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A diet based on making a bowel movement shortly after eating a meal to excrete the prior. Thus keeping a person at a consistent weight.
Person 1: Yo' Flossy.
Person 2: Sup?
Person 1: Hey man how do you stay so thin.
Person 2: The one in one out diet, I be shittin' all the time!
by Flossy May 27, 2005
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