One gram of protein provides approximately 4 calories of energy. This is a standard value used in nutrition and food labeling

. Additionally, protein has a higher thermic effect compared to fats and carbohydrates, meaning the body uses more energy to digest protein-about 1 to 2 calories are spent digesting each gram of protein

. Despite this, the gross energy content remains about 4 calories per gram. In summary:

• Protein: 4 calories per gram
• Carbohydrates: 4 calories per gram
• Fat: 9 calories per gram

This 4-calorie-per-gram figure for protein is consistent across dietary guidelines and scientific sources