When you begin to exercise, which stored fuel does your body typically use first to generate energy?

• A. Fatty acids
• B. Glycogen
• C. Nucleic acids
• D. Proteins

Answer: (B)

Verified step by step guidance

1. Understand the context: When you begin to exercise, your body needs a quick source of energy to fuel muscle activity. Stored fuels in the body include glycogen, fatty acids, proteins, and nucleic acids.
2. Recall the hierarchy of energy utilization: Glycogen is the primary stored carbohydrate in muscles and the liver. It is broken down into glucose, which is rapidly metabolized to produce ATP, the energy currency of the cell.
3. Learn why glycogen is used first: Glycogen is readily accessible and can be quickly mobilized during short-term, high-intensity exercise. Fatty acids, while energy-rich, require more time and oxygen to be metabolized, making them less suitable for immediate energy needs.
4. Understand why proteins and nucleic acids are not primary energy sources: Proteins are primarily used for building and repairing tissues, and nucleic acids are involved in genetic information storage and transfer. These are not efficient sources of energy during exercise.
5. Conclude the process: Glycogen is the stored fuel that your body typically uses first to generate energy during the initial stages of exercise, especially when the demand for energy is immediate and oxygen availability may be limited.