I am not certain about all of the causes, but since bulimia involves a negative introversion of one's bodily image, it is heavily induced and symptomatic of psychological shame and self-contempt, which is a very strong ego.

Work with the heart, including the magic of the roses. This heals emotional pains and can aid a bulimic in developing more conscious love and dignity for him or herself.

One can also use Anti-nervous and Calmative Plants in Esoteric Medicine and Practical Magic (page 110-111), praying for the elementals of the plants to reduce and remove the nervous anxieties constitutive of bulimia.

See also treatments for bulimia nervosa (Neurasthenia, nervousness, the nervous state, and neurasthenia) on page 197 of the same text.