Why Diets Don’t Work in the Long Term – Calories Part VII
By Jason Fung, MD
Click here for Calories Part I, Part II, Part III, Part IV, Part V, and Part VI.
We have explored the body’s adaptation to reducing calories and weight and seen how the body acts more like a thermostat than a scale. The body acts as though it has a Body Set Weight (BSW) and strives vigorously to defend that weight against increase or decrease alike.
But how long do these adaptations last? If we maintain a certain body weight, will our body eventually recognize this as a new BSW? Certainly at first glance, this seems like a reasonable assumption. But is it true?
Reduce Energy Expenditure
Let’s look at some recent studies to answer this important question. Long-term persistence of adaptive thermogenesis in subjects who have maintained a reduced body weight by Dr. Rosenbaum et al.
In this study, 21 subjects were recruited and fed a liquid diet consisting of 45% carbohydrates over one year and the Total Energy Expenditure (TEE) were measured. As expected, during the initial weight loss phase (10% of body weight) TEE was reduced. As weight went down, the body tries to regain the weight by reducing TEE. In essence, the body is defending the BSW and trying to return to the original weight. But how long does this last?
What is interesting is that TEE is reduced over the course of the full year. Even after one year at the new, lower body weight, the TEE was still reduced by an average of almost 500 calories/day. (see figure on right)
In other words, this reduction in TEE starts almost immediately after caloric reduction and persists for a long time – at least 1 year and going strong. It does not appear that this BSW has been changed at all. There is no sign that BSW has changed.
The body is still trying to get back to the original BSW. Remember that this weight loss is achieved with no change in the composition of the diet – only the amount (a portion control strategy).
Let’s put this into dietary terms. We start by eating 2,000 cal/day and burning 2,000 cal/day. We decide to lose some weight and reduce our calories to 1,500 cal/day. Our body almost immediately reduces TEE to 1,500 cal/day.
We lose some weight but then the weight loss stops even though we are still eating less than before. Because TEE has been reduced, we feel cold, tired, hungry and a bit miserable but we decide to stick it out thinking that things must improve. However, even after 1 year, things are exactly the same. We feel lousy and the weight is not coming off despite our best efforts to eat only 1,500 cal/day.
Finally, we think that we should go back to a normal diet 2,000 cal/day. The weight comes rushing back because now we are eating 2,000 calories/day and expending only 1,500. Sound familiar? Thought so… That’s because everything I’m describing here has been well described over the last 100 years!
This actually starts to make a bit of sense. Suppose we are the manager of a power plant. Every day, we receive 2,000 tonnes of coal and we burn 2,000 tonnes of coal. We also maintain a supply of coal just in case we don’t have enough (storage shed). Now, all of a sudden, we start getting only 1,500 tonnes of coal.
What do you imagine that we should do? If we keep on burning 2,000 tonnes of coal, we would quickly burn through our stores of coal and then our power plant would be shut down. Massive blackout over the entire city. Anarchy and looting commence.
Our boss would tell us how utterly stupid we are and say something like “Your ass is FIRED!” The problem, of course, is that he is entirely correct in his assessment.
Because we, as the manager of this power plant, are not that stupid would not do that. As soon as we figured out that we were only getting 1,500 tonnes of coal, we would reduce our power output to 1,500 of coal. In fact, we might use only 1,400 tonnes just in case. A few lights go out, but there is no blackout. Anarchy and looting avoided. Boss says “Great job. You’re not as stupid as you look. Raises all around”
Now, let’s think about our body. We eat 2,000 calories/day and use 2,000 calories/day. We start a diet so now we are eating only 1,500 calories/day. What happens? Well, the body is not that stupid. It does not want to die. Why do we assume the Mother Nature is a complete moron? The very first thing we do is reduce our TEE to 1,500 calories/day and maintain that for as long as it takes.
We know for a fact that this is what happens. It has been proven over and over again. We just keep not believing it and hoping that our caloric reduction strategy somehow, this time, will work. It won’t. Face it. We only believe it because the nutritional authorities keep tell us it works. It doesn’t.
Mother Nature is not stupid. That’s why conventional calorie reduced diets don’t work in the long term.
Continue to Calories part VIII here
Begin here with Calories I
Click here to watch the entire lecture: The Aetiology of Obesity 1/6 – A New Hope
By The Fasting Method
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