a problem with weight gain, although you guessed right they are very much free range. They go for long journeys through the forest all day. Though my personal philosophy is that eating fat does not cause weight gain, instead the culprit is usually too much carbohydrate--breads and sweets and such. For chickens as for dogs and people too. But that is another conversation altogether!
I did forget to include the dislikes. They are more difficult to catalog, because how does one separate the degrees of dislike beyond the point where they simply don't eat it? Anyway, here goes.
Potato peels. I know, they are supposed to be bad because of solanine, which is probably why they don't eat them. I just throw all food waste out in the compost heap and they go through and take what they want. Which is almost everything.
Onion skins. Again, something I don't actually feed to them, but something I've noticed they ignore, and no surprise there.
Dryopteris ferns. They pick at most other ferns they find in the forest, but they leave the Dryopteris (wood fern). They seem to have good enough instincts about what to eat and what not to.