I Keep an industrial supply of tinned Mushy peas around, its mostly undigestable, so few calories - although prepare for mega constipation if you dont drink enough.

mind, its not unusual for me to eat about a kilo of mushy peas- then spend the next 12 hours feeling like i've swallowed a large rock- its like being punched repeatedly in the stomach-colon.

still, even if you eat a kilo, its still only a few hundred calories- little sugar, and almost no fat