What is the Difference Between Absorptive and Postabsorptive State?

The absorptive and postabsorptive states are two distinct metabolic states that occur in the body during the digestion and absorption of nutrients. Here are the main differences between the two states:

Absorptive State:

Occurs immediately after ingestion of food.
Involves the digestion of food and absorption of nutrients into the bloodstream.
The body processes glucose, fats, and proteins, absorbing them across the intestinal membrane and entering the bloodstream and lymphatic system.
Excess nutrients are stored for later use, such as glycogen in the liver and muscle cells, or as fat in adipose tissue.
The pancreas releases insulin to stimulate the uptake of glucose by hepatocytes in the liver, muscle cells, and adipose tissue.

Postabsorptive State:

Occurs after the complete absorption of nutrients.
Also referred to as the fasting state, this phase happens when the body is no longer receiving energy from food.
The body switches to using stored energy reserves, such as glycogen, fat, and proteins.
During this state, the liver produces glucose to maintain blood glucose concentrations through the degradation of glycogen (glycogenolysis) and the production of ketones from fatty acids.
The pancreas releases glucagon, a hormone that stimulates the release of glucose from the liver, to maintain blood sugar levels.

In summary, the absorptive state is responsible for digesting and absorbing nutrients from food, while the postabsorptive state focuses on utilizing stored energy reserves when food is not available. These states play a crucial role in energy maintenance and overall metabolism.

On this page

What is the Difference Between Absorptive and Postabsorptive State?

Comparative Table: Absorptive vs Postabsorptive State

Here is a table comparing the absorptive and postabsorptive states:

Feature	Absorptive State	Postabsorptive State
Definition	The absorptive state, also known as the fed state, occurs after a meal when the body is digesting food and absorbing nutrients into the bloodstream.	The postabsorptive state, also known as the fasting state, occurs when the food has been digested, absorbed, and stored. This typically happens after the absorptive state or during periods of fasting.
Energy Source	Energy comes from the recently ingested food, and nutrients are absorbed into the bloodstream.	The body relies on energy reserves, such as glycogen, fats, and proteins, to provide energy during this state.
Metabolic Processes	Anabolic processes, such as the storage of glycogen and the synthesis of fat and protein, predominate during this state.	Catabolic processes, such as the breakdown of stored glycogen, fats, and proteins, predominate during this state.
Ketone Production	Ketones may be synthesized from fatty acids and triglycerides if excess acetyl CoA is generated during fat breakdown.	Ketones are more likely to be produced during the postabsorptive state as the body breaks down stored fat into fatty acids, which are then converted into ketones.
Duration	This state typically lasts for a few hours after ingesting food.	This state can last for extended periods, such as during overnight fasting or skipping meals.

In summary, the absorptive state is characterized by the digestion and absorption of nutrients from recently ingested food, while the postabsorptive state occurs when the body relies on energy reserves for fuel after digestion and absorption have ceased.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.