7.2 Energy Expenditure: Where Your Calories Go
Understanding where your body spends its energy is essential for making sense of energy balance. Your Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day. It is composed of several distinct components, which can be grouped into two categories.
Resting Energy Expenditure (REE)
Basal Metabolic Rate (BMR) is the energy your body needs just to stay alive: maintaining core temperature, pumping blood, breathing, running your brain, and keeping all your organs functional. If you lay perfectly still in a temperature-controlled room all day, you would still burn this amount. BMR typically accounts for approximately 60% of total daily energy expenditure and is largely determined by your body size, lean mass, age, and sex [1].
Non-Resting Energy Expenditure (NREE)
Everything above BMR falls into this category:
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Thermic Effect of Food (TEF): The energy cost of digesting, absorbing, and storing the nutrients you eat. This typically accounts for about 10% of TDEE. Crucially, TEF varies by macronutrient: protein costs the most to process (20–30% of its energy content), carbohydrate is moderate (5–10%), and fat is cheapest (0–3%) [2]. This is one of the reasons high-protein diets are advantageous during a cut—you “waste” more energy just processing the food.
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Exercise Activity Thermogenesis (EAT): The calories you burn during intentional, structured exercise—your gym sessions, runs, or sports. For most people who train 3–5 times per week, EAT accounts for roughly 5% of TDEE. This number is much smaller than most people think.
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Non-Exercise Activity Thermogenesis (NEAT): Everything else—fidgeting, walking to the car, cooking, standing at your desk, tapping your foot, even the energy cost of maintaining your posture. NEAT is the most variable component of energy expenditure and can differ by up to 2,000 kcal per day between two people of the same size [3]. When you diet, NEAT drops subconsciously—you move less, fidget less, and take fewer spontaneous steps. This is a major component of so-called “metabolic adaptation.”
Putting It Together
| Component | Abbreviation | Typical % of TDEE |
|---|---|---|
| Basal Metabolic Rate | BMR | ~60% |
| Thermic Effect of Food | TEF | ~10% |
| Exercise Activity Thermogenesis | EAT | ~5% |
| Non-Exercise Activity Thermogenesis | NEAT | ~15–25% |
TDEE = REE (BMR) + NREE (TEF + EAT + NEAT)
The practical implication is clear: your gym sessions, despite feeling exhausting, contribute only a small fraction of your daily burn. NEAT—the spontaneous movement you do outside the gym—matters far more for total expenditure. If your goal is fat loss, staying generally active throughout the day (walking, taking stairs, not sitting for hours on end) is at least as important as adding another set of leg extensions.