Are proteins generally a major fuel source in the body?

Proteins are generally not considered a major fuel source for the body under normal circumstances. Instead, carbohydrates and fats serve as the primary sources of energy. The body's preferential use of carbohydrates and fats for energy allows proteins to fulfill their more critical roles in growth, repair, and maintenance of tissues, as well as in the production of enzymes and hormones.

While proteins can be utilized for energy during prolonged fasting or in circumstances where carbohydrate stores are low, this is not the typical scenario for energy metabolism. Therefore, protein's role as a fuel source is more supplementary, emphasizing its importance in various physiological functions rather than in energy provision during regular activities. This understanding clarifies why it is accurate to state that proteins usually are not a major source of fuel for the body.