Why Caloric Reduction Doesn’t Work – Calories Part IV

By Jason Fung, MD

This is a continuation from Calories part III. You can start here for part I. We were discussing assumptions in the Caloric Reduction as Primary model…

Assumption#4 Fat stores are essentially unregulated

All systems in the body are regulated. If you consider any system in the body, it is a regulated system. For instance, growth in height – regulated by growth hormone. Blood sugars – regulated by insulin and glucagon, among others. Sex – regulated by testosterone and estrogen. Thyroid – regulated by thyroid stimulating hormone and free thyroxine. It goes on and on. Any bodily function you can imagine is under some regulatory system – usually hormonal (endocrineparacrine, autocrine etc.).

We are asked to believe, however, that growth of fat cells is essentially unregulated. The simple act of eating, without any interference from other hormones will result in fat deposit growth in our body. The extra calories are dumped into fat the same way one would dump a few leftover potatoes into a sack.

In fact – we already know that this is essentially untrue. We are discovering new hormonal pathways in the regulation of fat growth all the time. Leptin is one such pathway. Adiponectin is another potential pathway. Hormone sensitive lipase may be important. Cortisol may play a role, as well as lipoprotein lipase (LPL) and adipose triglyceride lipase (ATGL). And, of course, our dear old friend, insulin. We will be talking about insulin in much, much more detail in future posts. Much more.

So, let’s recap…Here are the 4 key assumptions in the Caloric Reduction as Primary (CRaP) theory which are all false:

1. Calories in and Calories out are independent.
2. Conscious control of Calories in.
3. Conscious control of Calories out.
4. Fat stores are essentially unregulated.

It is important to note that in this model, this is a causal relationship. That is, eating too much causes obesity. Therefore, from a scientific standpoint, we can easily test this hypothesis.

We can do this by manipulating the variable of eating. According to the CRaP hypothesis, eating too much causes obesity. Therefore eating less will reduce obesity. We would predict that by reducing the amount we eat then obesity should be reduced. Basal Energy Expenditure (BEE) is assumed to be not affected by changes in caloric intake.

That is an easy study to do. We take some people, give them very little to eat, and watch them lose weight and live happily ever after. Bam. Case closed. Call the Nobel committee. Luckily for us, those studies have already been done.

The first such study was done almost 100 years ago. Entitled “A Biometric Study of Basal Metabolism in Man”, it was done in 1917 at the Carnegie Institution of Washington’s Nutrition Laboratory on 12 healthy young men. They were put onto ‘semi-starvation’ diets consisting of 1400-2100 calories per day and then observed with measurements of energy expenditure taken.

That doesn’t really seem like such a drastic diet, considering some of the low calorie diets that are out there now. Many of the current studies, such as the LOOK AHEAD study recently published use very similar levels of caloric intake.

What happens to the body if you suddenly restrict caloric intake? According to the CRaP hypothesis, the Total Energy Expenditure (TEE) should remain the same. Reduce calories and keep TEE constant will result in burning fat for energy and patients should lose weight. Sounds great.

However, in reality, TEE dropped substantially – a whopping 30%. The men complained constantly of being unable to stay warm, even with an “abundance of clothes”. Heart rate and blood pressure dropped. Men showed a marked inability to concentrate and marked weakness during physical activity. In other words, their metabolism was shutting down.

Let’s think about what is happening here. Let’s assume the these people normally eat 3000 calories per day. Since they are neither gaining nor losing fat, they are burning 3000 calories per day. Now we restrict calories to 2000 calories per day. With roughly a 1/3 reduction in calories the body responds by reducing caloric expenditures (shutting down).

Calories are needed to heat the body. So, the body turns down the body heat. Result – the patients feel cold, no matter how much they try to put on clothes.
Calories are needed to pump the heart. So, the body slows that down. Result – heart rate decreases.

Calories are needed to maintain blood pressure. So, the body turns that down. Result – blood pressure decreases.

Calories are needed to think (brain is very metabolically active). So, the body turns that down. Result – inability to concentrate.

Calories are needed to move. So, the body turns that down. Result – weakness during physical activity.

In other words – the body more or less imposes an ‘across the board’ reduction in caloric expenditure. Just like hospital budget cuts where everybody gets an ‘across the board’ budget reduction. They wreak havoc in the hospital and they wreak havoc on the body.

Why does the body do this? Well, because the body is smart and doesn’t want to die. Consider a person normally eating 3000 calories a day. Now, he eats 2000 calories a day. If he were to continue to expend 3000 calories daily, he would soon burn all his fat store, then his protein stores and then he would die. Nice. Why would he want to do that? The smart thing to do is to immediately reduce caloric expenditure to 2000 cal/day to restore balance. Why do we assume Mother Nature is so damned stupid? We assumed that reducing calories by 1/3 would be met by the body with no change in basal energy expenditure? Yes, we did.

The rational person would adjust to the new 2000 calorie a day diet by reducing energy expenditure to not just 2000 calories but a little less (just in case), say 1900 calories. This is exactly what the body does. Because it is the SMART thing to do.

What happened to weight? The men did initially lose weight, but what happened next is probably familiar to all those who have tried to diet. After the experiment ended, they regained all of that weight and even a little bit more. The TEE (or Calories Out) dropped so substantially that returning to a normal diet meant that the men started to regain the weight. When they lost the weight, they lost muscle and fat. When they regained the weight, it was all fat.

Let’s think about this in terms of the standard Caloric Restriction as Primary (CRaP) diets. Let’s say we impose a daily calorie restriction of 500 calories a day, by some advice such as ‘portion control’ or some such nonsense. I would expect TEE to be reduced by 500 calories a day. I would expect that person to become cold, tired, hungry and (probably) irritable. Weight would initially be reduced, but the would be regained as the body made the adjustment. As they went off the diet, all weight would be regained with a little extra thrown in for good measure. Sound familiar to anybody? Sounds familiar to everybody.

Continue to Calories part V 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

For many health reasons, losing weight is important. It can improve your blood sugars, blood pressure and metabolic health, lowering your risk of heart disease, stroke and cancer. But it’s not easy. That’s where we can help.

Jason Fung, MD

By Jason Fung, MD

Jason Fung, M.D., is a Toronto-based nephrologist (kidney specialist) and a world leading expert in intermittent fasting and low-carb diets.

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