In what order are macronutrients catabolized during the absorptive state?

During the absorptive state, the body is focused on utilizing the nutrients obtained from recently consumed food. This state is characterized by the presence of elevated blood glucose levels after a meal, leading to a preferential use of carbohydrates first.

Carbohydrates are broken down into glucose, which is not only the primary energy source for many cells but is also readily available for immediate use. This mobilization of glucose is essential because it helps maintain blood sugar levels and supports the energy demands of tissues, particularly the brain.

Following carbohydrates, fats become the next primary macronutrient to be catabolized. Dietary fats are emulsified and broken down into fatty acids and glycerol, which can be used for energy or stored for future use. This process occurs as cells still have an immediate supply of glucose, but those cells will begin utilizing fats to support longer-term energy needs.

Proteins are typically catabolized last during the absorptive state. This is because proteins are primarily used for building structures and tissues rather than as immediate sources of energy. The body will only break down muscle proteins for energy once the other macronutrient stores are running low.

This hierarchical utilization—carbohydrates first, followed by fats, and then proteins—aligns