Intermittent Fasting for Fat Loss

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Last updated on July 21, 2023

Fasting is the oldest nutritional intervention for weight loss and good health that exists. Only in the last few years, however, has it gained mainstream traction. Today, fasting, in the form of intermittent fasting, is one of the most popular dieting choices on the planet. The reason is simple – it works! In this article we investigate what intermittent fasting is, why you should do it and how to implement it into your life.

What is Intermittent Fasting

Intermittent fasting (IF) is a strategic period of non eating for health and weight loss benefits. There are all sorts of intermittent fasting protocols based on the length of the eating and non-eating periods or ‘windows’. The most common are:

  • 16 / 8 – The 24 hour day is divided into 16 hours of not eating and 8 hours of eating.
  • 24 Hour Fast – on this plan you eat normally for 5 out of 7 days. On the other two, you fast for 24 hours. These are done on no-consecutive days.
  • 36 Hour Fast – A 36 hour fast usually runs from after dinner on Day One (around 7pm) right through to breakfast time on Day Three (around 7am).

What Intermittent Fasting Is Not


Starvation is dangerous. Intermittent fasting, however, is not starvation. It is simply increasing the gaps between meals in order to benefit from the body’s physiological response.

A common belief is that extended periods of non-eating will result in low blood sugar, leading to a hypoglycemic state. When you’re in that state you feel weak, faint, and unable to focus. It induces an overwhelming desire to load your body with simple carbohydrates. Yet, there is no medical proof to back up that assertion.

Going without food for a few hours will not cause your blood sugar levels to go through the floor. Sure, your insulin levels will be low. But that’s when it’s counter, glucagon steps up to release stored glycogen into the bloodstream.

Nor will Intermittent Fasting cause you to lose muscle tissue. The more muscle mass we have on our frame, the more calories we need to maintain that muscle mass. Fasting is actually a superior way to ensure that you keep that muscle mass than the traditional calorie restricted diet.

The reason?

Fasting triggers the release of growth hormone. Growth hormone is essential for muscle mass. Artificial versions of it form the basis of many anabolic steroid compounds. It encourages the body to look for other sources of fuel, such as your fat stores, rather than attacking its muscle stores.

In a study conducted by researchers at Intermount Medical Centre in Utah, study participants fasted for 24 hours and then had their Growth Hormone levels checked. At the end of the fast, the average Growth Hormone level had gone up by an amazing 1,300 percent in women and an even more staggering 2000 percent in men.

Growth hormone and insulin are like oil and water. They don’t mix. When one is high, the other disappears

Fasting preserves your muscle in another way. It is thought to aid in maintaining the level of the hormone insulin-like growth factor (IGF-1) in the body. IGF-1 helps muscle to build protein.

Intermittent Fasting Benefits

The main goal of intermittent fasting, and the reason that most people do it, is to lose body fat. Body Fat is nothing more than stored energy. When we are not fasting our bodies use glucose as our energy source. That comes from carbohydrates. However, when we are fasting, we cut off the glucose supply.

The body only has a limited capacity to store glucose. After 10-12 hours of not eating, those stores will be used up. At that point, your body will have no choice but to turn to your stored body fat in order to meet its energy needs. When it does, everything you do, both consciously and unconsciously, is eating away at your stored body fat.

But losing body fat isn’t the only benefit of intermittent fasting. Here’s an overview of how intermittent fasting will benefit you.

IF Burns Fat

Every time we eat, we are putting sugar into our system. That sugar is transported to the liver to be broken down into glycogen. If we eat too much sugar, out liver’s glycogen stores fill up. What then happens to the glycogen?

It gets stored as body fat.

If you continue taking sugar into your body, your liver stores will never get depleted and you will continue storing the excess as fat. If, however, you cut the supply, your liver’s glycogen stores will deplete to the point that the body is forced to rely on its back-up stores that are located in your fat cells. When that happens you will be burning off body fat.

Intermittent fasting set that process in motion.

You may also be interested in our article intermittent fasting muscle gain.

IF Detoxifies

Irradiating, bleaching and heating our foods has stripped it of health giving vitamins, enzymes, fiber and minerals. The processed foods that we over indulge in have clogged up our intestines, making it terribly difficult for the body to efficiently absorb the limited amount of vitamins and minerals that it does get.

The toxins that are stored inside of you are overwhelming your body.

The reasons that most people are not properly digesting their food is that they:

  • Don’t drink enough water
  • Eat too fast
  • Don’t chew thoroughly
  • Don’t eat the foods that they need to produce digestive enzymes
  • Eat processed foods that contain toxins that are hard to remove from the body

If we can’t digest food properly, we are unable to digest the nutrients that we need to fuel our body. Undigested food leads to a build-up of mucus which, in turn, makes it hard to digest nutrients.

According to Norman W. Walker D.Sc., Ph. D in his book Colon Health: The Key to a Vibrant Lifethe elimination of undigested food and other waste products is equally as important as the proper digestion and assimilation of food.  Infirmity and sickness, at any age, is the direct result of loading up the body with food, which contains no vitality, and at the same time allowing the intestine to remain loaded with waste matter. “


Here are just three examples of the damage that is being done:

Polychlorinated Biphenyls (PCBs)


PCBs are synthetic compounds that are used in insulating materials and coolants. As a result of either waste dumping or air pollution, PCBs get into our food chains. They enter our water -ways and settle on our crops.

The US National Toxicology Program have concluded that PCBs are reasonably likely to cause cancer in humans. They also cause severe acne, rashes and eye irritation.

Bisphenol A (BPA)


BPA is a carbon based synthetic compound that is used in many plastic products, such as water bottle and food containers. When it enters the human body, BPA acts an imitator of the female hormone estrogen. It has been linked to heart disease, diabetes and liver disease. BPA is especially harmful to infants and young children, as it affects brain and hormonal development.

Butylated Hydroxytoluene (BHT)


BHT is a synthetic compound that is added to foods and chemicals to prevent oxidation and enhance the color and flavor. It is also used in jet fuels, embalming fluids and petrol products. BHT has been linked to liver and kidney damage, an impaired immune system, behavioral abnormalities and cancer.

When you go on a detox, you are providing your body with the breathing space to get rid of built up toxins. Intermittent Fasting allows your body the time to detox.

Think about when you want to clean your oven. You’re not going to get in there and clear out all of the built up grease and grime while you’re cooking a roast chicken. Rather, you’ll do it at a time when the kitchen is not being used. Otherwise, it simply won’t work.

It’s the same thing with a detox. For it to work, you need to give your system a break from digestion so that it go about cleaning itself out.

Intermittent fasting allows you to do that.

IF Makes You Healthy

Intermittent fasting has remarkable curative ability. It will provide the means to cleanse and clear out your system, in the process removing the causes of a whole host of diseases from the body. And, unlike the medications which physicians typically dole out, it does all of this without posing harmful side effects. How can fasting do what medical science is unable to?

The healing secret of fasting is its ability to de-stress the body. Fasting gives your body a chance to take a break and catch its breath. After all, more than 70% of your daily energy expenditure goes to activities like digestion and detoxification. The more we eat, the more we put pressure on the body to continue on this treadmill. By jumping off the treadmill, we give the body the chance to more effectively get rid of toxins.

Fasting gives the body the opportunity to do a self-management assessment. It identifies areas of damage and eliminates them in favor of new, healthier cells.

IF Promotes Longevity

Scientists have conducted a number of studies with animals (mice and monkeys, among others) which show a clear link between fasting and living longer. It all has to do with the hormone insulin-like growth factor (IGF-1). Fasting results in lower levels of IGF-1. IGF-1 happens to play a large part in the host of diseases associated with aging.

IF Control Blood Sugar

Insulin signals your body to store energy so it can be used later. Every time we eat we release insulin. When you practice intermittent fasting, however, you receive an insulin spike after eating, but then, because you have a large gap before your next meal, there is no insulin activity going on in the body at all. This encourages the body to burn fat, while also maintaining the body’s natural sensitivity to insulin.

IF Makes You Smarter

There is promising research indicating that fasting may help to protect against such brain diseases as Alzheimer’s and Parkinson’s Disease. This research has only been done on mice to date.

In a 2012 study, conducted by the US National Institute of Aging, fasted mice were shown to more easily remember their way around a maze than fed mice. When their brains were scanned, it was revealed that the fasted mice had more new brain cell growth. There is now enough promising research on mice to merit human research.

Time-restricted Eating vs. Fasting

Fasts that last for 24 hours or less are more accurately called time-restricted feeding because the focus is on consuming all meals within a certain time window. Some people loosely refer to this style as the “feast and fast,” with the term “feast” suggesting a no-holds-barred approach to what’s consumed, as long as it’s within a certain time frame.

Intermittent fasting, on the other hand, involves more consciousness about the food consumed, although this largely involves time-restricted eating as well. People doing IF ideally should also consider the nutritional value of their meals, which is why they often follow a certain diet style like paleo or keto.

The most common description of the 16/8 or Leangains diet that people use would categorize it under time-restriction eating since they refer to it as “eating whatever you want for 8 hours and then sticking to no-calorie beverages during the 16 hours”. But if you want to realize the optimum effects of such a diet, here are some guidelines you can follow.

How to Get Started With Intermittent Fasting

Getting started with intermittent fasting is as easy as cutting out your breakfast. Contrary to what we’ve been told, breakfast is not the most important meal of the day. If your last meal in the evening was concluded at 7pm and you skip breakfast to have your meal of the following day at 11am, then you have just completed a 16/8 fast.

Once you get comfortable with 16/8 dieting you can begin to extend the length of your fast.

A big mistake that many people make is to eat a huge meal when they come off the fast. This will only make you feel sick. The key to success is to eat normally during your feeding window. Be sure, too, to drink 8-10 glasses of water while you are fasting.

Focus On What You Eat More Than When You Eat

One of the reasons why the 16/8 intermittent fasting style is popular is because it’s the easiest to adapt to people’s existing lifestyles. However, if you become careless about what you eat, you might end up not losing at all.

This is because when you’re in the “fasting” state, especially if you’re not exercising at all, your body relies on your basal metabolic rate (BMR) to burn fat. The more muscles you have, the more fat you burn. Being careless about food choices can lead you to consume more carbs or sugar and not enough protein or fat, which could lead to muscle loss and result to less capacity to burn body fat.

Intermittent fasting dictates “eating to satiety” or eating until you’re full, but make sure you’re not simply stuffing your body with empty calories or unhealthy fat that will do more harm than good.

Plan For The Long Haul

What causes most diets to fail are exorbitant expectations and a harsh reality check. New followers of intermittent fasting usually join in for the promises of “fast and easy weight loss.” But if you treat this as something temporary, a small snag can easily derail you.

Committing to better health involves a lifestyle and mindset change. Once you’ve set your mind to do this for the rest of your life, intermittent fasting will become simply one of your habits and not a chore you have to adhere to. Set your sights for the long haul and you’ll have better chances of reaching your health and weight loss goals.

How Keto Can Supercharge Your IF Efforts


While intermittent gives a sturdy structure that maximizes your body’s fat-burning time, applying the keto principles during your eating window can help you fast-track your way to a leaner body. With the number of other diets out there, why should you go for the ketogenic diet? Here are the top 3 reasons:

1.   Stabilizes Your Energy Level

The reason why you get lethargic after meals is the dip in your blood glucose level. Here’s a harsh truth: sugar is addictive. When you eat sugary food, your blood sugar level spikes as if you’re on a high.

Since most people’s default diet is composed of large carbs, and given that carbohydrates are metabolized into glucose, which is the form of blood sugar our body uses for energy, we get an energy boost after eating sweet or starchy things. But our bodies can only convert a limited amount of sugar into glucose. The remaining ones get stored as fat instead. When this happens, the sugar high is followed by a huge crash, leaving us sluggish, our brains foggy, and with more unwanted fats.

The keto diet, on the other hand, is designed to switch our bodies from burning sugar to burning fat for energy. Fat is a cleaner fuel source, and if you have an excess of that, then you’ll hit two birds with one stone – decrease your fat stores and have a steady supply of energy!


2.   Keeps You Full For Longer

Unlike carbohydrates, protein and fat are macronutrients that keep you sated for longer. The ideal ketogenic meal is composed of 70-75% healthy fat, 20-25% protein, and only 5-10% carbohydrates.

 Although the general rule states that you “eat until full” without mentioning calorie requirements, ideally, you shouldn’t go below 1,000 calories per day. Any less than that and your body will go into starvation mode, which will make it hold on to fat more.

3.   Major Fat Burn

As we mentioned, the ketogenic diet makes you burn fat for energy instead of glucose. In a normal carb-heavy diet, during the fasting time in IF, your body would simply be burning off the carbs that you ate within the window, leaving your excess stored fats largely untouched especially if you don’t exercise. But if you consume keto meals during your feast time, your body will be left with nothing but fats to burn during fasting hours, resulting in more efficient fat burning.

12 Ways to Do Intermittent Fasting

Today there are a number of different fasting methodologies. Finding the one that is best suited to your goals and lifestyle requires knowing what your options are. Here are the 10 most popular forms of intermittent fasting being used by people to make extraordinary body transformations.

24 Hour Fasts (eat-stop-eat)

The eat-stop-eat method of Intermittent Fasting involves eating normally for 5 days out of every 7. You eat in a healthy manner but are not required to count your calories or reduce meals. On the other two days you technically eat no food whatsoever.

In reality, however, your 24hr fasting periods will run over a 24 hour period that does not align with midnight. As an example, you may stop eating at 7pm one night and then fast through until 7pm the following night. So, on day one, you eat before 7pm and on day two, you eat after 7pm.

Some people prefer to do their two day fasts over the weekend, which allows them to eat normally during the work week. Others plan their fasting days to coincide with their no workout days. This would allow them to get nutrients in before and after their workouts.

16/8 (Lean Gains)

The 16/8 version of Intermittent Fasting involves fasting for 16 hours each day and eating during the other 8 hours of every 24 hour period. This is a flexible protocol as you are able to tailor your fasting and feeding windows into what time slots that suit you. Regardless of what times you choose, you will find that a large chunk of your fasting time will be during the hours of sleep.

For many people, adjusting to a 16/8 plan simply requires them to skip their breakfast. As an example, if you had your last meal at 7pm, then you need to fast through until 11am the next day, which skipping breakfast would accomplish.


The next step on from the 16/8 diet is the 20/4 diet. As the name suggests, this involves fasting for 20 hours of each 24, with a 4 hour eating window. There is a substantial amount of research to suggest that prolonging your period of fasting to up to 20 hours promotes greater fat loss  and growth hormone release.

It is important to note that you should avoid the tendency to gorge during your eating window. The aim is not to ‘make up for’ the calories you didn’t get during your fasting period. Instead, you should aim to eat as you normally would when not fasting during your eating window.


OMAD stands for one meal a day. It is also known as the 23:1 Diet. It involves fasting for 23 hours each day and eating for one hour. Outside of that single hour, you do not eat any food or consume any beverages that contain calories. Within your one hour eating window there are no restrictions on what you eat. Of course, it will be far better for a person’s overall health to eat healthily during this time.


The 5:2 diet is known as a modified fasting program. It involves eating ‘normally’ for five days of the week (usually Monday through Friday) and then restricting your caloric intake to just 500 per day for women (600 calories per day for men) on the other two days.

The two days of restricted eating do not have to be consecutive. The evening before the first restricted calorie day, you should finish eating at 8pm. The following morning you will have a light snack for breakfast (average 300 calories) and then eat nothing throughout the day, have a similar small 300 calorie snack that evening. The foods that you eat should be low on the glycemic index so as to not to spike your insulin level.

With the 5:2 Diet you never go a full day without eating. You also have the flexibility to select which days of the week you fast. However, because you are not going completely food free, you will still get an increase in blood sugar levels. As a result, you will not lose fat as quickly as if you were to go on a full fast. Some people also find that eating a small meal of five or six hundred calories actually makes them feel hungrier than if they hadn’t eaten at all.

36hr Fast

A 36-hour fast diet involves not eating for one complete day. As an example, you begin the fast after your dinner meal at 7pm on Day One. You then go through the entire next day with no food. After sleeping on an empty stomach, you begin eating again at 7am on Day Two. This gives you a 36-hour period of fasting.

Longer fasts, such as this one, will speed up all of the benefits that come from fasting that we discussed in the previous chapter. However, they will also increase the risks. Longer fasts may make some people feel sick, nauseous or head-achy.

42hr Fast

The 42-hour fast is a progression fast for people who have begun with the 16/8 diet, moved on to the 36-hour diet and then want to extend the benefits even further.

On the 16/8 diet, many people replace their normal breakfast with a glass of water and maybe a cup of coffee. With a 42- hour diet, you stop eating in the early evening of Day One (let’s say at 6pm). You then fast through all of the next day and through the night to 6am on Day Three. At this stage, you have been fasting for 36 hours. However, rather than breaking the fast, you simply have your breakfast replacement of a glass of water and/or coffee and then continue to fast for another six hours. You have your first meal at 12 noon on Day Three, to complete 42 hours of straight fasting.

You may also want to read our article coffee and intermittent fasting

Fasting Mimicking Diet

The Fasting Mimicking Diet is a modified form of intermittent fasting that allows you to eat small amounts of food rather than completely abstaining as you would on an IF diet. The diet lasts for five days and is done on a monthly basis. During the five days, you consume 40 percent of your normal caloric intake. It is claimed that the traditional form of intermittent fasting can be harmful because it does not provide you with a regular flow of electrolytes and nutrients.

The fasting mimicking diet is designed to trick your body into thinking that it is going on a diet in order to reap the benefits of fasting without totally restricting your caloric intake.

There are a number of commercial fasting mimicking diet products available that provide you with a full-5 days of food products. Here is an example of a day’s worth of fasting mimicking foods:

Breakfast: Tea and a nut butter

Lunch: Small serving of vegetable soup and a few kale crackers

Snack: A handful of olives

Dinner: Small bowl of soup

Protein Sparing Modified

A protein sparing modified fast (PSMF) is a very low-calorie diet that is designed to ensure that a person does not lose muscle mass while shedding body fat. There are two phases to the diet. The first is an intensive phase lasting 4-6 months in which calories are severely limited.

The second phase is a refeeding period during which calories are gradually increased back to the pre-diet level. This phase lasts for 6-8 weeks.

During the intensive phase, the calories are reduced to around 800 per day. There is a focus on lean protein food sources such as chicken breast, egg whites and fish. The person should aim for 1.2-1.5 grams of protein per kg of bodyweight. The diet also allows for between 20-50 grams of carbohydrates per day. The only fat consumed is that which comes naturally with the proteins consumed.

During the refeed phase, fat and carb calories are gradually brought back in while proteins are reduced.

Fat Fasting

The Fat Fast Diet is a short-term intervention designed to help people who are not losing weight to overcome a plateau. It involves dramatically increasing fat intake for three to five days. It is commonly used by people who have been following a low carb or keto diet.

The Fat Fast Diet involves eating a thousand calories per day. This is around half the daily caloric recommendations of the American Dietetic Association. Nine-hundred of those calories come from fat, with the other hundred coming from carbs and protein. These calories are divided between 4-5 mini meals over the course of the day.

Dry Fasting

Dry Fasting is a type of fast that does not permit the drinking of water during the fasting period. This is an advanced method of fasting that should only be practiced by people who are experienced fasters. Dry fasting can be done on any version of a fasting diet. It is believed that dry fasting will accentuate benefits of regular fasting.

Juice Fasting

Juice Fasting, also known as Juice Cleansing, involves consuming nothing but fruit and vegetables juices, with no solid calories being taken into the body. It is widely used for detoxification purposes.

The Juice Fast involves consuming fruit juices and broth. These meals are spread evenly over the course of the day. A couple of sample juice recipes follow:

Pineapple and Pear (Serves 1)

1 pear, cored and quartered

1 apple, cored and quartered

1 slice of pineapple, peeled, including the core

Put all ingredients through an electric juicer, then serve

Veggie Apple (Serves 1)

½ small cucumber

4 carrots, unpeeled

2 celery sticks

1 apple, cored and quartered

Put all ingredients through an electric juicer, then serve

The Juice Fast normally lasts for five days. You can, however, stop any time short of that if you wish. Often, Juice Fasts take place over a weekend, when people have more time to prepare and enjoy them.

You may also be interested in our article on intermittent fasting drinks.

Wrap Up

If you haven’t yet given intermittent fasting a try, why not use this article to spur you on to give it a go. You will be surprised at how easy it is – and how ‘not hungry’ you feel. Stick with it for at least six weeks to start seeing some real results in terms of fat loss and overall health. Then, if you’re like most people who dip their feet in the intermittent fasting waters, you’ll be a lifelong IFer.

For more fitness information to help you achieve your go to our home page Smart Fitness Results.

Steve Theunissen has qualified from the International Sports Sciences Association (ISSA) and is a certified Personal Trainer and Nutritionist. He has over 30 years experience in fitness and nutrition and currently working with famous fitness professionals. He is currently living in New Zealand with is wife and daughter.

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