The CICO Theory, a pseudoscience based on rhetorical tricks

(Spanish language version: click here)

The main goal of this article is to explain that the Energy Balance theory (also known as the CICO Theory) is wrong. It is important to understand that this is so, because otherwise we will continue trying to prevent or reverse our weight problems with principles that have no real basis. These wrong ideas are:

  • The cause of gaining weight is a caloric surplus.
  • The obvious solution for excess weight is to eat less and move more. Without a caloric deficit you can’t lose weight.

Yes, both ideas are wrong, fraudulent and fallacious.

I will focus the explanations on two key concepts:

  • The CICO Theory is not the First Law of Thermodynamics
  • The CICO Theory is based on unjustified premises

The First Law of Thermodynamics

Principle of energy conservation applied on the physical limits of our body (our skin):


Nobody here denies that this law is fufilled in the human body. I repeat this point: nobody here denies the fulfillment of this law.

The CICO Theory

The CICO theory is based on two unjustified assumptions:

  1. Only the energy stored in the adipose tissue is allowed to change.
  2. The adipose tissue is passive: the amount of triglycerides stored in this tissue can not change by itself (i.e. in response to physiological stimuli, such as the hormonal environment).

In the figure below, those terms with a green circle are allowed to change by themselves. The CICO Theory does not allow the third term, the one with the red circle, to change by itself.


Why cannot a food product, such as sugar, directly affect term #3? Why cannot a food product be «fattening», by itself, regardless of the calories consumed/spent? The answer is that the CICO Theory does not allow this to happen, because one of its unjustified premises is that it cannot happen. For no reason: it is just not allowed.

«Caloric excess» and «caloric deficit»

This terms imply that that there is a difference between the first two terms (the two terms with the green circle), and that difference, by means of the energy balance equation, forces a change in the third term (the one with the red circle). Note that the third term changes because the other two terms change: it is an unwarranted behavior of our body created by the unjustified premise that the adipose tissue is passive.

Note that under the unjustified premises of the CICO Theory, any solution to obesity will always be based on managing the energy intake and the energy expenditure, that is, acting on the two terms with the green circle in the figure above.

For example, when weight loss stalls, some of the defenders of this pseudoscience attribute the stall to the fact that there is a «slowing down of the metabolism». What is a slowdown of the metabolism? A change in the second term of the equation. Or they say that you are lying and you eat more food than you say. In this case, they are talking about the first term of the equation. These diagnosis and solutions respect the unjustified premise that only the first two terms of the equation have the capacity to change by themselves. Why can’t be the cause of the plateau that the adipose tissue has the drive to store fat? It can’t be because the CICO Theory doesn’t allow this possibility.

Note that if we follow the CICO logic, if the weight loss stalls because the metabolism slows down, the only possible solution is that you have to eat even less. No solution will ever be based on understanding the adipose tissue’s physiology, because the CICO Theory says its physiology is non-existent.

And that «eating less» has to work, because that metabolism slowdown «is not that big». As I said at the beginning: understanding that the CICO Theory is a hoax is key to understand that almost everything we think we know about what to do to lose weight or not gain it, is unfounded.

As a key idea: the CICO Theory does not violate the First Law of Thermodynamics, but it is not the First Law of Thermodynamics. This theory assumes a behavior of the human body that does not legitimately derive from the laws of physics, although it does not violate them.

How relevant is that the CICO Theory is based on unwarranted premises?

I will answer that question by proposing an alternative theory to the CICO Theory. This alternative theory is also compatible with the First Law of Thermodynamics. It is utterly irrelevant if this alternative is correct. What really matters is that it is possible, which

  1. makes it clear that the CICO Theory is a fraud, and
  2. helps to understand that ideas totally opposed to the CICO Theory could be the key to managing our body weight.


In this model we allow the adipose tissue to change by itself, but now the energy expenditure can’t. An unjustified premise? Exactly! A premise as unjustified as in the CICO Theory. This is precisely what I want to convey with this article.

If the adipose tissue can vary by itself, to control its size or changes we need to understand what causes fatty acids to enter or leave it: what hormones are involved, what are the physiological factors that alter those processes, etc.

Under this premise, in order to control our body weight we have to pay attention to everything that the CICO Theory considers, with no good reason, irrelevant in the processes of gaining and losing weight.

In this model a food can be fattening per se.

In this model, if the weight loss stalls, the cause lies in the adipose tissue itself, which has decided not to continue reducing its size, perhaps in response to a lack of food that our body sees as a threat to survival.

In this model the plateau has nothing to do with a «slowdown of the metabolism», which in any case would be a symptom, not the cause of the weight loss stall.

On the other hand, remember that there is a second unjustified premise in the CICO Theory: «only the energy stored in the adipose tissue can change«. Is that premise relevant? It obviously is.

We see this point clearly if, instead of imposing that only the energy stored in the adipose tissue can change, we impose that only the energy stored in a tumor can change:


Is a «caloric excess» the obvious cause of a tumor growth? Is establishing a «caloric deficit» the obvious solution to reduce its size? We know that these questions are nonsense, and they are for two reasons:

  1. The energy balance of the whole body has nothing to do with the change in the energy stored in a specific tissue: there is no justification for assuming that only the energy stored in the tumor can change.
  2. We know that the tumor does not grow nor it is reduced by the establishment of a «caloric surplus/deficit». We know that the tumor takes the initiative to grow/decrease, and we know that there is no justification for assuming that its role in its own growth is passive.

Are relevant the tricks on which the CICO Theory is based? We have seen that for sure they are.

Please note that the CICO Theory can be complex, but the complexity is only allowed in 2 of the 3 terms of the energy balance equation. A complex CICO Theory is still pseudoscience.


The CICO Theory is not the First Law of Thermodynamics.

The CICO Theory is based on unjustified premises.

A «caloric surplus» is NOT the obvious cause of obesity.

A «caloric deficit» is NOT the obvious solution to obesity.

Thinking about the effects of what we eat in our adipose tissue is not charlatanism nor it is a denial of the fulfillment of any law of physics, although it does indeed mean denying the correctness of the CICO Theory.

We have to be aware of the trap: we want to continue talking about calories, because the CICO Theory allows us to eat whatever we want, be it real food or be it an edible product. We want that theory to be correct. And the food and diet industries take advantage of that desire. But the CICO Theory is not a correct theory. And it does not work in practice either.

  1. Vicente

    Excess calories are the cause of obesity only when you believe that the CICO theory is a law of physics. It is not.

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