Why the Energy Balance Theory is pseudoscience

Why the Energy Balance Theory is pseudoscience

First of all, its basis is a mere tautology (i.e. needless repetition of an idea) referred to the adipose tissue:

if the adipose tissue accumulates energy, in that tissue more energy comes in than gets out

This is just a truism, because that is what “accumulation” means, since energy can’t come out of nothing nor can it disappear, but this tautology tells us nothing about why the accumulation of triglycerides is happening. The tautology (in its correct form) is useless. The false sense of utility provided by the Energy Balance Theory comes from a deceitful transformation of the useless tautology: the trick is that the boundary for the application of the First Law of Thermodynamics is unjustifiably considered to be the whole body’s boundary, instead of the correct boundary, which is the adipose tissue’s boundary. Understanding this deception is crucial: if you want to apply the First Law of Thermodynamics, you must have a clearly defined physical boundary in its use. The Energy Balance Theory violates that principle and that fact makes this theory a hoax.

A thermodynamic system is that part of the world to which we are directing our attention. Everything that is not a part of the system constitutes the surroundings. The system and surroundings are separated by a boundary.

Internal energy is the totality of all forms of kinetic and potential energy of the system

When the “Calories In” and “Calories Out” terms are used, the physical boundary is the whole body’s boundary. This is mandatory. And, therefore, the totality of all forms of energy in the body have always to be taken into account. It is unjustifiable and deceitful to only consider the energy stored in a specific tissue (e.g. the accumulation of triglycerides in the adipocytes).

Calories In = Calories Out + Change in FAT DEPOSITS
←  WRONG

Calories In = Calories Out + Change in ALL ENERGY STORES
←  CORRECT, BUT USELESS

Any energy that’s left over after the body has used what it needs is stored as body fat (source)

That is a theory that doesn’t derive from physics’ laws.

The faux causality problem

Moreover, the Energy Balance Theory relies on an unfounded attribution of causality. It is easy to understand this point, just by comparison with any other growth in a biological system. What does the Energy Balance Theory tell us about conditions such as fatty liver, muscle hypertrophy, giantism or a tumor’s growth? What does it tell us about how anabolic steroids work? All of those situations represent the growth of tissues inside of the body, and therefore they represent energy accumulation in one or several tissues, just as obesity does.

Fatty Liver

Fat accumulates in the liver, therefore

it is an incontrovertible fact of physics that fatty liver happens when calorie intake exceeds expenditure […] the laws of physics ensure that any person will reverse its fatty liver if calorie intake is reduced sufficiently

it is an incontrovertible fact of physics that weight increases when calorie intake exceeds expenditure […] the laws of physics ensure that any obese person will lose weight if calorie intake is reduced sufficiently

Giantism

Your body can’t grow unless you eat more than you expend:

An imbalance between energy intake and energy expenditure is the primary etiology for giantism.

An imbalance between energy intake and energy expenditure is the primary etiology for excess weight gain.

Muscle mass

Muscle tissue can’t grow unless there is a caloric inbalance:

Muscle hypertrophy is defined as a state of increased muscle mass resulting from chronic nutrient excess, where energy intake significantly exceeds energy expenditure

Obesity is defined as a state of increased adiposity resulting from chronic nutrient excess, where energy intake significantly exceeds energy expenditure

Tumor

A tumor can’t grow unless more energy comes in than gets out:

A key determinant of a tumor’s growth is the balance between ingested calories and the body’s basal energy expenditure. The tumor’s growth therefore results when small positive energy balances accumulate over a long period of time

A key determinant of obesity is the balance between ingested calories and the body’s basal energy expenditure. Obesity therefore results when small positive energy balances accumulate over a long period of time

Anabolic steroids

Do anabolic steroids increase your muscle mass by making you hungry or sedentary?

if anabolic steroids don’t increase energy intake […], and don’t decrease energy expenditure, then how exactly are they supposed to cause energy accumulation in the body as fat? There is no energy fairy

if insulin doesn’t increase energy intake [… ], and doesn’t decrease energy expenditure, then how exactly is it supposed to cause energy accumulation in the body as fat? There is no energy fairy

Your energy expenditure is not a controllable input of the system

The Energy Balance Theory hoax is supported with rethorical fallacies where the energy expenditure is alluded as if it were a controllable input of the equation. It is not. If both energy intake and energy expenditure are considered inputs of the system, and if the decepcion explained above is used (i.e. considering only the energy stored in a specific tissue), a false impression of causality is created:

When calorie expenditure decreases and calorie intake increases, the energy balance equation leaves only one possible outcome: fat gain (source)

When calorie expenditure decreases and calorie intake increases, the energy balance equation leaves only one possible outcome: fatty liver or muscle hypertrophy or giantism or a tumor’s growth or you are pregnant and the fetus grows

As explained above, to assume a result for an output (“calorie expenditure decreases”) is cheating. It is not an input we can control.

When calorie intake increases, in the case where the calorie expenditure decreases the energy balance equation leaves only one possible outcome: fatty liver or muscle hypertrophy or giantism or a tumor’s growth

The energy balance equation can NEVER be used to predict the response from a living tissue to a stimulus, because that law has nothing to do with biology. Its use related to the study of obesity is based on rethorical fallacies and it is, therefore, unwarranted.

Does this mean that the First Law of Thermodynamics is not valid in a biological system?

That idea is not correct: the First Law of Thermodynamics is always fulfilled, and, therefore, it is also fulfilled in biological systems. It is the Energy Balance Theory what is a fraud, because it is both a misapplication and a misinterpretation of what the First Law of Thermodynamics says.

The pseudoscience is the pretension that the Energy Balance Theory is rightfully derived from the First Law of Thermodynamics and that, therefore, it must be used to deduce causes and solutions for obesity. The Energy Balance Theory is a hoax and it can’t be used for that purpose, just as it is clearly inappropriate to deduce how to cure your fatty liver, how to increase your muscle mass or how to treat a kid that suffers from giantism. Obesity is not a special condition.

Ultimately, obesity reflects energy imbalance, so the major areas for intervention relate to dietary intake and energy expenditure, for which the main modifiable component is physical activity (source)

Giantism also reflects energy imbalance, right? What are the major areas for intervention in that case? A tumor’s growth also reflects energy imbalance, right? What are the major areas for intervention in that case?

Further reading:

The Minnesota Starvation Study

I’m going over some aspects of The Minnesota Starvation Study, an experiment that has been commented previously in this blog (see,see,see).

“The Minnesota Starvation Study”

The objective of the experiment was to study the recovery phase from a malnutrition condition. In order to do so, first weight loss was induced by caloric restriction and physical exercise. The duration of this first phase was 6 months. After those 6 months, the researchers tested different options in the weight recovery phase.

According to the researchers, the rate of weight loss in the first phase approached zero after 24 weeks (see):

The “ideal” relation between body weight and the course of semi-starvation was believed to be that in which the rate of weight loss would change at constant rate to reach zero change at the end of 24 weeks

Mathematically, the general curve required for weight versus time is represented by a parabola with vertical axis and zero slope at 24 weeks.

Note that the researchers tell us that the body weight evolved in such a way that at week #24 there was no weight loss: “zero change”, “zero slope”.

In the picture below we can see the evolution of the body weight of the participants (white dots) and the energy intake during that period (black dots):

minesota.png

The important fact here is the participants always followed a hypocaloric diet and they stopped losing weight. They went from consuming 3150 kcal/day at the baseline to consuming about 1750 kcal/day. Taking into account only the energy intake, they applied a caloric restriction of around 1400 kcal/day:

It must be noted that the present subjects changed from a control average of 3150 Cal. to a semi-starvation average of 1755 Cal.; this represents a potential deficit of 1395 Cal. per day.

After allowing for all individual adjustments in the diet, the average individual daily intakes averaged, for successive months, 1) 1834, 2) 1833, 3) 1766, 4) 1661, 5) 1694, 6) 1764 Calories.

In short, they are living in a facility, their intake is absolutely controlled, they are eating much fewer calories than they used to, and they are also doing physical exercise (therefore, their enegy expenditure is supposed to be high) (see),

The participants were expected to walk 22 mi (35.4 km)/wk and expend 3009 kcal (12552 kJ)/d.

But after 6 months of caloric restriction, although they still have body fat they could lose, they are not losing any more weight. I want to insist on this: they are “eating a lot less” and they are not losing weight.

As I said above, the official goal of the experiment was to analyse the best way to recover from a malnutrition condition. From 6 months (time point S24 in the graph below) onwards, the energy intake was gradually increased. At time point R12, although the participants always had consumed less calories than they used to (red lines in the picture remained always below 100%), they had already recovered almost all the body fat (point marked with arrows on the solid curve) that they had previously lost.

minesota2

In this study:

  • weight loss reaches a plateau, although the caloric restriction is maintained and there is still body fat that can be lost
  • under caloric restriction conditions, body fat accumulation has been promoted and although the participants never stopped following the calorie-restricted diet, they gradually increased their body fat

magia

When you are “eating less and moving more”, but you reach a plateau, your options are: keep on following the diet and slowly regain the previously lost weight, or you can start consuming a normal amount of food and you will regain the lost weight faster.

Are we obese because of a hungry brain or are we because of the pseudoscience that the “experts” spread?

The energy balance theory

Stephan Guyenet, PhD has written a book titled “The Hungry Brain: Outsmarting the Instincts That Make Us Overeat “. Just having a look at its cover makes it clear that nothing interesting can be expected from inside the book, as this guy is trying to answer a wrong question: he assumes that the cause of obesity is that we overeat.

A couple of excerpts from the book:

Three independent methods suggest that our calorie intake increased substantially over the course of the obesity epidemic, and this increase is sufficient to account for the weight we gained. Simply stated, we gained weight because we ate more.

When you eat more calories than you burn, the excess calories are primarily shunted into your adipose tissue. Your adiposity, or body fatness, increases. It really is as simple as that

Any energy that’s left over after the body has used what it needs is stored as body fat

When calorie expenditure decreases and calorie intake increases, the energy balance equation leaves only one possible outcome: fat gain. We gained fat as we ate more calories than we needed to remain lean, given our physical activity level. In other words, we overate.

Quackery and pseudoscience

Two sentences from Guyenet’s book are perfect as an illustration of how the energy balance pseudoscience is built:

When you eat more calories than you burn, the excess calories are primarily shunted into your adipose tissue. Your adiposity, or body fatness, increases. It really is as simple as that

Any energy that’s left over after the body has used what it needs is stored as body fat

Is actually that the way our body works? First our body uses the energy it needs, and then what’s left is stored as body fat? Is that what our knowledge of the human body’s physiology says that happens? I’d like to see the scientific evidence that supports Guyenet’s claims, because I think it is absolutely UNTRUE that our body works the way he declares. Guyenet’s ideas are not science, they are quackery.

What are the tricks here?

    1. the sophistry makes energy expenditure seem like an input in the “human body” system. And once two terms of the energy balance (i.e. expenditure and intake) are fraudulently presented as inputs, then the energy balance equation is used to deduce that the the third one (energy stored as body fat) is forced to change. But the caloric intake is, actually, the only input in the “energy balance” model: energy expenditure and energy accumulation are outputs/results/consequences, not inputs/variables under our control. They deduct what is cause and what is effect from a mathematical equation when causality can only be inferred from the knowledge of how this particular system works.
    2. without any possible justification, they use the term “body fat” in the energy balance equation, instead of “energy accumulation”. The result of this is that two terms of the energy balance equation are related to the human body as a whole, but the third one (and also the conclusions) are related to a specific tissue. As I said before: unjustifiable.
    3. they perform a one-dimensional problem analysis, one that misleadingly only takes into account the “energy” variable and, logically, this approach is a blind alley in which the only conclusion that can be reached is to identify the calories as cause or solution for our obesity problem.

Moreover, the data that Guyenet is using is epidemiological, i.e. statistical data from a population. These data aren’t from a controlled experiment’s output. In this case, not even the caloric intake is necessarily an input, a cause: a priori it is only an effect, an observed symptom. Nobody here has carried out a controlled experiment in which the caloric intake has been increased: we are observing that the caloric intake has increased in the last decades, because of an unknown cause. There is no rational basis supporting Guyenet’s claims, which are the idea that two of the terms of the energy balance equation have changed and then, as a consequence, the third one has been forced to change.

An inappropriate food composition (i.e. the presence of sugars, grain flours, added chemicals, etc.) could have simultaneously induced fat accumulation —-per se, independently of the calories consumed—, an increase in the caloric intake (which in turn aggravates the body fat accumulation) and a reduction of the physical activity levels. The laws of thermodynamics can’t say what is cause and what is effect, nor do they impose a relevant role for energy, neither as a cause nor as a solution to the problem of obesity. The idea that “calories count” is not derived from the thermodynamics laws, and therefore it needs to be proved. I believe it is really significative that when evidence is presented to defend this theory, it is always false.

Although I have written repeatedly about all these sophisms, there is one of them that I consider critical:

from a tautology (i.e. saying the same in a different way) it is inferred that gaining or losing weight are energy balance issues, and that talking about calories is unavoidable.

“If you eat more calories than you burn, you will gain weight”

imagen_0508

The best way to explain the deception is, probably, to apply the same reasoning to a different tissue, e.g. muscle mass:

the laws of physics tell us that muscle mass can’t get bigger unless you eat more than you spend, so the increase in muscle mass happens as a result of a caloric intake that is excessive for your energy needs

You know it is wrong. You know that there is a “trick” in the reasoning. You know that the laws of physics don’t say that the muscle mass increases because you eat too much and move too little, and nobody can convince you of that, no matter how skilled they are playing with words. You understand that, when talking about the muscle tissue, it is absolutely stupid to use the energy balance theory to infer the cause of the growth. Once you realize that facts, nobody will ever convince you that using the laws of physics is a must when talking about the adipose tissue.

If you consume more calories than you burn, will your muscles grow?

What is wrong with the above sentence? This is not a rhetorical question: it is an important one. Can you explain the fallacy?

The carrot, the stick and the string

In one of my favourite blog posts, ““, I use the analogy of a man attached to a carrot by means of a stick and a string (see image below). What I try to to illustrate with the analogy is how solutions for a problem derived from inviolable laws of physics, can be undeniably stupid. As we will see next, a key in the fallacy is assuming a value for a parameter that is not actually under our control.

Stick

Referred to the picture above, are the following statements true or false?

If you run faster than the carrot, you’ll reach it.

If you run slower than the carrot, it will eventually disappear from your sight.

Reaching the carrot is about managing your speed relative to the carrot’s speed. Creating a speed surplus is the way to reach it, while a speed deficit will make it move away from you.

Disassembling the stick that links you to the carrot is useless, because unless your speed is greater that the carrot’s you won’t reach it.

Are you still not persuaded that speed is the key to solve the problem?

all you need is to know is the carrot’s speed and then move faster than it. Let’s say that the carrot is moving at 1 km/h. In this case, you only need to move a little faster, for example at 2 km/h, and I can guarantee that you’ll reach the carrot. It really is as simple as that.

Do you disagree with this? May be you think that it is possible to reach the carrot without being faster than it is? I’m sorry to break this to you, but that would violate the laws of physics and you can’t do that.

Is it true that if you run faster than the carrot you’re going to catch it? Yes, it is, but it is a sophism , because this solution is only correct in appearance, since it is unrelated to the specifics of the problem. Any reference made to the carrot’s speed should be making clear that this magnitude is an observed output, instead of giving the impression that it is an input with a specific value or that we can force a positive or negative difference relative to another parameter.

According to logic, what is the relationship between the man’s speed and his distance to the carrot? Does logic say that managing his speed is the way to reduce that distance? Do the laws of physics tell us that any solution that works does so simply because it helps us increase our speed?

If the laws of physics say always exactly the same thing, whether there is or there isn’t a stick that links you to the carrot, can these laws be useful in any way to solve the problem?

The laws of thermodynamics are exactly the same regardless of the physiological mechanism used by an adipocyte to grow! What on earth made us believe that these laws can be useful for understanding or curing obesity? Nobody uses them with any other growth of a tissue. Isn’t that fishy?

Summary

We are nothing else than arrogant morons. If we ask a child for help on how to reach the carrot, he/she will not say that you have to create a speed surplus. Moreover, the “speed” concept won’t even cross his/her mind. And he/she will solve the problem. The fact that a law of physics is inviolable, doesn’t mean that that law is necessary, nor useful nor relevant to solve a problem. In my opinion, the people that defend the use of the laws of thermodynamics in nutrition are themselves the problem and will never be the part of the solution.

If you consume 2000 kcal/day and your expenditure is 1950 kcal/day, you will gain weight. If you have that same energy expenditure and you consume only 1900 kcal/day, you will lose weight.

Did we gain weight because we consumed more calories than we expended? Can you tell now how, from a tautology that tells us nothing useful, has the energy balance pseudoscience been built?

Further reading:

Sugar-sweetened beverages and obesity

DAILY calories from sugar-sweetened beverages among U.S. adults (1980-2010):

imagen_0462 (source,source)

CUMULATIVE TOTAL increment in the percentage of obese adults (orange stars) versus CUMULATIVE TOTAL calories from sugar-sweetened beverages (blue line; numerical data not shown in the figure):

Are these data consistent with an important effect of sugar-sweetened beverages on body weight? Do they suggest, on the contrary, that sugar-sweetened beverages are highly unlikely to be an important cause of obesity?

Further reading:

If your today’s sugar intake is lower than yesterday’s, do you slim down?

Introduction

This article is an extension of an article that I posted a few days ago. The idea that I want to discuss is the one below:

We have data from the time evolution of two parameters, named A and B. Some people believe that there is a dependence relationship between A and B so that A has a significant effect on B, but we know that A suffered a trend change and B didn’t, so other people say that this fact suggests that it is highly unlikely that A has a significant effect on B.

For the purpose of explaining the failures in the previous idea, I will assume a very simple model of obesity: we gain 3 g of body weight for every 100 g of sugar consumed. Please, don’t bother to criticize this model: I will only use it as a tool to explain the errors in the idea explained above. What we will see is that, under the premise that sugar is determining our body weight gain, the correlation between sugar intake and body weight may be low. That is the main conclusion and the specific model used for the explanations is irrelevant.

DAILY and CUMULATIVE TOTAL parameters

As said above, our assumption is that we fatten 3 g for every 100 g of sugar consumed. If our intake of sugar were 50 g, we would fatten half that amount: 1.5 g.

imagen_0440

Given a specific sugar intake, the DAILY increase in body weight will be directly related to that DAILY sugar intake.

If I’ve consumed a certain amount of sugar PER YEAR, the PER YEAR increase in body weight would also be directly related to the PER YEAR sugar intake. For example, if one year’s sugar intake were 33 kg, our body weight would increase by 1 kg that year. Had I consumed only one third of those 33 kg, my body weight would have increased that year one third of 1 kg.

Let’s say that over the years our DAILY sugar intake has changed according to the blue curve in the graph below. In this scenario, our DAILY body weight gain would change as indicated by the red curve (calculated according to the hypothesis of that we fatten 3g per each 100 g of sugar consumed).

imagen_0441

DAILY sugar intake and DAILY body weight gain are directly related variables. Their correlation, i.e. the mathematically-computed resemblance between them, is maximum.

If we compute (in blue) the CUMULATIVE TOTAL sugar intake since 1980 (i.e. for each year we compute the total amount of sugar consumed since 1980 until that year), versus (in red) the CUMULATIVE TOTAL body weight increase since 1980 until that year, we get this:

imagen_0442

Again, as we saw with DAILY body weight increase and DAILY sugar intake, there is a direct relationship between CUMULATIVE TOTAL sugar intake and CUMULATIVE TOTAL body weight gain. This is also to be expected: under the premise that body weight gain is directly proportional to the sugar intake, if the CUMULATIVE TOTAL sugar intake over the past X years gets bigger you are expected to gain more weight, and if it gets smaller you are expected to gain less weight.

In order to clarify what comes next, let’s assume we are filling a bucket by pouring into it daily glasses of water. Every day we pour into the bucket the contents of one glass of water. Let’s assume that the volume of water in the glass has been progressively rising, day after day, until reaching a peak at 110 ml, and then, for the last 15 days we have gradually reduced the volume of water in the glass until reaching 95 ml, is the cumulative total water in the bucket expected to be reduced at the end of those 15 days? Does anyone think that if I reduce the volume of water poured daily, the volume of water in the bucket has to decrease? When we confirm it doesn’t decrease, do we conclude that it is highly unlikely that the volume of water in the glass has an important effect on the volume of water in the bucket?

Let’s get to the point, but first remember that the correlation between DAILY sugar intake and DAILY body weight gain is maximum, and remember, too, that the correlation between CUMULATIVE TOTAL sugar intake and CUMULATIVE TOTAL body weight gain is also maximum. Now, what kind of relationship exists between the DAILY sugar intake at a given year and the CUMULATIVE TOTAL body weight gain at that same year? A direct relationship is not to be expected: if the DAILY sugar intake is reduced, the CUMULATIVE TOTAL body weight is not expected to be reduced, in any case that year the body weight will go up by a smaller amount, but it will continue to increase, and the effect of a smaller DAILY sugar intake will also be small in relative terms, since we have only changed the data for one year that has to be accumulated to the rest of the years in the CUMULATIVE TOTAL: we have been accumulating body weight for years and the sugar intake during the last one of those years is expected to have a small effect in the CUMULATIVE TOTAL.

From another point of view, the CUMULATIVE TOTAL sugar intake —including the contribution from last year, but with a weight that depends on how many years are being considered—, is the variable which determines the CUMULATIVE TOTAL body weight gain to that year. It is nonsense to expect a direct relationship between DAILY sugar intake and CUMULATIVE TOTAL body weight gain. And, in fact, that relationship is not a direct one. Assuming that a man weighed 80 kg in 1980, the graph below shows his CUMULATIVE TOTAL body weight (red curve) versus his DAILY sugar intake (blue curve):

imagen_0443

We know that the red curve is completely determined by the blue curve, but they don’t have a good correlation. Or in other words, we confirm that a low correlation tell us nothing about the existence of a dependence relationship between two variables. If for the same situation, we had chosen the two previous graphs, we would have concluded that the relationship between sugar intake and body weight gain is undeniable.

If we recall the idea at the beginning of the article, A (blue curve) has changed, and the effect on B (red curve) is apparently small, but we know for a fact that A completely determines B.

What are we seeing?

In the last graph I presented above, the red curve is completely determined by the blue curve and the correlation between them is low. How is that possible? Because these two variables, while they are completely related, they don’t have a direct relationship. One variable is the CUMULATIVE TOTAL body weight gain, the effect of several years of fattening, while the other variable is just the DAILY sugar intake for one of those years. The fact that one of them goes on rising, albeit more slowly, when the other one decreases DOES NOT suggest that a cause-effect relationship between them is unlikely. The CUMULATIVE TOTAL body weight gain is not supposed to go down when the DAILY sugar intake is reduced: a “negative consumption of sugar” would be needed to produce such an effect on body weight. And, in any case, it would be the level, i.e. the fact that sugar intake is negative, what would produce a decrease in the  CUMULATIVE TOTAL body weight gain, not the change, i.e. the fact that sugar intake decreases. Even if it were possible to consume negative amounts of sugar, neither there would be a direct relationship between both variables nor a high correlation would be expected.

anyone who defends that sugar intake is a main cause of obesity and diabetes is proposing that there is a direct relationship between those variables

That’s a fallacy. The hypothesis that sugar is fattening means that the DAILY sugar intake affects the DAILY body weight gain. Nobody says that the DAILY sugar intake is directly related to the CUMULATIVE TOTAL body weight gain to that date: it is stupid to expect that when your DAILY sugar intake goes down your CUMULATIVE TOTAL body weight has to go down. This is not mathematics: it is just common sense.

Does the data presented by Guyenet in his graph suggest, as he says, that “sugar is highly unlikely to be the primary cause of obesity“? No, it does NOT suggest that. His graph is absolutely consistent with a direct effect of the DAILY sugar intake on the DAILY body weight gain: it can easily be seen that when the DAILY sugar intake was decreased, the DAILY body weight gain also decreased.

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Summary

The main Guyenet’s mistake, or the base of his attempt of deception, is that he assumes that the CUMULATIVE TOTAL body weight gain and the DAILY sugar intake are directly related, and that hypothesis is both nonsense and inconsistent with the hypothesis that he is trying to refute. No one proposes that the DAILY sugar intake has a direct relationship with the CUMULATIVE TOTAL body weight gain: this specific relationship is expected to be non-linear! Had he compared DAILY body weight gain with DAILY sugar intake, he would have found a direct relationship (consistent with the hypothesis that sugar is fattening). Had he compared CUMULATIVE TOTAL body weight gain with CUMULATIVE TOTAL sugar intake, he would have found a direct relationship (consistent with the hypothesis that sugar is fattening).

imagen_0430 imagen_0432

We have seen in this article, with help from a simple model of obesity, that although CUMULATIVE TOTAL body weight gain and DAILY sugar intake are not well correlated, that doesn’t suggest that there isn’t a causal relationship between both variables.

On the other hand, Guyenet confuses a lower intake of sugar with a negative consumption of sugar. Logic says that if sugar is fattening, reducing its consumption doesn’t make us slim down.

Endnotes

  1. When in this article I use the term “direct” what I’m saying is that when one variable goes up the other variable also goes up and that when one variable goes down the other variable also goes down. Note that a direct relationship is not necessarily one of proportionality.
  2. the data used by Guyenet as support for his hypothesis is epidemiological. This is relevant, since when part of the population chooses to decrease their sugar intake, they probably take additional measures related to improving their health, such as not eating grains/flour, not consuming processed products, cooking more at home, less frequently eating out, etc. And, in addition, those who make these decisions have not been chosen at random: they are the ones who have decided to take care of themselves, so we’re not just comparing sugar intake: we are comparing lifestyles. That is an important difference with respect to a randomized controlled trial (RCT), where participants can’t decide if they decrease their sugar intake (and perhaps its replacement by another product). In the case of a RCT that reduction is supposed to be the only difference between goups. Guyenet’s data is far from being that case.
  3. We are talking about total sugar intake, regardless of its format, regardless of when it is consumed, regardless of which products accompany it in the mouth. A lot of information is missed.
  4. We are talking about the average sugar intake of a population and the percentage of adults above a specific level of obesity. The interesting data would be to compare individualized DAILY sugar intake and DAILY body weight change, and we would want to have this data for a large number of people.
  5. Guyenet says the variation in the percentage of obese adult has been small —he even expected a decrease! — but, actually, the change has been bigger than expected from the small reduction in the DAILY sugar intake (gradually decreasing the intake from 110 g/d to 95 g/d is an average reduction of 9% relative to the baseline: it is not an 18% decrease!). May be people who have decreased their sugar intake have also taken, at the same time, other measures to improve their health, and those additional measures could be contributing to the undeniable trend change perceived from year 2000 in the percentage of obese adults.

Further reading:

Guyenet refutes the idea that sugar causes obesity

Assume that each year you gain an amount of body weight that is directly proportional to the amount of sugar you eat. Or, in other words, if you consume 100 g/d of sugar and you fatten a few kilos, if you eat 50 g/d of sugar, you fatten half that amount.

Suppose you’ve been consuming more and more sugar and you were getting fatter. Your consumption peaked at 110 g/d. Nevertheless, in the last 15 years your consumption has gone down progressively, and today you are eating a little less than you used to: 95 g/d. What is the expected evolution for your body weight? Under the assumption that sugar is making you fatten, your body weight is expected to go on rising, but at a slightly lower rate.

That is what I show in the graph below, created assuming that fattening is directly proportional to sugar intake. The blue curve represents sugar consumption (grams/day); the stars show what the body weight would have been in case we hadn’t changed the sugar consumption trend 15 years ago; the orange curve shows the actual body weight evolution (assuming that instead of consuming more and more sugar, we have progressively and slightly reduced our consumption in the last 15 years, as indicated by the blue curve):

sgen

Again, if sugar is fattening, what effect would be expected if our consumption were reduced? We would keep getting fatter, but at a slightly lower rate. That is what the orange curve in the graph above confirmed.

A few days ago (see) Stephan Guyenet, PhD wrote an article trying to refute the idea that sugar is fattening us. In his view, the explanation is simpler than that: we eat too much unhealthy food because we like it. His is just another version of the pseudoscientific energy balance theory.

One of the arguments presented by Guyenet is that added sugar intake has declined between 1999 and 2013, but the percentage of adult obese has not. He says, those facts make “highly unlikely” that sugar is the primary cause of obesity. This is the graph he uses as proof:

His reasoning is that if consuming 110 g/d of sugar makes us fatten, consuming between 95 and 110 g/d should make us lose weight! Since epidemiological data says we kept getting fatter and fatter, he concludes that  sugar is “highly unlikely to be the primary cause of obesity”.

Americans have been reining in our sugar intake for more than fourteen years, and not only has it failed to slim us down, it hasn’t even stopped us from gaining additional weight. This suggests that sugar is highly unlikely to be the primary cause of obesity or diabetes in the United States, although again it doesn’t exonerate sugar.

What he is saying is that if hitting your head against the wall ten times produces pain, hitting your head against the wall only nine times shouldn’t be less painful, it should be pleasant. If you realise it is not pleasant, if you realise nine times is still painful, albeit to a lesser extent than doing the same ten times, this suggests that there is no relationship between the hitting against the wall and the pain you suffer. Extremely stupid reasoning.

Moreover: between 1980 and 1999, sugar consumption was in the 85 to 110g/d range and people gained weight. Guyenet says that between 2000 and 2013, when sugar consumption was between 95 and 110 g/d, body weight should have decreased.

On the other hand, note that Guyenet interprets data from the graph as if it were a controlled experiment, when it is just observational data. No controlled experiment was carried out.

Note also that the y-axis for the blue curve in Guyenet’s graph doesn’t begin with zero g/d, and this makes the decrease in sugar intake seem greater than it actually is.

Edit (1/18/2017): there is a second part of this article, providing a more thorough explanation:
If your today’s sugar intake is lower than yesterday’s, do you slim down?

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Further reading: