Which macronutrient has the highest thermic effect of food (TEF)?

Protein is the macronutrient with the highest thermic effect of food (TEF) because it requires more energy for digestion, absorption, and metabolism compared to carbohydrates and fats. When protein is consumed, the body utilizes energy to break down the complex protein molecules into amino acids, which involves several biochemical processes. This process can account for approximately 20-30% of the energy content of the protein consumed, indicating that a significant amount of calories is burned during the digestion of protein.

In contrast, carbohydrates and fats have lower thermic effects, typically around 5-10% and 0-3%, respectively, meaning they require less energy for processing. While fiber is beneficial for digestion and can help in regulating appetite and blood sugar levels, it is not considered a macronutrient in the same way that protein, carbohydrates, and fats are, and its thermic effect is also lower than that of protein. Thus, protein stands out as the macronutrient with the highest TEF, emphasizing its role in not only providing essential amino acids but also in supporting overall metabolic health.