Explanation
In Japan, refusing food offered by a host, especially during a family meeting, is considered impolite because it implies rejection of the host's generosity and effort. It is customary to accept at least a small portion, even if you are not hungry, to show gratitude and maintain harmony (wa).
Local Tip
If you cannot eat something, take a small amount and leave it on your plate, or politely say 'okini' (thank you) and take a tiny bite to show appreciation.
How it compares elsewhere
Refusing food is often seen as rejecting hospitality; it's better to accept a small portion.
Refusing food from a host, especially at a family meal, can be taken as a personal insult.
It is generally acceptable to politely decline food if you are full or have dietary restrictions, though some hosts may insist.