The Great Calorie Debate and the Search for the Metabolic Advantage

I’m sure you’ve heard the mantra ‘a calorie is a calorie is a calorie’. It’s used by many who dispute that there might be some sort of ‘metabolic advantage’ to the Atkins diet. Atkins believed that when you restrict carbs and replace with fat, that you could consume more calories and still lose weight.

This notion really ticks a lot of people off. Anthony Colpo, who wrote a terrific book The Great Cholesterol Con, says this about it:

There’s just one wee problem with the metabolic advantage theory of weight loss: It is complete bullshit.

Ok – so Anthony is a bit strident. Actually, I find a number of people who discuss nutrition a bit ‘over the top’ in delivering their message. These people are so sure of themselves, that there is no room for disagreement, and notions that disagree with their beliefs on nutrition need to be crushed.

Me – I’m OK with not being certain, as I have mentioned before. I keep myself humble by referring to the list of cognitive biases, and reminding myself: there’s a good chance I’m wrong.

I don’t claim to have the answers to this, and I’m not a scientist by any means. I do have questions, however, based on my so-called research.

For example, I’ve read about coconut oil. Coconut oil is comprised of what’s called medium chain tryglycerides – MCT for those of you that love acronyms.

Here’s an interesting fact from Wikipedia (‘If it says so in Wikipedia, it has to be true’):

MCTs passively diffuse from the GI tract to the portal system (longer fatty acids are absorbed into the lymphatic system) without requirement for modification like long chain fatty acids or very long chain fatty acids do. In addition MCTs do not require bile salts for digestion. Patients who have malnutrition or malabsorption syndromes are treated with MCTs because they do not require energy for absorption, utilization, or storage.

So…if I read this correctly, it takes less energy to absorb MCTs than other fats. Now, regarding energy, there’s no free lunch in this universe. If it takes less energy to absorb MCTs than other fats, doesn’t that give them a ‘metabolic advantage’? mean that not all calories are alike?

Next up is sugar. From the always fascinating Weston A. Price Foundation:

Sucrose is a disaccharide composed of 50 percent glucose and 50 percent fructose.

…Glucose is metabolized in every cell in the body but all fructose must be metabolized in the liver.

So again, we have sugar, with is half glucose and have fructose. One half is directly absorbed by the body, the other half has to go to the liver to be transformed into something we can absorb. Surely it takes more energy to take a trip to the liver and have it do work to convert the fructose, so wouldn’t it stand to reason that a calorie of fructose requires more energy to absorb than glucose?

Here’s what I think the problem is: the truth is – we have no way to measure exactly how food energy is absorbed and what energy is absorbed and what is consumed to absorb it. But we humans love to measure stuff, so we came up with a model.

We took the energy unit, a calorie (a Calorie with a capital ‘C’, or kcal to be anal about it) and used this as a yardstick.

Do you know what a Calorie really is? Again, from Wikipedia:

One food Calorie (1 kcal or 1,000 calories) is the amount of digestively available food energy (heat) that will raise the temperature of one kilogram of water one degree Celsius.

So a calorie is a unit of energy to heat a kilogram of water 1 degree Celsius. This has nothing to do with human metabolism – we aren’t as simple as a bucket of water, are we?

Well, the folks that are aching to measure this stuff aren’t that stupid, so they account for that by that phrase ‘digestively available‘.  What the heck does that mean?

The particular food being measured must be burned in a calorimeter, so that the heat released from the food can be accurately measured. This amount is used to ascertain the G.E.V. of the specified food. This number is then multiplied by, usually, 85%; which represents the loss happening during human digestion.

So – if we want to know how many calories are in that Twinkie, we can put it in a calorimeter, burn it to ashes, and measure how much heat was given off. Then we multiply by 85% to account for our body’s energy overhead to turn the Twinkie into something we can absorb.

Why 85%? I think the answer lies somewhere in the G.E.V. – an undefined acronym in the article. After some head-scratching on this one, I was led to Wilbur Olin Atwater – a fellow born in 1844 who came up with a system that tried to measure the energy in different foods. It is a  noble attempt to understand a complex process, but as the Wikipedia entry itself states:

Its use has frequently been the cause of dispute, but no real alternatives have been proposed.

So…what I see is a very complex system of adjustments and coefficients that try to measure the unmeasurable act of metabolism within a human individual – a best guess at how many calories are really in the food as opposed to how much we measure in the calorimeter.

The problem with guesses, especially when you do a lot of them, is that some are closer than others. So calculating calories for a given food is pretty much a crap-shoot – a statistically justified and rigorously measured crap-shoot, but a crap-shoot nonetheless.

Just because there’s a pile of research data and statistical analysis doesn’t mean anyone really knows with a degree of certainty  how one food might compare to another in terms of a net energy gain when you eat it.

But…it gets worse.

Let’s say you review what I’ve written above and conclude I am totally clueless and that calories are indeed a valid measure of the foods you eat. You believe that counting calories works, and you keep your little book that says this food is 47 calories per serving and that one is 98. You tally this on a little pad you tote around all day and at the end of the day you sum your numbers and come up with 1478 – just shy of your goal of 1500 calories per day.

What you have here is what I call ‘the illusion of exactitude’.

We don’t really know how many absorbable calories are in a given food item, though there’s been some painstaking calculations done to make it appear we do.

Then the manufacturer of our Twinkie doesn’t really put the thing in a bomb calorimeter – they calculate the calories from the list of ingredients and the previously derived values for each of them.

They tally that up, then create the nutrient data label that decorates our Twinkie box.

These labels themselves are more illusion. As stated here:

Because we know how many calories are in a gram of protein (4), carbohydrate (4), or fat (9), you would think you could calculate the number of calories just by knowing the amounts of these nutrients.  But if you do the math, sometimes the result doesn’t match the number of calories shown on the label.

And here, in deciphering how labels can game the system – referring to a food label for ‘fat free’ margarine that claims to have 5 calories per serving but really has 61 (scroll down past the entry on gum):

…but on a technicality they remain hidden from the consumer. A high-fat food is passed off as a low-calorie food. Isn’t this malevolently crafty? It is a very cruel joke played on people who count calories trying to lose weight.

There are other people questioning the ‘calorie is a calorie’ mantra – and my own personal experience tells me that food intake does not necessarily have a direct correlation to energy absorbed – and turned to fat on my ass. So is there a metabolic advantage in eating a certain way? My own experience on myself says yes.

Based on what I’ve seen above, calories as we normally think about them are total bunk.

Calorie-counters: you have my sympathy.

4 thoughts on “The Great Calorie Debate and the Search for the Metabolic Advantage

  1. I’ll agree that Colpo’s book the TGCC is really good. It enlightened me a lot. However, while calories do count sometimes, the type of calories is more important.

    “So…if I read this correctly, it takes less energy to absorb MCTs than other fats. Now, regarding energy, there’s no free lunch in this universe. If it takes less energy to absorb MCTs than other fats, doesn’t that give them a ‘metabolic advantage’?”

    Actually, I would think that gives them a disadvantage. The metabolic advantage as I understand it refers to the energy spend converting protein to glucose for fuel via gluconeogenesis.

    Dr. Eades had some very good posts explaining this. But, in all, it can at most account for a couple hundred calories a day.

    You could search his site for metabolic advantage.

    I know you read Taubes book, which I’m almost done with, but so far every Dr. Eades says seems to go hand in hand with that.


  2. LCC- Your link for the margarin takes one to an analysis of gum. Just FYI. Couldn’t locate the margarin link. KO

  3. Joe,

    You’re right about the coconut oil – I gotta stop doing these posts at 4am. I believe my point is still valid: not all calories are alike.


    Scroll down past the gum and check out the Promise margarine.



  4. This is great discussion but addresses only part of the issue; what the body does with calories after they are absorbed from the gut. The question rarely asked is this: what happens to all the calories that DON’T get absorbed into the bloodstream?

    For one thing, gut bacteria metabolize some of them generating heat. The amount of heat contributed to the body by intestinal flora depends on the kind of calories passing through the gut, the length of the gut, and the speed of transit.

    Every release of urine or feces into the external environment also ejects heat from the internal environment. Consuming hot or cold liquids and foods will add or subtract heat from the internal environment. These variables render the “digestively available food energy” concept more or less useless.

    For further discussion regarding what happens to unabsorbed calories, visit these web pages:

    David Brown

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