Plate sizes have changed over the years. Have you ever been to a thrift store and seen the olde plate sizes? They are so much smaller. They were smaller people then too. Now we have the fashion of big plates and small servings with enough room for the raspberry coulis to create artistic drapery.
But we don't eat like that normally. We fill the edges of same said plate because as a rule, we don't like gaps or voids or space, it makes us nervous. And who is going to prepare raspberry coulis, to fill the gaps, when you're working 9-5?
It's a game to adjust portion size and not easy to do. I recommend using plates/bowls that have pictures on them so you can serve yourself to a petal or something. Or buy smaller crockery so there is the illusion of eating an entire bowl, for instance.
Best way to work around the limbic brain is to bamboozle it.
The best bamboozling this side of the Rio Grande is to also do breathwork, alternate nostril breathing to be exact, which calms the emotions responsible for over eating. And it works great because it's not direct focus on the subject.
These two together is a winner. Try it.