How The Thermic Effect Of Food Impacts Calories You Burn
When we think of eating, it is pretty well understood that food contains energy in the form of calories.
However, what many people don’t realize is that all food actually requires energy just to digest and make use of.
So, in order to process what you eat, your body needs to expend energy above your regular Basal Metabolic Rate (BMR).
This is known as the Thermic Effect Of Food – or TEF for short.
As a general rule of thumb, it is often said that the TEF of the food we eat is about 10%.
That is to say, it requires 10% of the energy contained within the food itself, in the form of calories, for our body to store and process it.
However, in reality, different types of foods have greatly differing TEFs – largely based on their underlying macronutrient composition.
In this article, I’m going to be examining the TEFs of each of the main macronutrients, and how all of this can impact the number of calories that you burn each day.
The TEF Of Different Macronutrients
As I mentioned before, protein, fats and carbs require differing amounts of energy for our bodies to process.
Protein has the highest energy ‘cost’, requiring roughly 20-25% of its energy for processing.
This is one of the many reasons that it is often a good idea to follow a higher protein diet – since calorie for calorie, you can consume a greater amount of protein than either fats or carbs, due to the higher TEF, without putting on weight.
Carbohydrates, on the other hand, are considerably easier for the body to process than protein, only requiring about 6% of their energy for your body to make use of them.
Finally, fats are the easiest macronutrient for your body to digest and process, requiring only about 3% of their energy.
So What Does This All Mean?
Well, despite what some people like to claim, the thermic effect of food is rarely going to be a make or break factor in your diet.
As you can see, the TEF difference between fats and carbs is pretty negligible.
Basically, for every 100 calories of fat that you replace with carbs, you would burn an additional 3 calories per day.
Not really something to get all excited about.
However, protein does have a much greater energy cost than the other macronutrients, so following a higher protein diet – and thereby replacing some of your fat and carb calories with protein – will result in a greater number of calories burned per day.
For example, if you were to replace 100 calories of fat with 100 calories of protein, assuming that protein requires about 20% of its energy for digestion, you are looking at a 17% energy processing cost difference between the 2 macronutrients.
That is to say, for every 100 calories that you replaced with protein, you would burn an additional 17 of those 100 calories.
So Having A Mostly Protein Diet Is The Way Forward?
Not so fast…
While protein does have a higher TEF, it isn’t realistic or even desirable to get too many of your total daily calories from just protein.
For one, protein is expensive, and not very fun to eat on its own.
But more importantly, both carbs and fats play an important rule in your body’s functioning, even if their energy is more readily processed.
Fat is important for hormone regulation, and also helps make food taste good.
And carbs are essential as a short-term energy source for your body – helping to replenish your liver and muscle glycogen stores, and allowing you to have more productive workouts.
For most people, I would recommend that you get a reasonable percentage of your diet from protein, without going overboard.
This means getting around 30-40% of your daily calories from protein, and the rest from carbohydrates or fats.
In truth, trying to manipulate TEF to lose more weight is a bit of a fool’s errand…
You are unlikely to create a significant additional energy processing cost for your body, and it is really just going to be more trouble than it’s worth.
In the end, you are going to have a lot more success controlling your energy balance by reducing the energy IN part (eating fewer calories) than you are by trying to manipulate the energy OUT part (eating foods with a higher TEF).
Finally, it is worth mentioning that the whole negative calorie food myth is largely based around a misunderstanding of the thermic effect of food.
For a food to truly have negative calories, it would need to have a TEF of close to 100%, which the evidence simply doesn’t support, as I discuss in more detail in this article.
Do you have any questions about the thermic effect of different foods? Let us know in the comments below.