Why hypocaloric diets won’t help you lose weight? (1/2)

(Versión en español: hacer click aquí)

There is no excuse. People who are obese are so because of their inability to follow a diet plan and exercise. If they did that, they would lose their excess weight.

We calculate the energy expenditure of our body, we discount a few hundred calories, we adjust our intake to that number and we increase our physical activity. It can’t fail, right? But it doesn’t work. And the «experts» have no doubts that the problem is that people don’t follow their instructions. If only they had a little willpower! If only they were virtuous, as thin people!

In a time of crisis, you waste less and you get more of what you have

And so does our elephant (see,see,see), whether you aknowledge it or not. If it doesn’t get enough food, it will spend less energy and it’ll be more efficient with its energy expenditure. Our elephant doesn’t want to starve and it defends itself from the perceived situation of lack of food. And you won’t deceive it, because it has food or it hasn’t, no matter the tricks you use to give it less food than it asks or needs. Weight loss is not about appetite control, or deceiving hunger, but about understanding how your elephant behaves.

The challenge with your elephant is one you can’t win

Is that so?

Yes. First of all, because the scientific evidence is overwhelming: eat less and exercise more doesn’t lead to a significant weight loss in the long term (see). And the reason doesn’t seem to be that people give up the diet, because it doesn’t work either when caloric restriction is sustained over time (see). Moreover, you don’t need scientists to know that, because it is what we see with our own eyes: people are unable to lose weight and stay slim just by eating less.

Have a look at the following scientific experiment: two years in duration, in which weight is lost during the first six months.On average participants lost 14% of their weight, about 9 kg. Then the weight is kept stable for eighteen months. The experiment ends at the 24th month. The graphs below show the weight lost by each participant in Kg (graph on top) and  the same data as a percentage of the initial weight (graph on the bottom).


The most interesting result from this study is that after those two years, after one and a half years keeping their weight stable, subjects’ metabolism was still altered. Their body burned virtually only carbohydrates and no fat. The body was in a «fat gain mode». Six months after completing the experiment (month #30) they had already recovered the lost weight, something you can see on the right side of the previous graph. And their body was still «impaired»: it was still burning less fat than a control person who had not lost weight and gained it back. In the graph below this lines the white box shows the daily amount of burned fat. Data is shown for a week after the end of the experiment (month #24) and six months after the end of the experiment (month #30), compared with a control group:


At the end of the the experiment, month #24, the total energy expenditure of the participants was 1770 kcal, compared with 1950 kcal before starting the experiment. In other words, after one and a half years keeping their weight stable, their metabolism was reduced by almost 200 kcal/day and burning virtually no fat. Six months after the end of the experiment, month #30, the participants’ body mass was 68.5 kg on average, compared to 68.3 Kg in month #0. And their energy expenditure was 1840 kcal/day, still lower than the baseline value of 1950 kcal/day. They had already gained the weight back and their energy expenditure was still reduced.

My conclusions

In short, when forced to suffer a caloric restriction and weight loss, our elephant reduces its energy consumption and gives priority to body fat gain (So cute! it only wants to store fat so it has no energy problems in the future!). These physiological changes remain in the long-term and smash the possibility of keeping the weight loss in the long term.

If we also take into account that hypocaloric diets make you hungry, it is very likely that given the absence of benefit and being that hungry, the person choses to eat a normal amount of food. That will only speed up the inevitable, which is to regain the lost weight. But even if you don’t start eating a normal amount of food, you will not get good results.

Some people say that even if hypocaloric diets don’t work for weight loss, at least for a while (until you return to the baseline weight) your health benefits from a smaller body mass. I don’t think it is clearly so. Losing weight following a low calorie diet is a bad idea that can damage our body in the medium and long term. Dieting may have benefits, but it also has a risk. You can’t advice people to lose weight with caloric restriction without warning them that 1) the method doesn’t work for long term weight loss and 2) they can damage their metabolism. Moreover, scientific evidence (see) suggests that «dieting», by itself, increases the risk of gaining weight in the future. «Eating less» is not a path without consequences.

Read the second part of this article: 


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  1. Pingback: On calories, morons and stupidities blessed by the majorities | No vuelvo a engordar

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