so generally, food leaves the stomach about four hours after you eat it. it really depends on how big of a meal you've eaten, because the duodenum can only take in a small amount at a time for calorie absorption (i believe, on average, every 30 minutes or so it opens up to take in another handful of chyme). but, of course, digestion continues after food leaves the stomach. it goes on to the rest of the small intestine for further nutrient absorbtion, and then to the large intestine for water absorbtion. under normal circumstances, it can take 24-48 hours for a meal to fully leave your body.