Even if you pack your diet with super foods like blueberries and broccoli, you could still be shortening your life if you’re not following the 80% rule. Why does this simple rule help you live longer?

Because it means eating only 80% of the food on your plate, which is one of nine healthy practices shared by people in longevity hot spots around the world. In fact, researchers found that in Okinawa, Japan (aka The Island of the Immortals), residents say “Hara Hachi Bu” before every meal. This phrase, which translates to “belly 80% full,” is their reminder to stop eating when their stomachs are 80% full.

We may not see an influx of 100-year-olds walking the earth, but the growing interest in leading a longer, happier life is a mature market trend we should all keep an eye on.

Next week, we’ll reveal what you should be eating.