Where part of a calorie goes
Every time you eat, some energy is spent just digesting and processing the food — the thermic effect of food. It differs by macronutrient: protein takes the most (~20–30% of its calories), carbohydrates 5–10%, fat almost none (0–3%). Alcohol is wide (10–30%). Fibre isn't absorbed, so we exclude it from digestible carbs.
Keep it in proportion
- TEF is a small part of your day — about 10%. Basal metabolism is ~60–70%, activity is the rest.
- A high-protein meal vs a sugary one of the same size differ by tens of calories, not hundreds.
- These are ranges from group studies; your individual TEF isn't something a formula measures exactly.
For tracking a diet, log the full calories — your body accounts for the thermic effect itself. There's no "metabolism boost" or "negative-calorie" food here; the honest edge is small, and what decides your weight is the overall balance across the day.
FAQ
What is the thermic effect of food (TEF)?
TEF is the energy your body spends digesting and processing what you eat — roughly 10% of daily calories. It varies by macro: protein costs the most (about 20–30% of its calories), carbs 5–10%, fat 0–3%. It is real, but a small slice: your basal metabolism is ~60–70% of daily energy and activity is the rest.
Does protein "boost your metabolism"?
Not in the way marketing implies. Protein does cost more to digest, so a high-protein meal leaves slightly fewer usable calories than a sugary one of the same size — but the difference is tens of calories, not hundreds. It is a small, honest edge, not a metabolism hack.
Are there negative-calorie foods?
No. No common food takes more energy to digest than it provides — the thermic effect is a fraction of the calories, never more than them. Celery and similar foods are simply very low in calories to begin with.
Should I subtract TEF when counting calories?
No. For tracking, log the full calories — your body already accounts for the thermic effect on its own. Subtracting it yourself would double-count and understate your intake.