There are two main reasons a dog walks after a lad with a swollen belly: it is either he is about to stool or vomit.
This is a nasty proverb that comes with tons of lessens. This means that there is always something attached to an action and the action carried out is based on certain expected reactions like Newton postulated. If you are full remember that those behind you are either waiting for you to stretch forth your hand or waiting for your downfall (no man will praise you for nothing).
For instance, a man walking along the busy road would be greeted only by those expecting response from him. That’s if he is not “insane”.