Which macronutrient has the highest thermic effect of food?

The thermic effect of food (TEF) refers to the energy expenditure associated with the digestion, absorption, and metabolism of food. Among the macronutrients, proteins have the highest thermic effect. This means that the body expends more energy processing proteins compared to carbohydrates and fats.

The reasoning behind this higher energy expenditure lies in the complex structure of proteins, which are made up of amino acids. The process of breaking down proteins into their constituent amino acids requires more energy, as it involves additional metabolic steps compared to the simpler structures of carbohydrates and fats. Protein digestion and metabolism involve several enzymatic reactions and transformations that contribute to the higher caloric cost of processing protein.

In contrast, fats, while they are energy-dense, do not require as much energy for digestion and absorption. Carbohydrates also have a lower thermic effect than proteins because their structure is simpler and requires less energy to break down. Sugars, being a subtype of carbohydrate, similarly do not have a high thermic effect when compared to proteins. Thus, the nature of protein metabolism accounts for its leading position in terms of thermogenic response in the body.