Here in the UK the mainstream current healthy diet advice is to avoid processed foods, all soft drinks including "health" drinks. Eat five portions of fruit/veg a day, don't eat takeaways, don't eat sweets, avoid pastries.
There are lots of fringe diets, almost endless it seems, some of which are designed to combat particular health problems and some that are just downright dangerous.
Fussy about food is in part the consequence of affluence. Most of the world eats what they can get/afford.
Collecting what I consider possibly effective from the various diet advice I've read, I avoid seed oils, eat more beans, use more spices and herbs, keep the saturated fats to a minimum especially if one eats red meat. Drink water like it's going out of stock.
Eat more salads with as large a variety of leaves one can and make dressings with herbs and spices.
Sounds much like free range chicken feeding to me, apart from I've never seen a chicken knocking back a tin of Red Bull.
I'm on rustic Italian cooking currently for dinners. I've made a deal with my eldest for her and her husband to come around for dinner once a week and I'll try not to poison them. I'm hoping this will help sustain my wavering new found interest in cooking.
Definitely avoid seed oils. Olive and avocado are what we mostly use. Sometimes coconut.