Thursday, January 11, 2007

Deconstructing Nutrition – The Thermic Effect of Food

Before I get started let me just say that this was by far the most difficult research project I have done to date.

The amount of misinformation, conflicting results, and misinterpreted data out there on this topic is amazing.

For this reason, I have had to break this topic up into three different parts


The thermic effect of food is the energy your body requires to digest, absorb and dispose of the nutrients that you eat. It is often abbreviated as TEF and is usually sited by diet gurus and fitness experts as the reasons why you should or shouldn’t eat a certain way.

Through a quick scan of the internet, I found the following claims:

  • The more often you eat, the higher your metabolic rate
  • Protein increases your metabolism by 40%

So it would make sense that eating multiple small high-protein meals would be the best way to increase your metabolism.

While this theory sounds great, let’s look at what the research has found…

Firstly, the one thing that all the papers I read agreed upon was that the number one factor that affects your TEF is the total amount of calories you eat.

Researchers have calculated TEF to be roughly 10% of your caloric intake.

Therefore, if you eat 1,000 Calories, you raise your metabolism by about 100 Calories and if you eat 10,000 Calories, you will raise your metabolism by about 1,000 Calories.

The majority of the thermic effect occurs in the first hour after eating, but depending on the size of the meal the effect can last from anywhere between 5 and 24 hours. It seems that the thermic effect will last until all the calories from your meals have been metabolized.

This leads us to the theory of eating frequent small meals.

From what I can tell, the idea that food frequency affects the amount of calories you burn is very debatable.

A few papers have found that eating one large meal has a higher thermic effect then many small meals. And a few papers have found that eating several small meals has a larger effect then one large meal. The rest have found no difference.

And to me, this makes the most sense.

If you eat 2,000 Calories, you will have to burn about 200 calories just digesting, absorbing and disposing of the nutrients you have eaten.

It does not matter whether you ate all 2,000 Calories at once, or spread them out through multiple small 500 Calorie meals. The total volume of calories remains the same and therefore so does their effect on your metabolism.

So far, the Thermic effect of food can be best summed up as –

“Eating increases your metabolism”

For the average person, eating around 2,500 Calories a day, the Thermic Effect of Food will increase your metabolism by between 200-300 Calories.

Here’s the kicker - If total calorie content is the best predictor of your TEF, it’s not as if you are going to eat an extra 5000 calories so you can burn an extra 500!

Luckily, there still may be ways to affect your metabolism through the foods you eat. In Part II I will break down the effect the different macronutrients have on your metabolism.


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