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Your body burns calories just to digest food — and protein wins big
💡 Protein costs your body far more energy to digest than carbs or fat, giving it a small built-in metabolic advantage.
Every time you eat, your body spends energy breaking food down, absorbing it, and storing it. This hidden cost is called the thermic effect of food (TEF), and it typically accounts for about 10% of your daily calorie burn. But here's the twist: not all foods charge the same digestive 'tax.'
Protein has by far the highest thermic effect — roughly 20–30% of its calories are burned just processing it. Carbohydrates cost around 5–10%, and fat only about 0–3%. So if you eat 100 calories of chicken, your body may only net around 70–80, while 100 calories of butter nets almost all 100. This is one reason higher-protein meals feel more 'metabolically active' and tend to be more filling.
This doesn't mean protein is a magic calorie-eraser — the effect is real but modest, and total intake still matters most. What it does explain is why whole, protein-rich foods stretch further than the calorie label suggests, while heavily processed, fatty foods give back almost nothing. TEF is a small, steady edge, not a shortcut.