What is the primary fuel shift in infants transitioning to the neonatal state?

• A. From carbohydrates to proteins
• B. From glucose to fatty acids
• C. From fats to sugars
• D. From glucose to amino acids

Answer: (B)

In the transition to the neonatal state, the primary fuel shift involves moving from glucose utilization to the use of fatty acids. Immediately after birth, infants experience significant physiological changes, including a reduction in circulating glucose levels due to the separation from the maternal supply and the onset of independent metabolism.

During this period, the infant's body adapts to utilize stored energy sources, primarily relying on fatty acids for energy production. This shift is essential as infants are not usually able to consume food immediately after delivery. The utilization of fatty acids allows the newborn to preserve glucose for critical metabolic functions and for the brain, which relies heavily on glucose.

Choosing other options would not accurately reflect the metabolic responses of the newborn. For instance, the body does not predominantly shift from carbohydrates to proteins or from fats to sugars. Similarly, the reliance on amino acids over glucose does not characterize the immediate postnatal metabolic state. Emphasizing the shift from glucose to fatty acids highlights a crucial adaptation that supports the infant's energy needs during the transition from intrauterine to extrauterine life.