The factors affecting Total Energy Expenditure (TEE) are the fundamental components that make up the body's daily energy expenditure.
According to the reference from NCBI, TEE includes three core components:
- Resting Metabolic Rate (RMR) or Resting Energy Expenditure (REE)
- Thermic Effect of Food (TEF), also referred to as Diet-Induced Thermogenesis (DIT)
- Physical Activity
These three components collectively determine how many calories a person burns throughout the day.
The Three Core Components of TEE
Let's delve deeper into each of these factors.
Resting Metabolic Rate (RMR) / Resting Energy Expenditure (REE)
This is the energy your body needs to maintain basic functions while at rest. Think of it as the energy required just to stay alive – breathing, blood circulation, brain function, and cellular processes. It's typically the largest component of TEE, often accounting for 60-75% of daily energy expenditure.
Factors influencing RMR/REE include:
- Age: RMR generally decreases with age.
- Sex: Men typically have higher RMRs than women due to differences in body composition.
- Body Composition: Individuals with more lean muscle mass tend to have higher RMRs than those with higher body fat.
- Body Size: Taller, heavier individuals generally have higher RMRs.
- Genetics: Individual genetic makeup can influence RMR.
- Hormonal Status: Hormones like thyroid hormones significantly impact RMR.
- Fever or Illness: These can temporarily increase RMR.
Thermic Effect of Food (TEF) / Diet-Induced Thermogenesis (DIT)
TEF is the energy expended by the body to digest, absorb, metabolize, and store nutrients from the food you eat. It's the "cost" of processing food. The reference notes that TEF is also known as Diet-Induced Thermogenesis (DIT). This component usually accounts for about 10% of total energy expenditure, but it can vary based on the macronutrient composition of the meal.
- Protein: Has the highest TEF (20-30% of ingested energy).
- Carbohydrates: Have a moderate TEF (5-10%).
- Fats: Have the lowest TEF (0-3%).
Eating a meal requires energy expenditure, contributing to TEE.
Physical Activity
This is the most variable component of TEE and includes all energy expended during movement. It encompasses planned exercise (like running or weightlifting) as well as non-exercise activity thermogenesis (NEAT), which includes activities like walking, fidgeting, standing, and doing household chores.
Factors influencing energy expenditure from physical activity include:
- Duration: How long the activity lasts.
- Intensity: How hard the body is working.
- Type of Activity: Different activities burn different amounts of calories.
- Body Weight: Heavier individuals generally burn more calories performing the same activity.
Summary Table
Here's a quick summary of the main components contributing to TEE:
| Component | Description | Typical Contribution to TEE | Also Known As |
|---|---|---|---|
| Resting Metabolic Rate (RMR) | Energy needed for basic life functions at rest. | 60-75% | Resting Energy Expenditure (REE) |
| Thermic Effect of Food (TEF) | Energy used to digest, absorb, and metabolize food. | ~10% | Diet-Induced Thermogenesis (DIT) |
| Physical Activity | Energy used during all types of movement, from exercise to fidgeting. | 15-30% (highly variable) | - |
Understanding these three factors is crucial for managing energy balance, whether for weight maintenance, gain, or loss. The total daily energy expenditure is the sum of these three components.
