From the following foods, eat what you like, and eat as much (or as little) as you like:
- Eat meat, fish, animal fat
- Eat vegetables
- Eat fruits
- Eat real food, not industrial "Crap In A Box"
- Prefer traditional preparation methods (avoid novel industrial ones)
Try to avoid evolutionary novel foods like the following:
- Avoid seed oil ("vegetable oil")
- Avoid dairy and milk (especially pasteurized milk and dairy made from it)
- Avoid cereal grains, soy
Everything else? You need to find out yourself.
Is it some food your grand-grandmother would have had access to? Then it might be OK.
Can the food be produced only industrially? Oh, oh, better stay away from the stuff.
There is more, but for a start this should be enough.