Thermic effect of food (TEF) is the principle that some of the calories in the food you are eating are used to digest that same food. It’s usually expressed as a percentage of the calories.
Fat is 9 calories per gram and its TEF is 0-3%
Carbohydrates are 4 calories per gram and its TEF is 5-10%
Proteins are 4 calories per gram and Its TEF is 20-30%
As you can see there is quite a bit difference in calories used to digest the different macronutrients.
Do you really need to know it? Maybe. Maybe not.
Maybe it’s the nugget you need to help you to remember to eat protein.
Maybe it doesn’t make any difference to you.
However, it does play a role in overall resting metabolic rate, the amount of calories your body burns at rest, so it’s something worth knowing.
Your metabolism (100%) is a combination of:
Basal Metabolic Rate (70%) – this is the calories your body expends at rest after 12 hours of last meal, without shivering or sweating
Eating (TEF) 10%
You can see that TEF does play a role in overall energy used by the body.
TEF is one reason to eat about 3 meals per day and a snack. If you only eat one meal per day and it was the same about of calories as all of the calories you consumed over 3 meals and a snack, you’d burn fewer calories per day.