Why “Diets” Fail: Part I

The Science Corner

Part 1 – “The Diet Catch 22”

Trying to lose fat? You’re most likely doing it wrong…

In this series, we are going to dive a bit deeper in to the actual science behind some of the changes that take place in your body when dieting and answer some of the most important fat loss questions.

Why calorie restriction isn’t the answer to long term fat loss

Why you are eating too little to lose fat

How you are setting yourself up to fail in the long term

If you’ve ever heard the term Yo Yo Dieting, Slowed Metabolism, Metabolic Damage, Rebound Dieting…basically these are all referring to the same thing. If you diet too hard, or for too long, you 1) either find it harder to lose fat and / or 2) you get even fatter when you go off your “diet”.

This is the main reason why health professionals don’t recommend you go on any “fad” diets. Or any sort of eating plan with only a short term dramatic outlook (*cough* detox *cough*…)

Bottom line is this, if you want long term success in fat loss. You can’t just focus on restricting calories over the long term.

You can’t restrict calories too much.

And you can’t restrict calories for too long.

Which brings us to the Catch 22…

The Catch 22 lies in the fact that – if you want to lose weight – you are going to have to create some kind of deficit. But in order to create this deficit, most people will restrict how much they are eating in an effort to “cut calories”. Which is what most people would call a diet.

But if you restrict calories, you slow your metabolism down and end up burning less energy than you were before. So, after a period of time, you’re now no longer in a deficit.

So you have to restrict calories even more now to create a new deficit. But if you do, then your metabolism slows down, so you restrict more which you can’t do now, because there’s nothing left to give…aaaaand now you’re screwed…

Not only that, if you do go back to what you were eating before, you will also end up fatter than where you started, because the baseline amount of energy you are burning now is less than before.

BUT in order to lose weight you needed to create some kind of deficit…See how it gets confusing?

So what the heck is actually going on here? How do you really go about creating an environment that helps you lose fat AND not wreck your metabolism in the process?

Don’t worry. Of course I hold the answers, and we’ll eventually get there on how you can also make this work to your advantage.

But first, the boring bits you unfortunately need to understand, otherwise everything else later on won’t make sense.


To understand how your body changes and adapts to your food intake, we need to start from the beginning.

The amount of energy your body burns through each day can be simply divided up in to 2 main categories

1) Resting Energy Expenditure (REE)
2) Non Resting Energy Expenditure (nREE)

This is the fancy way of saying that your lazy lump of a body still uses energy, even when you’re not doing anything. They just decided to call it REE. The energy you burn while at rest. As you can imagine, this isn’t as much energy as when you are actually moving…which is called Non Resting Energy Expenditure or nREE. Genius right?!!

These things aren’t as basic as they appear on the surface, and I will be exploring these in more details in the future, but let’s not get ahead of ourselves. This is all you need to know for now. REE and nREE. Just nerd words for simple concepts.


Your body will change the amount of energy it burns at rest and during exercise through something known as ADAPTIVE THERMOGENESIS

“Adaptive Thermogenesis limits changes in energy stores in response to varying energy intake and / or Energy Expenditure.” (Muller et al, 2016)

Which again – freaking scientists, am I right? – is an unnecessarily complicated way of saying your body will resist what you try and do to it. Your body doesn’t like change. It’s like me as I get older. It resists any change and it is always right.

So, if you diet too hard, or for too long it will try and preserve itself. I know, I know, this is nothing new. People have been saying this for years. But, you know what, no one’s listening properly and every few years some new “guru” comes out with a fancy new term that creates a revolution in the diet industry (metabolic damage I’m looking at you) and people lose their minds like they’re the new messiah. So PAY ATTENTION!!

Here’s the simple math



You take in less energy, your body will change to burn less energy

You eat too much, your body will actually burn more

Adaptive Thermogenesis does this by:

Negative Energy Balance – AT will affect mainly your Resting Energy Expenditure, your body will burn less even when you are doing less

Positive Energy Balance – AT will affect mainly your Non Resting Energy Expenditure, your body will actually burn MORE when you do exercise

Negative Energy State:

When you “diet” by restricting calories, you will mainly affect your Resting Energy Expenditure. This is what people refer to as a slowing metabolism. Basically, the worst thing you can do to try and lose weight is to just cut calories and make no changes anywhere else.

Positive Energy State:

When you overconsume calories – at least in the short term – your body will dissipate a lot of this excess energy when you are performing exercise. Simply, the energy you burn during a workout will be MORE when you over consume your calories compared to a workout when you under consume.

So, remember our Catch 22 again? You need to eat less to create an energy deficit in order to lose fat. But if you do, your body will burn less energy, which means it will be harder to lose fat. But you need to create an energy deficit, but if you do….

And it all comes down to the concept of Adaptive Thermogenesis.

Sounds like you’re wasting your time doesn’t it?? Well, if your only approach to losing fat is simply cutting calories, then yes, you are setting yourself up to fail in the long term, but potentially causing yourself some long term effects that will not only make it harder for you to lose fat in the future, but will also most likely make you fatter in the long run.

Remember, there are two sides to the energy equation. There is energy in and there is energy out. What people sometimes forget is this is an INTERDEPENDENT relationship.

Meaning, your energy out is actually dependent upon your energy in!

And most people still think of this equation in simple black and white terms “I need to burn more energy than I consume, therefore I will cut calories”. Which may get you results in the short term, don’t get me wrong. But it also comes at a cost down the road. What they’re not realising is just by cutting calories, they are affecting the “energy out” side of the equation and are actually burning less!

The other problem is, if you over eat for too long or overeat the wrong types of foods, you can also mess up some of these processes. Damaging your metabolism is when your body stops responding to these changes in energy intake in the appropriate fashion.

How someone who is overweight responds to changes in energy balance is actually different than someone who is leaner. An overweight person WON’T have the same energy dissipation response to overfeeding as a leaner individual as they have essentially broken their metabolic response system. But again, I digress…

If this has raised more questions than it has answered so far, then good!!! It should have. Because there are answers to all of these problems and more.

What is actually happening in Adaptive Thermogenesis? What does it actually mean when someone says your metabolism is slow? And more importantly, what the heck can you actually do about it so you don’t get stuck in the same cycle of “dieting” over and over again with limited success.

In the next instalment we will be exploring Adaptive Thermogenesis in more detail and look at what is really happening inside your body. We’ll further break down your REE and nREE and see how they adapt and behave to different energy intakes and explore how you can even INCREASE the amount of energy you burn when you eat more.

For now though, let’s summarise what we looked at today.


Your body burns energy each day both while resting and during activity. These are called Resting Energy Expenditure (REE) and Non Resting Energy Expenditure (nREE).

Adaptive Thermogenesis is your bodies response to energy intake to try and preserve its energy stores.

Negative Energy Balance equals less energy you will burn (mainly affecting resting metabolism or REE)

Energy Surplus equals more energy burned (usually during exercise or your nREE)


Müller MJ, Enderle J, Bosy-Westphal A. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Curr Obes Rep. 2016;5(4):413-423. doi:10.1007/s13679-016-0237-4