The thermic effect of food (TEF) accounts for approximately 10% of total daily energy expenditure, with protein having the highest thermic effect (20-30% of calories consumed), followed by carbohydrate (5-10%) and fat (0-3%).

In plain English

Just digesting your food burns about 10 percent of the calories you use each day. Protein burns the most this way, more than carbs or fat.

Why it works

Digesting, absorbing, and metabolizing food requires energy. Protein has the highest thermic cost because amino acid deamination, ureagenesis, and gluconeogenesis are metabolically expensive processes.

The evidence

• Calcagno, M., Kahleova, H., Alwarith, J. et al. (2019). The Thermic Effect of Food: A Review. Journal of the American College of Nutrition.

• Ogata, H., Kobayashi, F., Hibi, M. et al. (2016). A Novel Approach to Calculating the Thermic Effect of Food in a Metabolic Chamber. Physiological Reports.

• Crovetti, R., Porrini, M., Santangelo, A. et al. (1998). The Influence of Thermic Effect of Food on Satiety. European Journal of Clinical Nutrition.

• Reed, G.W., Hill, J.O. (1996). Measuring the Thermic Effect of Food. The American Journal of Clinical Nutrition.

• Kinabo, J.L., Durnin, J.V. (1990). Thermic Effect of Food in Man: Effect of Meal Composition and Energy Content. British Journal of Nutrition.

Why we call confidence high

TEF ranges are consistently reported across multiple reviews and metabolic chamber studies spanning decades. The macronutrient-specific hierarchy (protein > carbohydrate > fat) is one of the most replicated findings in nutrition thermodynamics.

Where it applies

Healthy adults