A Calorie is a Calorie – Part II

This is a continuation of our discussion of calories – click here for Calories part I.

A calorie is a calorie. This is obviously true. Just like a dog is a dog, a dollar is a dollar, or a desk is a desk. There are many different kinds of dogs and desks but the simple statement that a dog is a dog is true.


Are all calories equally likely to cause weight gain?

However, that is not really the question we are asking. The real question we are asking is “Are all calories equally likely to cause fat gain?”

A calorie is simply a unit of energy. It is the energy released when certain foods are burned in a laboratory. Certain foods contain more, and some less. It doesn’t matter whether these foods are protein, fat or carbohydrate. We can burn them in a laboratory (or in our bodies) and determine the amount of heat released.

Some people believe that only the total daily caloric intake matters to weight gain. It does not matter whether we eat salad or ice cream, in the end they can all be reduced to calories. Hence the saying “A calorie is a calorie”.

This is a relatively new belief. Back in our grandmothers day – say around 1900’s, it was ‘common knowledge’ that obesity was caused by sweets and starchy foods (refined carbohydrates). If you wanted to lose weight you cut those out and you lost weight. Nobody, they would argue, got fat eating broccoli.

In other words, they believed that calories were not all equally likely to cause weight gain. Some foods, like sweets and breads, would cause obesity but others would not. A calories is not a calorie. In fact, they likely did not even know what a calorie was. So who is correct?

Let’s look at this equation:

Fat = Calories in – Calories out

Let’s ask the question “Does ‘Calories in’ matter?”. First, we must assume that changing ‘Calories in’ does not change ‘Calories Out’. That is, they are independent of one another. We assume that what we eat has no effect on how much caloric energy is used. We will see later that this is completely false.

If we reduce all food simply to their caloric component, then we can compare what goes in (energy) to what goes out (energy expenditure).

Let’s look at an analogous situation. Let us think about dollars instead of calories. A dollar is a dollar.

Fat Wallet = Dollars in – Dollars out


Fat Wallet

Now let’s ask the question “Does ‘Dollars in’ matter?’

Let’s suppose that I run a cookie store. I buy cookies for $1 and sell them for $2. If I sell 10 cookies, I make $10. If I sell 20 cookies, I make $20. So, obviously, in this case the “Dollars in” is important. The higher the dollars in, the more fat my wallet.

However, let’s consider another case. I buy cookies from the bakery for $1 and sell them for $1. If I sell 10 cookies, I make $0. If I sell 20 cookies, I make $0. If I sell more cookies, I don’t make any more money. So, in this case, the “Dollars in” amount is completely irrelevant.

What if I buy cookies for $1 and sell them for $0.50. If I sell 10 cookies, I lose $5. If I sell 20 cookies, I lose $10. In this case the relationship is completely opposite. The more ‘Dollars in”, the more money I lose.

It is easy to see in this example that what is ultimately important is the margin, or the amount of profit per dollar of sales. It is vitally important to know what is happening to ‘Dollars Out”, because that determines profit. Knowing “Dollars in” without knowing “Dollars Out” is not relevant. Assuming that ‘Dollars Out’ stays constant is not correct.

Now let’s apply this to obesity:

Fat = Calories in – Calories out

One of the major assumptions of the Caloric Reduction as Primary (CRaP) theory is that “Calories Out” is independent of “Calories In”. However, that is actually quite untrue. If the ‘Calories In’ is matched by an equal rise in “Calories out” (the margin is zero), then no amount of excess “Calories in” will result in fat storage. If ‘Calories In’ decreases, but is matched with a decrease in ‘Calories Out’, then no amount of reduction in caloric intake will result in weight loss.

Put another way, if you were to eat an extra 1000 calories in, but this was matched by an extra 1000 calories of energy expended this would not result in weight gain. It is possible to expend this extra energy as exercise, but it is also possible this extra energy is expended as an increase in basal metabolic rate (body heat).

For example, would it be possible to eat 5,794 calories a day and still not gain any weight? That is the question that Sam Feltham set out to answer using himself as an experimental subject. The (not so) surprising answer is that it is certainly possible. How, you may ask? As he increased his caloric intake to 5,797 calories/day, his body increased his metabolism to burn 5,794 calories per day. In this scenario he would not gain any weight (which he did not).

On the other hand, suppose we decrease our caloric intake by 1000 calories. If this causes our body to reduce our energy expenditure by 1000 calories, then no weight will be lost.


How to measure energy expenditure

We spend obsessive amounts of time considering the ‘Calories In’ part of the equation without any consideration of the ‘Calories Out’. Why? That is very simple. It is much more difficult to measure ‘Calories Out’ and therefore we make the simple and erroneous assumption that it is constant.
How to measure energy expenditure[/caption]

There are many metabolically active tissues (brain, kidneys, heart, liver) whose activity is simply very difficult to measure. For instance, suppose that your body decided to reduced the daily energy expenditure by reducing your body temperature from 36.5 to 36.0 C. How would we possibly measure that without fancy and expensive lab equipment and painstaking measurements?

What is crucial is not simply the “Calories in”, but the entire amount of “Calories in – Calories out”. How does changing one of these variables effect the other?

Furthermore, it is vitally important to know the breakdown of the ‘Calories Out’ or Energy Expenditure (EE). Is it voluntary exercise or involuntary resting metabolic rate?

If certain foods (what to eat) or dietary habits (when to eat) affect metabolic rate, then a calorie is not simply a calorie.

Are there food choices (what to eat) and food behaviors (when to eat) that will change Total Energy Expenditure (TEE)? The answer to this crucial question is yes but we have a lot of work to do before we can get to this answer.

Continue here for Calories Part III – Key Assumptions

Begin here with Calories I

Click here to watch the entire lecture: The Aetiology of Obesity 1/6 – A New Hope

2017-09-02T11:54:32-04:0011 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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Constance Penn

I would like to know if you have a comprehensive plan explaining how to fast for diabetes caontrol.
I would like the bone soup recipe plus how many calories to consume on fasting days. Or, are there even “fasting days” or is fasting done every day? How to make sure you’re getting all the nutrients you need. etc.. In other words ‘what’s the plan ‘?


Many of the handouts we use in our clinic are available under the “Patient Resources” tab. If you would like personalized advice, look under the “Join” tab. Fasting is an intensive program for diabetics since medications often need adjustment so should only be undertaken with strict medical oversight. In the IDM program, we individualize the fasting program, so there is no ‘best’ program for everybody.

Mer Mer
Mer Mer

Buy the book The Diabetes Code.


Even tho low-carb diet may be better for weight loss than low-fat, I dont believe the experiment you posted. I have read the article, but to me it seems like its a fake. Even when following low-carb diet, how the hell can one consume almost 6000 kcal daily and not gain any weight/fat? He is either really lucky and have brilliant genetics, or there is more behind it. Something we dont know about. Most probably it is a fake. Sorry, but this simply cannot be true. If your explanation is “as he increased his caloric intake to 5,797 calories/day, his… Read more »

Deb Griffith
Deb Griffith

His program is in the link. He lists everything he eats, any exercise he did, etc. Huffington post wrote about it. It is not fake.

Most people around me stuff their faces every day, all day, with carb rich foods. They are everywhere. I have been doing ADF for 7 weeks, and was losing, then stopped. As soon as I dropped my processed carbs down, even whole wheat stuff, I started losing again. Down 16 lbs.


[…] פוסט זה מוגש כשרות לאנשים שלא יכולים ו/או קשה להם לקרוא באנגלית. הזכויות על התוכן שייכות לכותב של הפוסט המקורי. את הפוסט המקורי ניתן למצוא בכתובת הזאת. […]

Abe Ramat
Abe Ramat

Doesn’t really effect your point, but just as a matter of logic, in the cookie example the the selling price amounts to the “dollars in,” (cashflow) not “dollars out” (expenditures). I think what you mean is “cookies in” vs “cookies out.” Still reading through part II of this series. I intend to make it through all the parts before long. In any event thanks for all the posts. I’m sure I will have questions once I finish reading, likely about the specifics of the endocrine pathways and related metabolic physiology, but it seems to be a lot of good material… Read more »

Abe Ramat
Abe Ramat

As I mentioned in my previous post, I will reserve judgement and final questions until I finish reading this series, though right now I am wondering how the assertion that “calories out” is variable is to be reconciled with research like this which asserts that our energy expenditures are surprisingly constant: http://www.nytimes.com/2012/08/26/opinion/sunday/debunking-the-hunter-gatherer-workout.html Studies like this one also implicate the importance of gut flora in regulating our metabolism (and possibly many other systems, such as our immunology), and indicate that typical hunter-gatherer diets (with some exceptions, including extreme northern latitude peoples such as the Inuit) do seem to be, in fact,… Read more »


The question that has cropped up in my mind is this: If eating less (i.e. fewer calories) causes the compensatory response of slowing the metabolism, then wouldn’t intermittent fasting in which one or more meals are skipped also cause the same relative slowing of metabolism since you are eating less? It seems to me if reducing calories via conventional dieting methods (eat less/move more) results in slowing of the metabolism, then reducing calories by the same amount via intermittent fasting would also cause slowing of the metabolism. It seems that one would need to avoid dropping calories if they were… Read more »

R Belldon Colme

“Calories” as a basis for any discussion about body fat has to first assume that 1. All food is reduced to energy in the body, and 2. The body runs on heat. Neither of these is a correct statement. MOST of what we eat is broken down into building blocks (think Legos), which are then used to replace our outer layer of skin every 28 days, nearly every cell in our bodies at least every 7 years, repair injuries, facilitate the work of the immune system, and countless other building and maintenance systems in the body. When I was a… Read more »


I am enjoying reading this and look very forward to reading the rest!….However, the Dollars in and Dollars out doesn’t work because you had dollars to begin with that you lost… Also the thing about broccoli analogy doesn’t work because you cannot physically eat the same AMOUNT of broccoli in calories to eat, say the same AMOUNT of calories that equals a chocolate bar. You would get much too over full and could not even eating the broccoli.