The average healthy adult typically takes between 24 and 72 hours to digest food. In the first 6 to 8 hours, food passes through the stomach and small intestine. The large intestine then removes residual nutrients and water. The undigested food residue starts to exit the large intestine as waste after about 24 hours, but the complete elimination of all the food residue might take several days.
Relative Digestion Speeds
Different types of food have varying digestion times. Carbohydrates pass through the stomach and into the small intestine the quickest. Protein stays in the stomach longer than carbohydrates, but fats stay there the longest. So if your meal consists mostly of carbohydrates, the food likely will head into the small intestine, where nutrients are removed, more quickly than a meal that contains mostly proteins and fats.
Sugars and Starches
Your body converts sugars and starches, which are carbohydrates, into glucose, or blood sugar, which supplies energy to your body. The glycemic index compares the impact and speed with which different carbohydrates affect your blood glucose levels in comparison to pure glucose. For example, starches that come from white bread or french fries increase your blood sugar level nearly as quickly as pure glucose.
Foods that are high in sugars and starches, such as white pasta and refined breakfast cereal, are digested relatively quickly and have a profound effect on your blood glucose level. Foods that are high in fiber, such as fruits and bran cereals, take longer to digest and have a relatively small effect on your blood glucose level.
A rapid increase in blood sugar levels can lead to a brief energy boost soon after you eat a sugary product, but the high will wear off quickly and leave you feeling more tired than before, according to a study cited in the October 2008 issue of “Health” magazine. Although a quick snack made of a combination of protein and carbohydrates might take longer to digest, it provides a longer-lasting boost of energy without the subsequent crash. For example, try peanut butter spread on apple slices or trail mix that includes nuts and dried fruit.
- MayoClinic.com; Digestion: How Long Does It Take?; August 2010
- National Digestive Diseases Information Clearinghouse; Your Digestive System and How It Works; April 2008
- Harvard School of Public Health: Carbohydrates: Good Carbs Guide the Way
- Harvard School of Public Health: Carbohydrates and the Glycemic Load
- “Health” Magazine; Caffeine and Sugar: Why These Energy Boosters Are Poor Substitutes for Sleep; Gail Belsky; October 2008
- Photos.com/AbleStock.com/Getty Images
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.