COMPONENTS OF ENERGY EXPENDITURE (CALORIES BURNED)
Energy expenditure can be thought of as Total Daily Energy Expenditure (TDEE). TDEE is the total amount of calories burned in one day. This is the calories out part of the energy balance equation.
TDEE is made up of 4 components.
- Basal Metabolic Rate (BMR)
- Thermic Effect of Food (TEF)
- Exercise Activity Thermogenesis (EAT)
- Non-Exercise Activity Thermogenesis (NEAT)
Now, these terms might look and sound confusing but I’ll break them down below so that you have a solid & practical understanding of each component.
Basal Metabolic Rate (BMR)
The minimum amount of energy / Calories required to keep your body functioning and alive at complete rest. This includes energy expended for functions such as brain function, digestion (RMR) and respiration.
Thermic Effect of Food (TEF)
The amount of energy/calories your body burns storing, absorbing and digesting food
TEF accounts for ~8-15% of TDEE
Each macronutrient (protein, carb, fat) has a different thermic effect. That is, they each require a different amount of calories for storing, absorbing and digestion.
TEF of each macronutrient
- Carbs: 5-10% of calories from carbs
- Protein: 20-30% of calories from protein
- Fat: 0-5% of calories from fat
An example: If you consumed 100 Calories of protein, 20-30 of those Calories (20-30%) will be burned just to store, absorb and digest the protein. If you consumed 100 Calories of fat, 0-5 calories (0-5%) will be burned and if you consumed 100 Calories of carbs 5-10 calories will be burned.
As you can see protein has the highest TEF, that is it requires more energy to metabolise, that is it requires the most calories for storing, absorbing and digesting. A diet higher in protein can help to (slightly) increase TDEE compared to a diet that is lower in protein. This is why you will hear that high protein diets can have a metabolic advantage.
Exercise Activity Thermogenesis (EAT)
The amount of calories burned during intentional exercise
EAT varies greatly between individuals depending on their exercise habits. In general, it can account for between 0-30% of TDEE.
The amount of calories burned during exercise will depend on the type, duration, intensity, volume and of exercise.
As you become fitter and adapted to a particular exercise your body becomes more efficient at fuelling that exercise and you will burn less calories during that exercise. For example, if someone starts running their body will become more efficient at providing energy to fuel running and less calories will be burned.
EAT is also usually a lot less than you may think.
One study found that those who exercise, do so, for less than 2 hours per week, making the contribution of EAT to TDEE negligible. EAT contributed less than 100 calories per day or 1-2% of TDEE for the week.
For the majority of people EAT will account for 0-10% of total calories burned. The upper limits of 30% are seen in endurance athletes.
So, exercise doesn’t contribute that much to total energy expenditure. This is in part why you won’t out-exercise poor nutritional habits/behaviours.
Non-Exercise Activity Thermogenesis (NEAT)
NEAT is the amount of Calories burned / energy expended during activity that is not sleeping, eating or intentional exercise e.g. hitting your daily step target, standing at your desk, gardening, walking to work, doing housework and fidgeting etc.
NEAT can account for as little as 6% to as much as 50% of TDEE depending on an individual’s activity levels. Calories burned through NEAT can vary up to 2000 calories per day between 2 individuals of similar size, depending on their activity levels.
NEAT is very important for those seeking fat loss or weight maintenance.
NEAT is the predominant component of activity thermogenesis i.e. it can contribute more to TDEE than calories burned from intentional exercise….You can burn more calories by increasing your NEAT than performing intentional exercise!
NEAT is also the most variable of the components of TDEE and can help greatly to achieve a caloric deficit or a larger caloric deficit. Therefore, it is an essential tool for fat loss and should not be overlooked.
Putting this all together. If someone is maintaining weight on 2500kcal per day the breakdown of their energy expenditure could look like this.
- TEF = 250kcal
- EAT = 125kcal
- NEAT = 625kcal
- BMR = 1500kcal
Understanding the components of energy expenditure can help you to make decisions that will help to increase total energy expenditure if fat loss is your goal.
The Role of Non-exercise Activity Thermogenesis in Human Obesity (2018) https://www.ncbi.nlm.nih.gov/books/NBK279077/