I used to follow FODMAP eating. Now pretty much have to eat onions as they are pretty much the basis of every soup I make.
It did help me a lot and I know of two others that never eat onion or garlic which are the most significant items to cut out.
It depends upon why you are following as to how much it will help and also how you can adapt..
To me it was eliminating everything and gradually reintroducing some foods in minimal portion and seeing if I could eat them.