The macro nutrient least used for fuel
The Correct Answer and Explanation is:
The macronutrient least used for fuel is protein.
Explanation:
Macronutrients, which include carbohydrates, fats, and proteins, serve as the primary sources of energy (fuel) for the body. However, each of these macronutrients has different roles in metabolism and energy production.
- Carbohydrates are the body’s preferred source of energy. They are broken down into glucose, which is used directly by cells for energy. Glucose is especially important for high-intensity activities and is readily accessible for use by muscles and the brain. In times of excess, glucose is stored as glycogen in the liver and muscles for later use.
- Fats provide a more energy-dense fuel source than carbohydrates. One gram of fat yields about 9 calories, while one gram of carbohydrates yields only 4 calories. Fats are primarily used during low- to moderate-intensity activities and at rest, where the body taps into fat stores for energy. Fat is particularly crucial for prolonged activities like endurance exercise.
- Proteins, on the other hand, are primarily used for growth, repair, and maintenance of body tissues, such as muscles, skin, and enzymes. Although proteins can be broken down into amino acids and converted into glucose (via a process called gluconeogenesis), this process is less efficient and is generally used only when carbohydrates and fats are insufficient. The body typically avoids using protein for energy unless there is an extended period of fasting, starvation, or when carbohydrate and fat stores are depleted, such as during prolonged exercise without adequate fuel intake.
The body’s preference for carbohydrates and fats as energy sources means that protein is the least likely to be used for fuel under normal conditions. Instead, it is conserved for its essential structural and functional roles. Using protein for energy can also result in muscle breakdown, which is detrimental to overall health, especially over long periods. Therefore, the body strives to spare protein for these vital functions by primarily using carbohydrates and fats for fuel.