How does your body digest food?
How long does it take to digest food — from the time you eat it to the time you excrete it in urine or stool?
What does your liver do?
What does the pancreas do?

 Digestion time varies depending on the individual. For most healthy adults, it's usually between 24 and 72 hours. After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine. Food then enters your large intestine (colon) for further digestion and absorption of water. Elimination of undigested food residue through the large intestine usually begins after a total of 24 hours. Complete elimination from the body may take several days. 


http://www.mayoclinic.com/health/digestive-system/AN00896