<prompt> One patient with chronic diarrhea noticed improvement in symptoms after prolonged fasting. He is most probably suffering from:Inflammatory bowel diseaseIBSDiarrhea secondary to lactose malabsorptionEnterotoxin-induced diarrhea.  <response>: The demonstration of the effect of prolonged 24 h fasting on stool output can be very effective to differentiate osmotic and secretory diarrhea. A secretory enterotoxin-induced travelers diarrhea is not affected by prolonged fasting. Diarrhea secondary to lactose malabsorption would cease during a prolonged fast. Ref: Harrison, E-18, P-2460. 