TEF (also called diet-induced thermogenesis or DIT) is the smallest of the four TDEE components but the one with the most variation by what you actually eat. Each macronutrient has a different metabolic cost:
- Protein: ~20-30% of consumed calories spent on digestion. The largest TEF of any macro.
- Carbohydrates: ~5-10%, depending on processing and fiber content.
- Fats: ~0-3%. The lowest TEF; fat is the cheapest macro to absorb metabolically.
- Alcohol: ~10-30%, with significant individual variation.
A protein-heavy day genuinely burns more calories through TEF than a fat-heavy day at the same total intake. The effect is often overstated in marketing but is real: a 200g protein day burns roughly 100-150 more calories from TEF than a 75g protein day at the same calorie total.
TEF is partly why high-protein dieting produces slightly better fat-loss outcomes than lower-protein dieting at matched calories. The TEF effect is not the main reason — protein's satiety and muscle-preservation benefits dominate — but it adds a few percentage points to the case.
TEF also explains why "net usable calories" from protein are sometimes cited as roughly 3.2 kcal/g rather than the textbook 4 kcal/g. After deducting the metabolic cost of digestion, the energy actually available is somewhat lower than the gross caloric value. For practical calorie tracking, this distinction is small enough to ignore — the standard 4/4/9 macro math works fine.
What does NOT meaningfully affect TEF:
- Meal frequency. Eating six small meals does not produce more TEF than eating three larger meals at the same total intake. The effect is determined by total food consumed, not how it is split.
- Meal timing. Late-night eating does not have a different TEF than morning eating.
- "Negative calorie" foods. Celery, cucumber, and other low-calorie foods do not actually cost more energy to digest than they provide. The "negative calorie food" claim is a myth.