Imagine, for a second, that you could lose weight faster by simply eating the right foods.
- Your morning grapefruit slims and trims your thighs.
- Your daily lunch of canned tuna chips away at your belly fat.
- And your afternoon snack of nuts and berries keep the fat loss humming well into the night.
What a glorious life! Eat your way thin!
Unfortunately, this will only ever exist in your imagination.
The reality is no foods can directly result in fat loss.
(Some foods are more conducive to fat loss than others, but that’s not the same. More on this soon.)
“What about foods that boost your metabolism, though?” you might be thinking.
And that’s what brings us to the topic of this article: the thermic effect of food.
If only it were that simple.
The thermic effect of food does play a role in your metabolism and weight loss and weight gain, but not in the way that many people would have you believe.
That is, the foods you eat do affect your metabolism and the speed at which you lose or gain weight, but they aren’t the primary determinants.
And in this article, we’re going to break it all down.
By the end, you’re going to know what the thermic effect of food is and several science-based ways to use it to help improve your metabolism and achieve your fitness goals.
Table of Contents
The thermic effect of food (TEF) is the amount of energy required to digest and process the food you eat.
In this way, your metabolism does speed up when you eat, and the amount depends on several factors:
- The types of foods eaten.
As you can imagine, different foods cost different amounts of energy to process.
For example, the thermic effect is different for carbs, protein, and fats (protein costs the most energy to use and store, followed by carbs, followed by fats).
Studies also show that the thermic effect of highly processed foods is substantially less than their whole-food counterparts (and this is definitely one of the contributing factors to the obesity epidemic).
- How much food you eat in one sitting.
Small meals result in small increases in energy expenditure and larger meals result in larger increases.
Some people just have faster metabolisms than others (bastards!).
Now, if we left the discussion at that, you would probably walk away with the same misconception that many people have:
If different foods boost your metabolism more than others, then you can lose weight simply by eating large amounts of high-TEF foods.
Well, as much as I wish merely eating food was a viable fat loss strategy, it’s not.
And to understand why, we need to dive deeper into what really happens when you eat and how it relates to fat burning…
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When you eat food, energy expenditure rises.
In addition to that, however…
The magnitude of these effects varies based on what you eat. Some foods impair fat burning more than others and some are more efficiently stored as fat than others.
To understand why, let’s look at exactly what happens when we eat.
Digestion starts as soon as you put food into your mouth.
Enzymes in your saliva begin breaking down food as it moves toward the stomach, which takes over the process of reducing food to usable nutrients.
Next up is the small intestine, which continues to digest food into nutrients and then absorbs those nutrients into the blood.
Once the nutrients have passed through the walls of the small intestine and into the bloodstream, they need to be transported into cells for use.
And this is where the hormone insulin comes into play.
Insulin’s job is to shuttle nutrients into cells, but it also inhibits lipolysis (the breakdown of fat cells for energy) and stimulates lipogenesis (the storage of energy in fat cells). And shuttles nutrients into fat cells whose job is to, well, get fatter.
This makes sense because why should your body burn fat for energy when it has an abundance of food energy available?
That might sound bad, but realize that if your body were unable to continually replenish its fat stores, they would slowly (or quickly, depending on how active you are) shrink until you eventually died.
Now, these mechanisms are why many “gurus” vilify insulin and eating carbs (because carbs spikes insulin levels).
As insulin blunts fat burning and triggers fat storage, the basic theory is the more insulinogenic a diet is, the more it will cause weight gain.
This seems plausible at first blush, but it completely ignores the most important dimension of weight management:
Because the reality is insulin can’t make you fat. Only overeating can.
The scientific underpinnings at play here are referred to as energy balance, which is the relationship between the amounts of energy you burn and eat.
- If you eat more energy than you burn, you’re in a state of positive energy balance, and you will gain fat.
- If you eat less energy than you burn, you’re in a state of negative energy balance, and you will lose fat.
This is true regardless of the types of foods you eat.
Now, these principles don’t just apply to your diet as a whole and over time–they apply to every meal you eat.
Specifically, your body is always in one of two states in relation to food:
- A “fed” state.
In this state, your body is digesting, processing, absorbing, and storing nutrients from food you’ve eaten. This is when fat burning is blunted and fat stores are increased.
- A “fasted” state.
In this state, your body has finished processing and absorbing (and storing) food you’ve eaten. This is when it must turn to its fat stores to obtain the energy necessary to stay alive, and hence when fat stores are decreased.
In other words, your body alternates between storing and burning fat every day, which is neatly illustrated by the following graph:
Now, if you take a closer look at that graph, you can come to a few simple conclusions:
- If, over time, you store as much fat as you burn, then your total fat mass will stay the same.
- If you store more fat than you burn, then your total fat mass will increase.
- If you burn more fat than you store, then you total fat mass will decrease.
This is why energy balance is so important.
- When you eat more energy than you burn, the sum of the green portions of the graph outweigh the sum of the blue portions.
- When you eat less energy than you burn, the reverse is observed (the blue portions become greater than the green).
- And when you eat more or less the same amount of energy as you burn, the areas of the two portions are balanced.
Now, what does all this have to do with the thermic effect of food, you’re wondering?
Well, we recall that TEF contributes to overall energy expenditure, which means it slightly decreases the size of the green areas of the graph (the post-meal fat storage).
That is, TEF can contribute to weight loss by increasing the amount of energy your body burns, but the magnitude of these effects is far too small to really move the needle.
You can gain weight on a diet rich in high-TEF foods because you simply eat too much of them, and you can lose weight on a diet rich in low-TEF foods because you simply know how many calories to eat and regulate your intake of them.
This is why the entire idea of “fat-burning foods” is a myth…
Fitness blogs can write all the listicles they want about which foods burn fat and which don’t, but it’s all a bunch of humbug.
I don’t care how much celery or tuna you eat every day–it’s not going to noticeably decrease your fat stores unless you’re also in a state of negative energy balance (a calorie deficit).
And you now know why:
Food doesn’t burn fat. Energy expenditure does.
Thanks to TEF and other factors beyond the scope of this article, some foods result in less fat storage than others, but rest assured that an energy surplus results in some degree of fat gain regardless of the composition of your diet.
Now, I mentioned earlier that some foods are more conducive to weight loss than others.
That is, they’re not “fat-burning foods,” but they do help you lose weight faster.
Generally speaking, foods that are “good” for weight loss are those that are relatively low in calories but high in volume (and thus satiating).
Many also have a high TEF value as well, and that’s an added bonus.
Examples of such foods include…
- Basically all forms of protein
- Whole grains
- Seeds and nuts (they offset at least some of their energy density with their high TEF and satiety factors)
- Many types of fruits and vegetables
Simply eating these foods won’t reduce weight, but they can help you make better meal plans for losing weight.
If eating food boosts your metabolism, eating more meals should be better than fewer, then, right?
The flaw in this logic is the assumption that all meals result in more or less the same increase in energy expenditure.
The reality, though, is small meals result in a smaller, shorter metabolic spikes, and larger meals produce larger, longer lasting effects.
This is why research shows that there’s no significant difference in total energy expenditure between nibbling and gorging.
Regardless of the number of meals you eat every day, TEF-related energy expenditure balances out to more or less the same amount.
We’ve covered a lot of ground already, but I want to touch on one last subject before signing off.
And that’s the reality that while TEF isn’t terribly important in the overall scheme of losing fat the best type of diet for weight loss is highly thermogenic.
We recall that protein, carbs, and fats affect the metabolism in different ways. They have different TEF values and they are processed and stored differently.
There are several reasons for this:
- Protein and carbs have a higher thermic effect than fats, which bolsters daily energy expenditure.
- Protein and carbs are generally more filling than fats, which helps prevent overeating.
- Eating adequate protein and carbs while dieting for fat loss helps preserve lean mass, which in turn helps maintain a healthy metabolism.
The bottom line is this:
If you’re physically active, healthy, and have good insulin sensitivity, a high-protein, moderately high-carb, and moderately low-fat intake is going to be best.
(If that sounds ludicrous to you, check out this article on the big myths surrounding low-carb and high-fat dieting.)
You can’t lose fat faster by eating a grapefruit every day or adding spices to your meals.
You can, however, use the thermic effect of food to your advantage by eating a highly thermogenic diet that not only helps accelerate your weight loss but helps you preserve lean mass as well.
And practically speaking, the best way to do this is to eat a high-protein, high-carb, and moderate/low-fat diet.