Juniper berries are supposed to be very good for diabetics, and in fact they are trying to develop commercial products from juniper berries for this reason.
The berries help to release insulin into the body, which can balance blood sugar levels. It has the bonus effect of helping a person to feel less hungry.
Although, oddly enough, some people once considered juniper berries to be an appetite stimulant.
Maybe it simply helped people to feel as hungry as they should feel.