NANP Board Practice Exam

How can the brain adapt during periods of starvation?

1. By utilizing fatty acids

2. By using amino acids directly

3. By using more ketone bodies

4. By reducing metabolic activity

The correct answer is: By using more ketone bodies

During periods of starvation, the brain adapts primarily by using more ketone bodies as an alternative energy source. Normally, the brain relies heavily on glucose for energy. However, during starvation, glucose availability decreases due to depleted glycogen stores, prompting the body to shift its metabolic processes. As fat stores become mobilized, fatty acids are released into the bloodstream. The liver converts these fatty acids into ketone bodies through a process called ketogenesis. These keto compounds, particularly β-hydroxybutyrate and acetoacetate, can cross the blood-brain barrier and serve as an efficient fuel source for the brain when glucose is scarce. This adaptation is crucial because the brain requires a continuous supply of energy to function properly. Relying on ketone bodies allows the brain to sustain its metabolic activities without the normal glucose intake, helping to preserve muscle protein by minimizing the need to break down amino acids for gluconeogenesis. While the other options may involve some impact during starvation, they do not serve as primary pathways for energy during the brain's adaptation to fasting. Fatty acids cannot be used directly by the brain due to their inability to cross the blood-brain barrier efficiently. Amino acids can be utilized, but this typically occurs later in