Nutrition | Marty

Low Carb Intermittent Fasting is a combination of Low Carb Diet ( LC) combined with Intermittent Fasting ( IF). When combined with a Caloric Deficit it forms a particularly powerful approach to weight loss that offers a number of advantages over a regular weight loss diet.

LCIF can help anyone lose weight and get in shape.

I’ve used it for over 5 years to stay in shape and in that time have helped many others. But it's fair to say without knowing the basics there’s a lot that can easily be misunderstood which take you off track.

So, If you don’t know anything about Intermittent Fasting, Low Carb or Caloric Deficit, we've got you covered. In the following article, I’m going to explain the concept, the benefits, show you how to get started with a practical example and dispel a few myths along the way. 

What is Low Carb Intermittent Fasting?

Firstly, let's clear up something most people get wrong right from the start. LCIF isn’t a magic bullet for weight loss on its own.

I know it’s easy to get the wrong idea, there’s a lot of talk about the benefits of Intermittent Fasting and Low Carb diets in general but the fact is to lose weight the human body must be in a caloric deficit.

What Is A Caloric Deficit?

This occurs when you are consuming less energy from your intake of food (Calories) than your body requires in total energy (Calories, again) to maintain current weight. The end result is weight loss.

If Caloric Deficit Is The Key To Weight Loss Why Bother With LCIF?

There’s a couple of reasons for this. And, while there are conflicting opinions on just what the most beneficial aspect of LCIF is, one of the most compelling is the following:


Our food can typically be broken down into three specific groups, known as Macronutrients. These are known as Protein, Carbohydrates, and Fat.

In very simple terms, Proteins can be looked at as the building blocks of the body. They are used to build and repair tissue, make enzymes and hormones. Fat is used to store energy in the body and assist with chemical processes.

Carbohydrates on the other hand are our primary energy source.

Pasta - Carbohydrates

The role of carbohydrates

Once consumed Carbohydrates are broken down into Glucose in the bloodstream. Excess Glucose is converted into Glycogen (the stored chain form of Glucose) and stored in the muscles and liver; it's then broken down to Glucose again as required by the body for energy.

In an average person the liver can hold 100 Grams of Glycogen while our muscles can hold approx. 500 Grams.

This is where things get interesting....

Excess Glucose that cannot be stored in the muscles or liver is converted to Lipids (Fatty acids) and then stored as body fat. This process is called lipogenesis and occurs thanks to the hormone Insulin. If consuming a Low Carb diet, there is a reduced Insulin response as there is less Glucose in the bloodstream that has the potential to be stored as body fat.

If the body has insufficient Glucose to draw upon for energy it will begin to convert stored body fat as an energy source through the process of Ketosis. The ‘Ketogenic Diet’ diet also utilises a very low Carbohydrate approach.

Importantly, the longer the body becomes accustomed to converting fat for energy as opposed to sugar, the more efficient it becomes at it. You could say by following a Low Carb diet you are essentially training your body to become better at burning body fat.

What Is Insulin?

Insulin is the hormone that is responsible for removing excess Glucose from the bloodstream. It is produced by the Pancreas. Type 2 Diabetics suffer from Insulin resistance often (but not always) due to an unhealthy lifestyle e.g. an unhealthy diet, high in sugar combined with a sedentary lifestyle. The body becomes resistant to Insulin and high levels of Glucose remain in the bloodstream.

Type 1 Diabetics, on the other hand, do not produce Insulin or produce an insufficient amount due to an autoimmune condition which destroys the cells of the Pancreas. 

Both groups require Insulin supplementation.

Calorie Control

The second and for some even more compelling reason LCIF is effective is Calorie control.

When undertaking Intermittent Fasting your window for consuming food is narrower than the standard 12-14 hours most people operate within. This approach tends to lead to a natural reduction in caloric intake as most people simply cannot consume as much food as they would throughout a standard day within this smaller period of time.

Combine this with the fact that limiting Carbohydrate intake generally means increasing your Protein intake (Protein is more satiating than Carbohydrates) and many people find it easier adhering to an LCIF diet.

Beating The Sugar Crash

Refined Carbs - Sugar Spike

Alternatively, if consuming a diet high in processed Carbohydrates fibre is stripped from the food, resulting in the body digesting processed Carbohydrates quickly, leaving you feeling hungry sooner.

It’s also true that highly processed Carbs lead to a rapid Insulin response due to the high sugar content, this process can result in low blood sugar (also referred to as a sugar crash) which signals the body to consume more food by making you feel hungry.

Low Carb Intermittent Fasting Results

So does LCIF help you lose weight?

In short, yes. It has a proven track record and you won't find many people arguing that it doesn't work, regardless of whether the main perceived benefit is simply Calorie Control.

Will it work for you?

The best weight loss methods are the ones we can sustain. Can you sustain an LCIF approach to weight loss?

Most people report some hunger early on and depending on how much you reduce your Carbohydrate intake you may experience what is known as ‘low carb flu’. But as the body adjusts the hunger pains and flu-like symptoms diminish making it far more sustainable for most people.

What Is Low Carb Flu?

When the body transitions from using sugar (Glucose) as energy to fat it's quite normal to experience flu-like symptoms as the body adapts. These symptoms include but are not limited to fatigue, an inability to focus, headaches, muscle aches and in some cases nausea. While some experience quite severe symptoms, the majority of people will only suffer from a mild reaction or no reaction at all. Symptoms typically last between 5 - 10 days.

Is Low Carb Intermittent Fasting Safe?

It is safe. But there are a few things you need to be aware of before starting:

  • Eating Disorders

If you have experienced an eating disorder in the past such as Anorexia or Bulimia, any form of fasting should be discussed with your doctor and in many cases avoided. The fast/feast mentality can have a psychological impact and push someone towards a pre-existing eating disorder.

  • Overeating and Weight Gain

You must make sure you are not overeating during the eating window. Just because you fasted for 16 hours doesn’t mean you can eat everything in sight during the eating window as you will put on excess weight if in caloric surplus.

  • Maintaining A Balanced Diet

You must ensure you maintain a balanced diet. Changing the way we eat can sometimes force changes we might otherwise not consider. Always focus on a healthy balance and consuming plenty of vegetables.

  • Caffeine Dependency

Black coffee is often associated with Low Carb Intermittent Fasting and is perfectly acceptable during a fasting period due to its lack of calories (2 calories per cup). Some people may rely on this a little too much however and take in too much caffeine. Excess caffeine can be detrimental to sleep and cause health issues such as:

  • Dehydration
  • Dizziness and headaches
  • Insomnia
  • Irregular heartbeat

I’d also recommend the following groups of people seek professional medical advice before undertaking LCIF:

  • Diabetics
    While LCIF may have benefits for Diabetics it is strongly advised to speak to your doctor before undertaking any major change to your diet.
  • Mum’s to be
    Studies have demonstrated that pregnant women who fast may have issues with their children’s development, both physically and cognitively.

How to Get Started on an LCIF weight Loss Diet

Step 1) Introduction to Intermittent Fasting

For the purpose of this guide, I’m going to recommend starting with a variation of the 16:8 approach to Intermittent Fasting.

The truth is there are a number of different approaches to intermittent fasting that you can read more about here. But in the majority of cases the 16:8 method (Fasting for 16 hours and consuming your food in the 8 remaining hours) would be considered the easiest method for beginners to adjust to.

But I don’t recommend coming out of the blocks on day one with a 16 hour fast. Intermittent Fasting can take time to adjust and therefore I recommend a 12 hour fasting window to begin with before increasing the fasting window to 16 hours.

A simple and practical way to get started is to simply skip breakfast.

The most popular approach to the 16:8 diet is to consume your calories between midday and 8:00pm, however, this can be difficult when starting out so instead allow yourself to eat as you normally would in the evening for the first 1-2 weeks before gradually reducing this to 8 pm.

For shift workers you may need to alter this schedule to suit your work schedule however the concept remains the same. Stop eating before you go to bed and do not consume calories until you normally would have your second meal of the day.

Isn’t Breakfast The Most Important Meal Of The Day?

Disregarding for a second the fact that most people do not consume a healthy breakfast to begin with e.g. most breakfast cereals are high in sugar. The truth is there really is no reason you can't skip breakfast. There is also no evidence that suggests eating breakfast is beneficial with regard to weight loss or improved Metabolism.

Step 2) Combining Low Carb and Intermittent Fasting

Once you have established your fasting window it is time to factor in the number of calories you will consume from Carbohydrates. But first, let's dispel a few commonly held beliefs about Carbohydrates.

In Defence of Carbohydrates

Carbohydrates from Vegetables

Carbs get a pretty bad rap in today’s nutritional landscape but the fact is nothing about nutrition is ever that simple and not all Carbs are created equal. When we mention Low Carb Diets it would perhaps be ,more accurate to refer to Low (processed or refined) Carb Dieting, but to be fair it just doesn’t have the same ring to it.

In any case, Carbohydrates from cruciferous vegetables, sweet potato, brown rice, nuts, beans and many fruits should not be avoided and in fact contain many of the micronutrients our bodies requires to remain healthy.

Refined carbs on the other hand such as white bread, pasta, soda drinks, and cakes and biscuits are best avoided and are in large part responsible for the obesity epidemic we are witnessing along with lack of sleep and a more sedentary lifestyle.

How Many Calories Should I consume from Carbohydrates?

There really is no magic number that applies to everyone when discussing Carbohydrate consumption and it can largely depend on your Somatype.


What’s a Somatype you ask? 

While not an exact science, we can place most people into three specific body type groups:



Naturally Thin



Naturally Athletic



Naturally Thickset

Depending on your goals (in this case weight loss) its best to adjust your Carbohydrate intake to suit your somatype as each of the body types listed have different Carbohydrate tolerances.

For instance Endomorphs tend to store more body fat and have a larger bone structure, whereas Mesomorphs are more naturally athletic and tend to have a faster metabolism. Ectomorphs on the other hand are naturally skinny and find it difficult to gain weight.

Below is our recommended macronutrient ratios based on your Somatype:






















Depending on your body type, you may have different tolerances when it comes to Carbohydrates and low carb dieting.

In the majority of cases Ectomorphs and Mesomorphs are less interested in weight loss and tend to tolerate higher amounts of Carbohydrates in their diet with less body fat gained. The macronutrient ratios recommended above for these body types would not reflect a low Carbohydrate diet.

Step 3) Incorporate a Caloric Deficit

Once you have established your eating window and Carbohydrate intake you can start calculating your Caloric Deficit. 

Don’t Go To Extremes

Studies demonstrate that eating too little e.g. creating an excessive caloric deficit over an extended period will only serve to slow your metabolism and ultimately your progress if trying to lose weight.

Your body might just be the most complex thing in the entire universe (yes, it’s true) and it helps to remember that it is always trying to reach a state of equilibrium (Homeostasis) and will make adjustments to any form of caloric restriction by altering your metabolism. Therefore when approaching weight loss in a practical sense, slow and steady is always the most effective approach.

BMR - Basal Metabolic Rate

To calculate a caloric deficit we need to do some math. Specifically, we need to know our Basal Metabolic Rate, otherwise known as our BMR. This number indicates the total number of calories our bodies require each day to maintain current weight, taking into consideration our gender, age, height starting weight and activity levels.

The formula most often used to calculate this total is known as the Harris–Benedict equation which is as follows:



BMR = 66.5 + ( 13.75 × weight in kg ) + ( 5.003 × height in cm ) – ( 6.755 × age in years )


BMR = 66 + ( 6.2 × weight in pounds ) + ( 12.7 × height in inches ) – ( 6.76 × age in years )



BMR = 655.1 + ( 9.563 × weight in kg ) + ( 1.850 × height in cm ) – ( 4.676 × age in years )


BMR = 655.1 + ( 4.35 × weight in pounds ) + ( 4.7 × height in inches ) - ( 4.7 × age in years )

Don't feel like doing all the math yourself? Don't worry. I've included a free calculator below that calculates your BMR, established your Caloric deficit and even works out your required amount of Protein, Carbs and Fat.

Deliberate Exercise

Once we have an established BMR it’s simply a case of increasing this total amount to take into account your current activity levels (calories used by the body during deliberate exercise).

I’ve listed the level of activity beside the amount you should increase your total BMR below.

Activity Levels

Completely Sedentary

Multiply your total BMR by 1.2%

Light Active
(light exercise 1-3 times per week)

 Multiply your total BMR by 1.375%

(moderate exercise 3-5 times per week)

Multiply your total BMR by 1.55%

Very active
(heavy exercise 6-7 days a week)

Multiply your total BMR by 1.725%

Extremely active
(very heavy exercise 6 - 7 days per week)

Multiply your total BMR by 1.9%

Once you have factored in your activity levels the next step is to reduce your total BMR by your chosen caloric deficit.

The Ideal Caloric Deficit

It’s best when considering your caloric deficit to calculate in percentages. For most people a good starting point is a 20% reduction in calories.

A percentage based approach is most effective because it takes into account different weight ranges e.g. the more overweight a person is the more body fat they have to lose and the less likely their bodies will consume muscle tissue while in caloric deficit.

Simply providing a number e.g. 400 calories might be effective if you are around 200 pounds but if you are much heavier, a larger deficit would be recommended, or your progress will be too slow and may affect your motivation.

Alternatively, if you are quite lean, to begin with you would definitely want to start with a lower deficit to preserve lean muscle mass.

A Practical Example

Ok, so the information above can quickly get complicated. And in some cases may put people off the idea of LCIF.

In the following section, I am going to walk you through what a typical day would look like for someone undertaking LCIF.

Establishing a Caloric Deficit

For the purpose of this example, let's consider our test subject a 42-year-old male, Endomorph weighing in at 210 LBS who is 6ft tall. The subject is mostly sedentary e.g. works behind a desk and his only form of deliberate exercise is walking his dog a couple of times each week. The subjects goals are to lose at least 20LBS of weight, predominantly body fat and become more active. 

Low Carb Intermittent Fasting is perfect for this type of goal. First let's establish the subjects BMR

BMR = 66 + ( 6.2 × weight in pounds ) + ( 12.7 × height in inches ) – ( 6.76 × age in years ) = ?

For our test subject this results in the following:

BMR = 66 + ( 6.2 × 210 ) + ( 12.7 × 72 ) – ( 6.76 × 42 ) = 1998.48 Calories

We now have the subjects BMR, which is 1998.48 Calories. Next, we need to establish the subjects deliberate exercise into the equation.

As the subject’s only form of deliberate exercise is to walk his dog 1-3 times per week, we can consider the activity levels to be light active. 

Light Active
(light exercise 1-3 times per week)

Multiply your total BMR by 1.375%

This means we only multiply the subjects BMR by 1.375 which results in a total of: 2747.91 Calories per day to maintain current weight.

Now that we have established the total calories required for the subject to maintain his current weight we simply need to reduce this by 20% to provide us a caloric intake that will result in steady weight loss.

2747.91 x .2 = 549.582 Calorie Deficit
2747.91 - 549.582 = 2198.328 Allowed Calories

We can round this up to 2200 calories for the sake of practicality.

Intermittent Fasting

This is the simple part (I said simple, not easy).

Just stop eating at 8:00pm the previous night and don’t eat again until midday the following day. In the meantime you can consume black coffee and zero calorie drinks, although remember many of these contain artificial sweeteners and additives that have a dubious record when it comes to health.

In general the occasional zero calorie drink probably won’t do you any harm but I’d recommend against relying on them too heavily or making them a normal part of your day.

Low Carb Diet

Next we can establish how many carbohydrates the subject should consume per day, taking into account the subjects Somatype.

As our test subject is an Endomorph the recommended starting point for Macronutrient ratio is as the following:







Based on our recommended caloric intake this would result in the following calories recommended for each Macronutrient:


2200 x .4 = 880 Calories


 2200 x .2 = 440 Calories


2200 x .4 = 880 Calories

Free Low Carb Intermittent Fasting Calculator

Now that you understand the general concept it's not at all that important to do the calculations listed above manually. In fact using a spreadsheet or specifically formulated calculator will save you a lot of time.

I have included a handy calculator below that calculates your BMR including deliberate exercise, desired caloric deficit and then lastly the ideal macronutrient breakdown for your body type.

Summing Things Up

In the example above, our test subject would be undertaking the following regimen:

  • No food after 8:00pm until midday the following day
  • 2200 calories allowed per day
  • 880 calories from Protein, 880 Calories from Fat, 440 Calories from Carbohydrates

While this can take some working out if new to LCIF dieting the fact is if sticking to the above our test subject would lose weight.

How much weight you ask?

1 LB of fat is approximately 3,500 calories. Therefore, if sticking to a caloric deficit of approx. 550 calories per day, we could reliably predict weight loss of more than 1lb of fat each week. No ifs or buts.

a reliable system that will lead to weight loss

Weight Loss

While many diets are little more than guesswork Low Carb Intermittent Fasting incorporating a Caloric Deficit is a reliable system that will lead to weight loss. And while there is more we could dive into including the thermal effects of food, cheat meals, micronutrients and metabolism, it is often a trap to get too caught up in these details. 

It’s always better, once you have an understanding of the concept to just begin, so my question to you is are you ready to start on a Low Carb Intermittent Fasting program and lose weight? The only thing stopping you is your ability to adhere to this approach and ultimately that will come down to how committed you are.

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