Fat Adaptation and Intermittent Fasting

Fat Adaptation and Intermittent Fasting

13 September 2020

by Dr Paul B Chell and Dr Monique Hope-Ross

Fat adaptation can be achieved by a combination of a low carb diet and intermittent fasting. Fat adaptation allows you to burn fat and lose weight. Using fat to fuel is a natural process, but may need to be trained-the process of fat adaptation.

On a personal level you or your loved ones are told by the doctor, “you are overweight, or you have type 2 diabetes, and take these tablets”. And in the modern world this can happen to any of us. The pathway to this is obesity, then visceral fat, metabolic syndrome, pre-diabetes, then diabetes, then all the consequences; and they’re far from amusing. Often, because this is a common diagnosis, patients and doctors alike, do not sit back and think, what the heck is happening here?

Well, it’s very simple. The 10 stops on the fast track bus to the grim reaper is one we all recognize, and it goes like this;

  1. Stress
  2. Sedentary lifestyle, little exercise
  3. Diet rich in sugar and carbs
  4. A bit of a tummy
  5. Overweight, then obese
  6. Visceral fat around our organs (also called belly fat)
  7. Metabolically active visceral fat grows
  8. We develop metabolic syndrome
  9. We become leptin resistant, leading to increased appetite
  10. We become insulin resistant, leading to diabetes type 2

How to Reverse Obesity

Reversing obesity means your body needs to undergo fat burning. Rather like a hybrid car, the body has two fuel systems-one which uses carbohydrates and one which uses fats.

Fat adaptation is the process by which we change the body from carbohydrate burning to fat burning. More accurately, we re-learn our fat burning, weakened by years of carbohydrate addiction. Our fat stores, which are vast, even in lean individuals will be used for our body’s energy rather than our daily dietary carbohydrates.

Top Tip

Reversing obesity means your body needs to undergo fat burning

The hormone, insulin is the key to this process. If insulin is circulating, you are not burning fat. It is that simple. You need to avoid a large insulin spike, which is usually released with a snack or meal containing sugar. From the chart we can see that fat has a very much smaller insulin response compared with carbohydrates, with protein between the two. Ideally, we want a small insulin response; that is the area under the line on the graph to be small and short, so we can return to fat burning .

Hunger is driven by eating carbs; increasing with the frequency and the refinement of the carbs. So, our feeling of hunger is always, and I repeat always, caused by the hormonal effect of the last snack or meal.

Top Tip

Our feeling of hunger is always caused by the hormonal effect of the last snack or meal.

If this describes you then you may have;

Fat fuel inhibition

This is our body’s inability to switch from using carbs as a fuel to using fat for fuel. We have effectively made ourselves addicted to the short-term rush of refined and super-refined carbohydrates. A cycle repeated over and over during the day and sometimes even at night. Check if you recognize any of these symptoms of Fat Fuel Inhibition:

Symptoms of Fat Fuel Inhibition

  • Food does not fill you up, or give you a feeling of satiety
  • After meals, you often feel tired
  • You get low energy periods during your day, particularly after lunch
  • You desire a siesta in the afternoon
  • You lose weight for a period of time, only to put it back on
  • ou have mood swings during the day, particularly irritability
  • ou are often hungry, and snacking brings relief
  • When hungry, you get shakes, and or get sweaty
  • When hungry, you get headaches or migraines
  • You find it hard to sleep on an empty stomach
  • You wake during the night feeling hungry
  • A snack makes you feel normal again
  • You get brain fog if you don’t snack
  • You tend to eat carbs for snacks; pastries, cake, muffins, cookies, candy bars
  • You drink soda drinks to satisfy your hunger symptoms
  • You are not able to incorporate intermittent fasting into your dietary regime

If you suffer just one of these, you may well have fat fuel inhibition. The great news is that with a little help we can turn this around and put you back in control.

Our bodies are very adaptive; that is, they get used to the change. If you don’t believe me think about walking or jogging. If you do it correctly your body soon adapts, and you find it easier. This is adaptation. As we humans increased the carbs in our diet, we went from being fat adapted to carb adapted. Even worse, our enzymes for fat burning became fewer and weaker. So, when we try to burn fat, we find we are fat fuel inhibited. When we first try, it’s what makes us feel terrible. We need to build up these enzymes and pathways, so we are just as comfortable on either fuel. Now that Monique and I are fat adapted, it is by far our favourite state. We feel well and generally so much healthier and clearer of mind. We have no feeling of needing food.

Fat Adaption

Fat adaption is the first secret to ridding ourselves of excess fat. For the past 100 years we have fed on too much refined carbohydrate, at too high a frequency; think snacks. Our fat burning is switched off by refined carbohydrates, and snacking. And the more months and years we do this, the more reliant we become on glucose as our fuel.

Corporatism is telling you to eat more food, more refined and more often. Just empower yourself, by doing the opposite. It is difficult for a week or two, but when you get there, it will be worth it. You will not even imagine how this will change your physical and mental wellbeing. And as many of my patients tell me, their lives are now filled with joy and spirituality. Joy that had long since been subsumed under the blanket of refined carbohydrate human misery. Fat adaptation puts you back in control of your weight and your wellbeing, both physical and mental.

Fat Adaption at the Cellular Level

Mitochondria are our cellular power stations. These tiny organelles lying in the body of our cells, or cytoplasm, produce our ATP energy tokens from oxidative metabolism. They do so from fats or carbs. When we fat adapt over time on a low carbohydrate or intermittent fasting regimen, our cells undergo some changes. And fastest of all when we do both.

Like all organelles, our mitochondria naturally become old and are continually replaced. This process in cells is known as autophagy, or specifically for mitochondria, mitophagy. This replacement cycle depends on your age, your genes, your fitness and how much exercise you take. Mitochondria need to be fat adapted to burn fat. For some people, their mitochondria will become fat adapted in 2-4 weeks, whilst in others it may take several months for all tissues to get fully fat adapted. Fat adaptation increases the size, turnover, efficiency and number of mitochondria. When you are fully fat adapted, your mitochondria in all cells will be happy burning fats as well as carbs. Your hormones will be better balanced, and you will be feeling healthy.

Top Tip

When you are fully fat adapted, your mitochondria in all cells will be happy burning fats as well as carbs. Your hormones will be better balanced, and you will be feeling healthy.

Fat adaption: the metabolic switch

Fat adaptation is a state in your body when your mitochondria in every cell utilises fats for fuel as their primary source of energy. We talk about flipping the metabolic switch from carbohydrate metabolism to fat metabolism. This metabolic switch has powerful health benefits. When you can do this, disease resistance is boosted, inflammation is reduced and both your mental and physical performance increase. Your insulin is raised less and less frequently. Your body can break down fat for fuel. Your brain will also be adapted to life on 70% ketone bodies.

Your body and brain are now fully adapted to your new low carb diet, intermittent fasting and cessation of snacking. Ketone measurements can at best be confusing. They may be useful when you start out to tell you when you are in a ketotic state. And by definition you will have to remain ketotic for fat adaptation to occur. There is no magical test to tell you when you have started to fat adapt or when it is completed.

Signs of Fat adaption

  • Your brain will be clear, cognition and memory improved
  • Hunger will have disappeared or be very low
  • After a meal you will feel full and satiated
  • You will no longer suffer carbohydrate and junk food cravings
  • You will lose that tired feeling after lunch
  • You will have increased exercise endurance
  • You will have increased energy levels
  • You blood pressure will be lower
  • Your resting heart rate will be lower
  • You will sleep better, deeper and longer
  • You will be less prone to dependent edema
  • You will be burning fat and losing fat
  • Intermittent fasting will become easier

How to fat adapt

There is nothing really complicated about fat adaptation, when you understand the basics. Once you can fat adapt, you can do intermittent fasting and you can choose your weight and stay at that weight. What you mustn’t do is confuse uncomplicated with easy . I can tell you honestly, I found it pretty rough! Really rough for the first week, quite rough for the second and then saw light at the end of the tunnel by week 4. I really started to feel better by weeks 7 and 8 and had the benefit of having lost nearly 10 kg by this stage. It was quite remarkable. It is quite simply the best thing I have ever done for myself and Monique feels exactly the same. But ask your loved ones to support you as you get irritable and irrational. Some people get flu like symptoms. Some stomach upsets, others brain fog and sleepiness. It will be worth it. And if you fail, dust yourself down and start over.

Top Tip

If you fail, dust yourself down and start over

The time period involved is highly individual, but the first phase will take between 2 and 4 weeks. It really does vary widely. It is very dependent on your current lifestyle, dietary habits and current fitness. If you have never fat adapted and are totally reliant on carbohydrate fueling, it will take considerably longer than someone who is accustomed to using the fat fuel system intermittently.

The whisperer plan takes you through a detailed 12-week plan to allow you to change from fat fuel inhibition to fat adaptation. The plan is divided into three four-week blocks, starting with a keto diet, then intermittent fasting, thus increasing FastSpan and decreasing EatSpan. At the end of the plan, you will be able to fast for prolonged periods. If you carry on with intermittent fasting indefinitely, and we certainly do, fat adaptation continues to improve for many months and gradually you will be able to fast for longer and longer with little or no effort. Think of it as a training program for life, for health and wellness.


For most people, we advise no alcohol during the first 8 weeks of the program. But that can be a bridge too far for some. So, we have some general advice. Try to drink alcohol that is low a carb drink and drink only in the evening. Or lunch time, if that is your routine. Alcohol is a toxin and so your liver will deal with this as a priority and forget about the fat burning. Even so, we are realists and if you do drink, and you can’t stop, we suggest the following in order of preference .

  • Vodka with ice and a slice mixed with zero calorie sparkling water
  • Gin with ice and a slice mixed with zero calorie sparkling water
  • Gin or vodka with low calorie, or zero calorie tonic
  • Gin or vodka with naturally low-calorie tonic, but watch the carbs
  • Red wine
  • Dry white wine
  • Champagne
  • A splash of bitters can be welcome
  • A slice of lime or lemon can be welcome
  • Any high alcohol content shorts are OK too


Alcohol will slow down your fat adaptation and make it more difficult. Alcohol will be much more potent during and after fat adaptation, so your tolerance will be way down. And, you will be prone to very uncomfortable hypos the day after drinking, particularly after heavy sessions.

Top Tip

Alcohol will slow down your fat adaptation and make it more difficult


  • Humans have a dual fuel system; we can fuel using either fats or carbohydrates
  • Fat burning is prevented in the presence of insulin
  • ood, by stimulating insulin secretion, prevents fat burning
  • The degree to which food turns off fat burning is related to the amount of insulin it produces
  • Carbohydrate diets, in particular those with refined and super-refined carbohydrates switch off fat burning as a fuel
  • Eating carbohydrates, not fat is what makes us fat
  • Eating fats, allows subsequent fat burning and allows us to lose fat
  • Fat fuel inhibition reflects the inability to use the fat fuelling system
  • Fat fuel inhibition reflects our body’s addiction to carbohydrates
  • Fat fuel inhibition can be reversed
  • Fat adaptation is the secret to loosing fat
  • Fat adaptation has two phases; a keto diet followed by intermittent fasting
  • Fat adaptation, while simple to follow, is not easy
  • In the early stages of fat adaptation, you may find irritability, mood swings, brain fog and flu-like symptoms. These settle completely once you are fully fat adapted
  • The time required for fat adaptation depends on your diet, fitness and lifestyle
  • Fat adaptation is the secret to loosing fat and successful intermittent fasting

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