Thermic effect of food (TEF)

The thermic effect of food (TEF) is the energy spent digesting and assimilating a meal, raising expenditure above resting levels for several hours.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 122.} It accounts for roughly 7 to 10% of total energy needs.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 122.}

The macronutrients have different processing costs: the IPTA estimates 15 to 30% of protein’s calories, 5 to 10% of carbohydrate’s and 0 to 3% of fat’s.^{2International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 465.} Norton and Baxter give protein a slightly different range, about 20 to 30 calories spent processing every 100 calories eaten, compared with 5 to 10 for carbohydrate and almost nothing for fat.^{3Norton and Baxter, The Complete Reverse Dieting Guide, p. 79.} They put alcohol at about 20%.^{3Norton and Baxter, The Complete Reverse Dieting Guide, p. 79.}

In practice

Protein’s share of daily calories is one of the main drivers of TEF, so an appropriately high protein intake moves a client toward the top of the range.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 122.} The increase in daily energy expenditure from a higher-protein diet is probably modest.^{4International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 466.}

During a diet, TEF falls because the client eats less food; per calorie eaten, it doesn’t seem to drop.^{5Norton and Baxter, The Complete Reverse Dieting Guide, p. 21.}