A form of the eating disorder, bulimia nervosa.
Bulimia is characterised by a regular, frequent pattern of binge eating followed by an attempt to prevent weight gain.
In its purging form, the bulimic individual attempts to prevent weight gain by inducing vomiting, or via laxative or diuretic abuse; the emphasis is on purging the food, rather than on compensating for the binge.
If you suspect purging bulimia, telltale signs include lengthy visits to the bathroom after meals (particularly if the taps are running), and diuretic, laxative or emetic wrappers in the dustbin.