To really practice hara hachi bu, we need to tune in to our bodies, and our bodies' signals of hunger and satiety, or fullness. These are things which many of us have completely lost touch with.
We are surrounded by abundant food choices; we rarely experience a feeling of hunger. When we eat, we're often guided more by the time of day or the servings of food in front of us than we are by how full we're feeling.
Famous experiments by behavioural researchers have found we will unconsciously eat more when we're served larger portions; it's very easy for our brains to override our bodies' natural signals.
So to eat until we're 80 per cent full, we need to understand what that really feels like.
That means eating, to use a well-worn term, mindfully. To eat mindfully, we need to give time and attention to eating. That means sitting down (ideally at a table); putting away the phone or laptop; turning off the TV and giving full attention to a meal.
A bit of company is good, if you have it; eating with others has benefits both physical and psychological.
Tuning into your own body's signals can take a bit of practice. If you're someone who regularly snacks, for example, you may never feel truly hungry.
Try skipping a snack and waiting until you feel a little pang of hunger (physical hunger, not psychological craving) before eating again. When you do eat, eat slowly and stop a quarter of the way through the meal, and again half way through, to check in with yourself and see how you feel.
Towards the end of the meal, stop and imagine how it will feel to take another bite. Do you need it to feel satisfied? Or are you full enough?
If that feels too tricky, we can help ourselves to eat to 80 per cent by regulating our serving sizes to start with.
Even obvious things like using smaller plates can mean we naturally eat less, and we probably won't notice or feel deprived. We can use our brains' way of tricking us to our own advantage.