Full Lesson · Metabolism & Energy Balance
Three Sources, One Total
Three Components
BMR, TEF, and Activity
Total Energy Expenditure is the sum of three distinct sources of calorie burn: Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and Physical Activity (which includes both structured exercise and everyday movement).
BMR's Dominant Share
60-75% of TEE
BMR is typically the largest component, representing roughly 60-75% of TEE for most people — meaning the majority of daily calorie burn happens regardless of activity level.
TEF's Smaller, Consistent Share
About 10% of TEE
The Thermic Effect of Food typically represents about 10% of TEE — a relatively fixed percentage tied to how much food is eaten and its macronutrient composition, since digesting food itself requires energy.
Physical Activity
The Most Variable Share
Physical activity is by far the most variable component of TEE, ranging from as little as 15% in sedentary individuals to a much larger share in highly active people or athletes — making it the component most directly under a person's day-to-day control.
🍽️ Real Clinical Scenario
A patient trying to lose weight asks a dietitian which part of their daily calorie burn they should focus on changing.
Breaking down TEE
The dietitian explains that BMR, TEF, and physical activity together make up total daily calorie burn.
Explaining fixed vs flexible
BMR and TEF are relatively fixed based on body composition and diet composition, while physical activity is the component most within the patient's control day to day.
Setting realistic expectations
Even significant increases in exercise represent a comparatively smaller slice of TEE than BMR does, so exercise alone often has a more modest calorie impact than patients expect.
Recommending a combined approach
The dietitian suggests addressing both diet (which affects calorie intake significantly) and physical activity together, rather than relying on exercise alone to create a meaningful calorie deficit.
⚠️ Most Common Total Energy Expenditure (TEE) Mistakes
The trap is assuming exercise is the primary lever for changing total calorie burn — while activity is the most variable component, BMR's much larger share means diet changes often have a bigger overall impact on total energy balance.
✓ Quick Self-Test
Q1: What are the three components of TEE?
BMR, the Thermic Effect of Food (TEF), and Physical Activity.
Q2: What percentage of TEE does BMR typically represent?
Roughly 60-75%.
Q3: What percentage of TEE does TEF typically represent?
Roughly 10%.
Q4: Which component of TEE is the most variable between individuals?
Physical activity.
Q5: Why might exercise alone have a smaller calorie impact than expected?
Because it's a smaller share of TEE compared to BMR, which is a fixed, dominant contributor regardless of activity level.