The short-term effect of a diet may have nothing to do with its long-term effect (1 of 2)

(Versión en español: pinchar aquí)

One of the main dogmas of the energy balance pseudo-science is that when two diets have the same amount of calories and the same amount of protein, in that case they are equal for the control of our body weight (example). We are told that this idea derives from the First Law of Thermodynamics and that, therefore, to deny this dogma is to deny unbreakable laws of physics.

Let’s imagine that we do an experiment in which two groups of people are given much more food for a week than they would normally consume. Both groups receive the same amount of calories: one group receives 50% extra food in the form of carbohydrates and the other group 50% extra food in the form of fat. The same energy intake and the same percentage of protein. On the 7th day we measure how much body fat these two groups of people have gained that day. Should we get the same result from both dietary groups?

Is it possible, according to the energy balance pseudo-science, a result like the one I show in the graph below, where one of the diets produces more body fat accumulation than the other one?

No. It would not be possible according to that theory. This result would be in contradiction with the idea that our body weight is determined by the calories of the diet: the two dietary groups ingested the same amount of food in terms of calories!

How would the energy balance pseudo-science explain this result? It could not explain it and the reason is that that theory is nothing but charlatanism.

It is a real result, obtained from the following article.

Fat and carbohydrate overfeeding in humans: different effects on energy storage

For 14 days, 9 lean people and 7 obese people are given 50% more calories than the amount that is considered necessary for each participant. Each participant receives two types of extra food: one based on carbohydrates and one based on fat. The authors do not give details about the base diet nor about what the composition of the excess food is.

The evolution with time of the fat balance (difference between fat that is ingested and fat that is oxidized) is very interesting. Very interesting indeed.


As we can see, the result of this experiment shows that in those participants in the very first first days the “extra” dietary fat is much more fattening than the “extra” carbohydrates. But can we forecast, based on the previous figure, what will happen after day #14 (which is the day this experiment ends)?

It is impossible to ignore what we see in the figure above: not only the outcome is not determined by the calories of the diet —which is what the CICO theory postulates as obvious—in those participants (the result is a function of the composition of the diet), but we also found that it is irrelevant to know what happens in the first few days to know what will happen in the long term. We see what happens in the first 14 days of the experiment and we have no idea how the accumulation of fat would evolve from that moment on. We do not even know in what type of participants a diet can be more fattening than the other one in the long term.

The authors of the article apparently saw it differently:

we found that for equivalent amounts of excess energy, fat leads to more body fat accumulation than does carbohydrate.

Please note that they confirm that the CICO theory is dead.

But what I am most interested in is that this is a very short-term result, for all-male participants, for participants that are used to follow a high-carbohydrate diet and that are forced to eat a lot of extra food, extra food that is based on food products with a single macronutrient, not natural foods, etc. It seems to me that some people have serious problems limiting their conclusions to the conditions in which data have been obtained.

Do we extrapolate this result to people who follow a low-carbohydrate diet, who do not force themselves to consume more food than what their appetites demand, who do strength training, who follow a diet for years —instead of two weeks— and who consume real food, instead of half of their food in the form of a product that is 100% fat? Making that extrapolation is barbaric. In this article I want to talk about “scientists” who do that extrapolation.

This experiment is absolutely irrelevant for practical purposes, since it has nothing to do with the conditions in which a person would follow a diet high in fat and low in carbohydrates. Nobody defends a diet that is simultaneously high in carbohydrates and high in fat, such as the one that is used in this experiment. Moreover, in this experiment people are forced to eat in excess. But this experiment is useful a) as one evidence more of the falsity of the CICO theory and b) to demonstrate that short-term data are irrelevant for understanding long-term weight loss or gain.

The other major barrier to understanding is the focus on short-term studies. Obesity usually takes decades to fully develop. Yet we often rely on information about it from studies that are only of several weeks’ duration. If we study how rust develops, we would need to observe metal over a period of weeks to months, not hours. Obesity, similarly, is a long-term disease. Short-term studies may not be informative. Jason Fung

Further reading:


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