When fasting, how does the body produce sources of energy for cells?

During fasting, the body undergoes metabolic adaptations to maintain energy levels for cells in the absence of food intake. The correct answer illustrates the body's ability to efficiently utilize different macronutrients during this state.

When fasting, the body's glucose stores become depleted. To make up for this, the body turns to protein and fat as alternative sources of energy. Proteins can be broken down into amino acids, which are then converted into glucose through a process called gluconeogenesis. This is essential for supplying energy to cells that rely heavily on glucose, such as red blood cells and certain parts of the brain.

Simultaneously, the body breaks down fats into fatty acids. These fatty acids are then transformed into ketone bodies through a process called ketogenesis. Ketone bodies serve as an alternative energy source, particularly for the brain, when glucose availability is low. This dual process enables the body to effectively manage energy needs during periods without food consumption.

In contrast, some of the other options are limited in scope. The option stating "only through carbohydrates" overlooks the body's utilization of fats and proteins. The choice that indicates "turns fats into glucose" inaccurately suggests that fats convert directly into glucose, which does not occur; rather, fats can be