What is the energy content of one gram of protein?

One gram of protein provides 4 calories of energy. This measurement is based on the macronutrient's contribution to energy metabolism in the body. When proteins are metabolized, they serve as a source of energy, particularly when carbohydrates and fats are not available. Each macronutrient has a specific energy yield: carbohydrates also yield 4 calories per gram, while fats provide 9 calories per gram.

Understanding the caloric content of macronutrients is crucial for anyone studying nutrition, as it helps in formulating balanced diets, calculating energy expenditure, and managing weight. Recognizing that protein contributes 4 calories per gram underscores its role as an essential component of the diet for tissue repair and muscle building, while also being an important energy source under certain conditions.