Why “Diets” Fail: Part III

The Science Corner

Part 3: Low Metabolism vs High Metabolism, How to Cheat The System

The last couple of instalments have focused on the outcome of Adaptive Thermogenesis. The end result of what happens when you eat too little vs what happens when you overconsume.

We have looked at the different parts that make up our “energy out” side of the equation and we have also looked at how Adaptive Thermogenesis can influence different aspects of these separately.

Each instalment we have been peeling off the layers gradually, slowly uncovering the details that make up your metabolism. This next part will dig even deeper still. Deep inside your body to understand exactly what is happening to cause this change.

Once you have an understanding of the different factors inside your body that influence this Adaptive Thermogenesis, you can then use them to help “cheat” the system. You too can also learn to maximise the good and offset the bad.

In other words, you can learn to get lean, stay lean, and eat big doing it.

In this instalment:

  • You will learn exactly what it means when someone says they have a high metabolism.
  • You will understand that people who seemingly eat the house down and stay lean don’t defy the laws of thermodynamics.
  • And you will understand why what’s happening inside your body when you somehow lick a cookie and get fat while your PT eats a stack of pancakes and still retains a six pack.

Most importantly, you will learn the details on how you can start training your metabolism to do the same.

KEY IMPORTANT SCIENCY THING NUMBER 1: Adaptive Thermogenesis is Fluid And Shifting

The good news (and bad), is that adaptive thermogenesis is always changing. It’s ALWAYS searching, trying to reach a new “balance point”.

Even though your metabolism is governed partly by your genetics, you are not a slave to it. There is a large component of it that you CAN influence. For better or worse. Most people do it for worse…

It might take some people a bit longer to recover from a “poor metabolism”, but EVERYONE can change it for the better.

What is also means is this…

Your so-called “ageing metabolism”, has in fact got nothing to do with age, but the many years you’ve spent with bad eating and exercise habits.

So, what determines this metabolic balance point? And what exactly is your body adapting or responding to?

What Happens When You Lose Weight?

“Adaptive Thermogenesis relates to two different set points with a settling between them.

  1. During early weight loss, the first set is related to depleted glycogen stores associated with the fall in insulin secretion where AT adds to meet brain’s energy needs.
  2. During maintenance of reduced weight, the second set is related to low leptin levels keeping energy expenditure low to prevent triglyceride stores getting too low which is a risk for some basic biological functions (e.g., reproduction).” (Muller, et al, 2016)

In the early days of losing weight, the adaptive thermogenesis response is all to do with blood glucose levels, the glucose levels stored inside your muscles and insulin levels. It’s all about preserving energy for the brain. If the brains needs are met, metabolism is sweet. If these start getting a bit low, your body will start making some changes.

We discuss controlling the outcome of the first “set” i.e. response to glucose and insulin a section a bit further below.

Later on though, it’s all about trying to preserve some fat stores.

As time goes on and you lose some body fat, your body starts pushing back against you. As far as your body is concerned, it doesn’t know you are trying to get a sick striated ab line for the beach this summer, it just thinks you are slowly starving yourself to death. So, in response to this, it slows your metabolism down to conserve energy.

One of the biggest mistakes you can make is thinking you can have a 6 pack all year round!!

Everyone thinks that bodybuilders and fitness models are in competition shape all year round, and this simply isn’t the case!! In fact, your fitspo’s feed is taken up of 1000 pics they took 2 weeks out from their comp, they’ve just been milking the same photo shoot for the past 10 months!!


This is why people who have competed in bodybuilding wreck themselves metabolically during the process. Guys end up with the testosterone levels of a nat. And women tend to disrupt their cycles and rebound with their weight…hard. This brought about the buzz term “metabolic damage” that was all the rage in the industry a few years back.

Everybody blamed their prep coach, when really it was just a consequence of competing in a sport demands super low levels of body fat.

But, through all of that? ALL of them can make a recovery.

Same goes the other way when you carry a bit too much body fat for too long. The body’s response and response time is a bit off, and it might take some finessing to get there. But it DOES get there.

Easy come easy go. Don’t diet too hard. Don’t diet too long. Any extreme one way or the other is bad.

You can push it too far sometimes and it might seem a bit broken. But it ALWAYS CAN RECOVER.

Take home message:

  1. Your goal shouldn’t be to get too lean and stay there.
  2. Be patient at the start if you have been overweight for a period

It is always a shifting and changing process and your metabolism will always adapt. You are never a slave to it. Use that to your advantage.

What Happens When You Have a High Metabolism?

What’s the deal with your PT or insta hero that can seemingly eat pancakes and burgers every week and NOT GET FAT?

We all knew that one person growing up that seemingly ate their household out of food and gained ZERO weight. What is really going on with someone who has a “high metabolism” where they create this metabolic trickery where the laws of energy in energy out don’t seem to apply.

“Metabolically, AT has been explained by the ratio of glycolytic to oxidative enzymes together with an altered efficiency of free fatty acid oxidation in skeletal muscle, “futile” cycles consuming ATP without a net change in products (e.g. hydrolysis of triglycerides and subsequent re-esterification in adipocytes), changes in the ATP-costs per muscle contraction, mitochondrial uncoupling in brown adipose tissue, energy-consuming pathways like lipogenesis, NEAT and/or partitioning of energy to fat mass or FFM [3]. These mechanisms are considered to be under genetic and hormonal control, i.e. by insulin, leptin, thyroid hormones and sympathetic nervous system (SNS) activity.”(Muller, et al, 2016)

English Translation:

In people with a high metabolism, their bodies respond differently to an increase in calorie intake. Their body will essentially burn through energy with “futile” energy consuming reactions.

This is the metabolic version of spinning its wheels.

Or digging a hole then filling it back up again, then digging a hole then filling it back up. It wastes energy, and doesn’t change anything.

Just like the above though, don’t think for a second that those with a high metabolism get away with this forever. It does catch up with them if they do it for too long.

This is why you’ll find those that are lean and post a lot of pics about the “crap” they eat, actually eat pretty controlled the rest of the time.

It’s all about finding a sweet spot. Getting lean enough without getting too lean. Being able to plan and overconsume without “over” consuming.


Now the moment you’ve all been waiting for, what is it that regulates this mystical Adaptive Thermogenesis?

How do you turn YOUR metabolism from a Datsun 1200y (if you get that reference, you are too old, welcome to the club) in to a high performance sports car?

“Regulation of AT has been related to changes in the composition of FFM (i.e. a change in the proportion of high metabolic rate organs to muscle mass as well as tissue hydration), reduced endocrine signals from triiodothyronine (T3), insulin and SNS activity and/or a reduced feedback from adipocytes brought about by a fall in leptin secretion.”(Muller, et al, 2016)

What this again means in English…Your AT is regulated mainly by

  • Fat Free Mass – muscle and high metabolic rate organs as well as tissue hydration
  • Thyroid
  • Insulin
  • Sympathetic Nervous System (i.e. adrenalin, cortisol)
  • Fat Hormones i.e. Leptin is a fat released hormone that tells the brain if you are “full” or “hungry” and also controls metabolism

In other words, you need more muscle. AND you need optimisation of your body’s hormone system.

The most important point here:

ALL of these processes are controlled by more than just your “energy” intake. Yes, genetics has a lot to do with it, but hormones make up an intricate part of a huge overall network woven together and dependant upon one another in complex networks and feedback loops.

In other words, these hormones are governed by more than just your calories, so there’s more to the picture of your overall metabolism than just your calorie intake.

For you though. What you need to know right now:

  • You need to lift weights
  • You need to carefully construct your diet to not only create an effective negative energy balance
  • You need to do so while optimising the right hormonal balance.

On top of the relative factors we have discussed so far on energy intake, you now need to add in carefully constructing your macronutrient intake.

KEY IMPORTANT SCIENCY THING NUMBER 3: There’s More To It Than Just The Calories

“We assume that in early starvation, lower thresholds of (i) liver glycogen or (ii) negative fluid balance associated with glycogen depletion trigger AT. It is tempting to speculate that this early response is related to energy needs of the brain (i.e. brains metabolism requires 80 to 100 g glucose per day). By contrast, AT does not occur after glycogen depletion in response to an isocaloric ketogenic diet and moderate weight loss” (Muller, et al, 2016)

As hinted at previously, this is a crucial element, as it raises the point that creating this optimal environment and negative energy balance is more than just “calories”.

What this is saying is that you can actually offset some of the negative aspects of AT when you keep the calories the same on a lower carb diet

This might also contribute to partially explain why lower carb diets work better in the short term compared with higher carb diets when calories and fluid changes are equated for.

Basically, Macro’s Matter. Not just the “calories”.

In fact, when reviewing these and other aspects of true energy intake, Macro’s matter MORE than calories. Focus on hitting your macro targets as a priority and place this in the context of your overall calorie intake.

When it comes to maximising your metabolism:

  • You want a diet that maximises food intake while creating an optimal energy deficit (i.e. optimising Thermic Effect of Feeding, etc)
  • You want a diet that controls blood sugar and glycogen levels without adversely affecting Adaptive Thermogenesis
  • You want a diet that promotes lean mass and optimisation of fat loss hormones without disrupting your hormonal balance
  • You can do all of this by correctly calculating out your macronutrient values for your given calorie intake.


Adaptive Thermogenesis is not a life sentence, it’s a constant fluid and shifting progress. This is one of the reasons why no diet works forever and constantly needs to be changed depending on how your body is adapting.

It is under the influence of muscle, food intake and hormones. It’s about energy balance, but this energy balance is more than just calories, as the things that influence AT are also the composition of those calories and the effect these also have on muscle, hormones, etc.

Let’s Bring it Back Real Simple, The Take home messages so far on AT

  1. Don’t Starve Yourself to weight loss, mild calorie restrictions
  2. Planned Diet Breaks and refeeds can help to normalise your AT response and increase the energy you burn during exercise
  3. Optimise Your Hormones
  4. Your Macronutrient Amounts / Ratio’s Matter – There are more ways to create a deficit than just eating less as the “energy out” part of the equation is a lot more complex than people originally think.

You can cheat the system, or you can break the system. A broken system means you have slowed everything down or metabolically changed how your body responds to different stimulus i.e. type II diabetes or insulin resistance, you don’t get the same responses as someone with a higher tolerance to higher calorie intake and insulin sensitivity for example.


You’ve now finally created yourself a successful energy deficit!!

Only one little problem remains…


Final part of the series we discover Energy Partitioning and how you can wire your metabolism to tap in to body fat and preserve your hard earned lean mass.


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