How Do You Define "Full"?
According to Wikipedia, hara hachi bu is a Confucian teaching that instructs people to eat until they are 80 percent full. Roughly, in English the Japanese phrase translates to, "Eat until you are eight parts (out of ten) full" or "belly 80 percent full." The practice is ingrained in Okinawan culture, a place where life expectancy is one of the longest on earth (over 25% of Okinawans live to be 100, and in good health). Of course their plant-rich diet, full of anti-oxidants plays a part as well, but the hara hachi bu practice alone could have immediate and lasting impact on the health of everyone, everywhere.
If only the typical American had such discipline in eating - myself included. If we just paused, took a breath and asked ourselves, "do I really need another bite," we'd likely find the answer is no.
We've all heard that it takes about 20 minutes for the stomach's stretch receptors to indicate satiety, so if you eat until you already feel full, you've likely overdone it. So stopping at 80% capacity is a really good strategy to avoid that uncomfortable feeling of being "overfed" and in the long-run, in controlling our weight.
If you grew up in a household where it was common to "eat until your plate is clean" this may seem like a big psychological adjustment, but there are solutions for that - use a smaller plate, or just put 75 - 80% of what you normally would eat on your plate. I'm not trying to oversimplify this. It will take re-training and about three weeks of eating this way to reset the stomach muscle memory.
Another way to think about it is to eat until we are no longer hungry, instead of until we are "full" - a practice I fully intend to practice.