How Do We Gain Weight? – Calories Part I

By Jason Fung, MD

This is the single most important question in obesity. It is impossible to adequately treat any disease without having some understanding of the cause (the aetiology). For instance, if you understand the cause of infections to be bacteria, then you can target bacteria in its treatment. This leads to hand-washing as opposed to, say, leeching. So, how do we gain weight – or more scientifically- what is the aetiology of obesity? That is the question we should be asking.

However, very little time is spent considering this all-important question because we feel that we already know the answer. It is a matter of calories in versus calories out, we say. Eating too much and exercising too little causes obesity, we say. We hold these truths to be so self-evident that we do not even for a minute question their veracity (whether it is true).

We also consider that the reason we eat too much or move too little is because of personal choice. That is, we choose what we put in our mouths and therefore are responsible for what we eat. We could have eaten broccoli instead of that bag of chips. We could have run for an hour instead of watch TV.

In other words, obesity is a personal failing – that the cause of obesity lies in the individual. Eating too much (gluttony) or moving too little (sloth) are individual failings – in fact, 2 of the 7 deadly sins. If we ask the ‘experts’, they agree that the key to weight loss is eating less and moving more.

Holy consensus, Batman. With so many ‘experts’ from Michelle Obama to the USDA to virtually all of the medical professionals (including doctors and dieticians) agreeing that ‘Eat Less, Move More’ is the way to go, you might think that it is 100% unquestionably true. But here’s a queer thought… if we all agree that we know the cure for obesity, and we’ve spent billions on educations and programs – why are we getting fatter? In other words, why does this ‘cure’ suck so bad?
Let’s back up. If the cause of obesity is eating too much and exercising too little, we can think about obesity in this way:

I call this the Caloric Reduction as Primary (CRaP) hypothesis. This means that the primary (but not the only) factor in obesity is calories and reducing calories is the mainstay of treatment. Furthermore, the reason behind eating too much is not hormonal, not hunger, but personal choice. It can also be called the “Calories in, Calories out” model (CICO), and is often depicted as a scale. Calories not used in exercise will be deposited as fat.

The assumption is that if fat mass is stable, then the calories taken in must be balanced by the calories utilized by the body. How the body uses these calories of energy is presumed to be mostly by exercise. However, this is not true since the body can choose how to expend the energy ingested. Let’s look at an example.
If we consume 2000 calories of energy, those 2000 calories can have very different metabolic fates. Are those calories burned as heat (Resting Energy Expenditure), used in production of new protein/ bone/ lean muscle, used in exercise/ physical exertion, or deposited as fat? We don’t mind if energy is burned as heat, but we DO mind if it is deposited as fat.

Furthermore, the “Calories Out” is not so stable as we seem to think. It can go up to 3000 calories/day in some people and down to 1200 calories/day in others. It can also change depending on what we eat. So we can see that one simple “Calories Out” pile is not really so simple.

According to this view of obesity we can think of fat storage this way:

Fat Storage = Calories in – Calories out
When you think about it in this way, it seems that Fat Storage is determined by Calories. If we assume that “Calories out” is fixed and never changes , then it means that “We are getting fat because we are eating too much”. Now the assumption that ‘Calories Out’ is fixed is false, but let’s simplify for the moment.
But we can re-arrange the equation in this way:

Calories in = Fat Storage + Calories out
If we assume again that “Calories Out” is fixed and never changes (false), then the implication here is that “Calories in” depends on Fat Storage. The means that the amount we eat is determined by whether or not we are in “Fat Storage” mode. This now sets us up to ask the correct question – What is causing us to be in Fat Storage mode? In other words “We are eating too much because we are getting fat”. That begs the proper question “Why are we getting fat?” or “What is the aetiology of obesity?” – the central question of this blog and the root cause of obesity, diabetes, heart disease, cancer and most of the so called diseases of civilization.

Both equations are equally true and do not violate the “First Law of Thermodynamics”, but the implication is entirely different. Which of these interpretations is true?

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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