Intermittent Fasting

Wondering what intermittent fasting is all about? Check out our guide, covering what it is, the different types of intermittent fasting, benefits, risks and if it's right for you.

Did you know being in a fasted state can result in significant health benefits such as improved blood sugar levels and insulin sensitivity? Intermittent fasting is increasingly becoming the go-to for people who want to lose weight but also reap the other range of health benefits. The interesting thing about intermittent fasting is that it’s not a typical diet (which often puts your body in a state of deprivation). Intermittent fasting, rather, is a lifestyle change.

In this beginner’s guide to intermittent fasting, we’ll explain everything you need to know about the different types of fasting methods, how fasting works, and the potential benefits and pitfalls of this way of eating.

What is Intermittent Fasting?

Intermittent fasting, also known as time-restricted feeding, is a way of eating that has risen in popularity over the last few years. However, this way of eating is nothing new. Intermittent fasting has been used throughout history as a way of life to improve overall health and longevity, as well as for religious reasons such as Lent and Ramadan.

Today, fasting is a popular and suitable weight loss solution that has the power to help you rest your body and restore its true functions. However, there are also many potential therapeutical benefits of the eat-stop-eat method, with a growing body of clinical research beyond hitting your magic number on the scales and losing bodyweight, such as: increased energy, improved cholesterol levels and treatment of Type 2 diabetes.

Read more: Intermittent Fasting And Type 2 Diabetes

One of the main attractions of intermittent fasting is that it is a simple approach to eating. In fact, you already intermittently fast while you’re sleeping as you pause from eating between dinner and breakfast. The first meal you consume when you wake is breaking the fast – “break-fast”.

Intermittent fasting doesn’t focus on specific nutrients or involve eating or avoiding particular foods. Instead, it focuses on controlling when you eat and more importantly, when you don’t, through a fasting schedule.

Variations of Intermittent Fasting

There are several variations of intermittent fasting that give you the flexibility to determine which approach may help you reach your goals and suit your lifestyle. The time frame, fasting window and calorie restriction will vary from one intermittent fasting plan to another.

However, they all work on the premise of alternating periods of normal food consumption with extended periods of eating little to no food. Unlike traditional diet plans, an intermittent fast doesn’t dictate how many carbs you should eat or what foods to avoid. It’s the timing and the number of hours of fasting that’s important.

Below, we discuss some of the main intermittent fasting methods and their key features.


The 16:8 fast is based on a feeding window of 8 hours followed by a 16-hour fast. It’s generally done daily. It’s one of the most popular methods due to the relatively short fasting period and simplicity of defining the schedule of when you can and can’t eat.

On this plan, you may decide to schedule your eating window between 10:00 am and 6:00 pm and do the majority of your fasting while you sleep. Most people will eat two or three meals during the 8-hour feeding period, ensuring they eat their highest calorie meal after exercise.


The 20:4 fast, also known as the ‘Warrior’ diet, is based on the same premise as the 16:8, however, the fasting period is longer. On this plan, you’d eat one larger, nutrient-dense meal or a couple of smaller meals at the start and end of the 4-hour eating window before fasting for 20 hours.

Most people choose to schedule their food intake towards the end of the day to accommodate family mealtime, social events and after-work training. For example, you may choose to eat between 3:00 pm and 7:00 pm, starting your 20-hour fast after dinner.


Also referred to as “The Fast Diet”, on the 5:2 intermittent fasting plan you’re severely restricting your calorie intake for 24 hours at regular intervals.

By adopting the 5:2 fasting method, you’ll eat regularly for five days. This is followed by 2 days of restricting your caloric intake to typically 500 (2090 kilojoules) for women and 600 calories (2510 kilojoules) for men.

This approach became popular by scientist and journalist Michael Mosley about 5 years ago. However, more recently Mosely has adapted the diet to increase the eating restriction to 800 calories while consuming a Mediterranean-style diet on the other 5 days for optimal fat loss and health benefits.

Alternate-Day Modified Fast

Alternate-day fasting can take on several forms depending on your lifestyle and health goals. You can choose to eat during a 12-hour eating window and then fast for 36 hours. You could have an eating period of 24 hours followed by a 24-hour fast the next day. Alternatively, you could adopt the 5:2 method, however, instead of restricting your calorie intake twice a week, you would have a low-calorie day every other day.

It’s basically structured around the pattern eat-stop-eat. You would schedule one to two of these fasts a week.


It’s important to understand the risks involved in fasting beyond 24 hours, particularly for those who have high training demands or chronic health issues. We recommend you speak to your general practitioner, dietitian or nutritionist before embarking on any fast for a significant amount of time.

Extended Fasts

Extended fasts are those typically greater than 48 hours. These are not overly common as fasting for extended periods of time is difficult to do and is can have complications. If you are considering an extended fast before you stop eating, we recommended you consult a health practitioner to find out whether it is suitable for you.

Absolute fasts

An absolute fast is where you fast for a specific period of time avoiding both food and beverages including water, black coffee and tea. Typically this is done for religious reasons such as during Ramadan. It is generally not advised for weight loss or health purposes and should only be done following the advice of a general practitioner.

How Intermittent Fasting Works

Intermittent fasting is based on the simple act of abstaining from eating food for a defined period of time. The eat-stop-eat pattern allows your body to rest and reset and utilise the stored energy we’ve built up from eating in excess.

By fasting, you’re helping your body shift from a sugar-burning machine into an efficient fat-burner.

How does it work? It’s simple

When you consume food it’s readily broken down into energy available for our body to use immediately. What it doesn’t use will be stored away in the liver and muscles, or as body fat. In order to conduct this storage process, the body relies on the hormone insulin.

When you eat, insulin rises to break down the carbohydrates into glucose and store it in the liver and muscles in long chains of glycogen. When you eat constantly, these stores become full and the excess glucose is converted into body fat. Additionally, our insulin levels never fall which can cause insulin resistance and lead to conditions such as Type 2 Diabetes.

Fasting has a positive effect on our insulin levels whereby the hormone becomes most sensitive and efficiently signals the body to burn the stored energy as no energy is being supplied through food. Additionally, your levels of leptin, known as the hunger hormone, are also reduced leading to a faster metabolism.

Your blood glucose levels fall and your cells are reprogrammed to derive most of the energy first from the glycogen stores and then from fat. This not only results in weight loss, but also healthy blood sugar regulation and hormone balance.

In further detail: Intermittent Fasting And Hormone Balance

The Health Benefits of Intermittent Fasting

Abstaining from food entirely for any period of time, or severely reducing your calorie intake, offers the most obvious benefit of weight loss.

In further detail: Intermittent Fasting And Weight Loss

The effects of intermittent fasting on weight varies from one person to the next and depending on which method you choose. However, the basic principle of needing to consume fewer calories than you burn still applies if you want to avoid weight gain or shift any excess kilos and lose body fat.

There is also a growing body of evidence on the other benefits intermittent fasting may offer beyond weight. Fasting may lead to:

  • Increased fat-burning ability
  • Lowered insulin and leptin levels
  • Improved blood sugar control
  • Increased growth hormone
  • Management or reversal of type 2 diabetes
  • Improved LDL and HDL cholesterol levels
  • Increased energy
  • Increase focus and cognition
  • Increased longevity
  • Enhanced digestive function
  • Reduced inflammatory markers

In further detail: Intermittent Fasting: Tips To Starting Your First Fast

Potential Pitfalls of Intermittent Fasting

Intermittent fasting may have plenty of health benefits, but there are some possible side effects that can be experienced by fasting for long periods of time.

Some of the most common, yet short-term, pitfalls of intermittent fasting include:

  • Hunger
  • Constipation or diarrhea
  • Headaches
  • Light-headed / Dizziness
  • Fatigue
  • Heartburn
  • Muscle cramps

Severe side effects from intermittent fasting, particularly shorter or alternating fasts, are rare. These may include dehydration, refeeding syndrome or excessive weakness. If these symptoms do occur, it’s important to break the fast and resume your normal food intake and consult your doctor if they persist.

In further detail: Side Effects Of Intermittent Fasting

Who Intermittent Fasting is Not Suitable for

Intermittent fasting can be helpful for many, however, there are some people who shouldn’t adopt this approach or any other diet for that matter.

Avoid intermittent fasting if you are:

  • Underweight – below <18.5 BMI
  • Have an eating disorder such as bulimia or anorexia
  • Pregnant
  • Breastfeeding
  • Under 18 years old

Intermittent fasting should be done under the guidance of your health practitioner if you:

  • Have Type 1 or Type 2 Diabetes
  • Are anemic
  • Are on a prescription medication
  • Have high uric acid levels or gout
  • Have a serious chronic medical condition including liver disease, kidney disease or heart disease

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