top of page

How to Fast: A Beginner's Guide to Getting Started

Updated: Jan 7, 2023

Michelle McKenzie Guide to fasting - roasted pumpkin and salmon
Photo credit: The Regeneration Diet (Day 1 Dinner) Michelle McKenzie

The healing power of fasting

There are a number of reasons individuals fast, such as spiritual or religious, but the main reason, for many, is health. Fasting can be used as a treatment for metabolic disorders and as a preventive tool for metabolic health, gut health, brain health, hormone health and overall cellular health.

Our biological history

As we have evolved, the genes that regulate metabolism for nutrient usage and fat storage have remained relatively the same, but our food environment and lifestyles have changed significantly.

During our hunter-gatherer days, we went without food for extended periods of time, we had no choice, and our bodies adapted.

Today we can source and eat whatever food we want - all day and all night. The type of eating patterns we see today, alongside our genetic makeup, has created an imbalance, playing a role in the progression of chronic diseases such as obesity, type 2 diabetes, high blood pressure and cardiovascular disease.

Michelle McKenzie - nutritionist
Michelle McKenzie, Associate Nutritionist (BSc, ANutr)

Why fast

Some forms of daily fastings, such as time-restricted eating, can help to prevent these outcomes, and longer fasts are reported to potentially reverse some of these diseases.

There is a huge amount of research on fasting these days due to the multiple health benefits different fasts can generate.

Fasting triggers pre-existing information that is encoded in our genes.

“Fasting activates coordinated responses that are in tune with evolution and is one of the most powerful interventions we can rediscover to promote coordinated changes that do not disrupt the harmony of the human body” (Dr Valter Longo).

How it works

Our bodies are designed to have metabolic flexibility, smoothly transitioning between two different states: fed and fasting.

In the fed state, in response to a rise in blood glucose, insulin is released to ensure blood glucose is kept within safe ranges. It helps to transport it into our cells, where it is used as an immediate energy source.

As insulin is also known as the fat-storing hormone, any energy from the food that isn’t used is stored as excess calories in your fat cells.

Nuts  and berries, with some herbal tea, regenerative diet and fast
Photo credit: The Regeneration Diet (Day 2 Breakfast) Michelle McKenzie

Essentially, if insulin is circulating, the burning of fat is paused while the body burns glucose from your last meal or snack.

In a fasted state, the process of storing energy from food after we eat goes into reverse. Insulin and blood glucose levels drop, and stored glycogen (stored glucose in the liver) and growth hormone are utilised.

A metabolic switch is then triggered, and rather than using glucose for energy, we switch to burning ketone bodies and free fatty acids. At this point, the body can also start to use stored body fat from your fat cells and use this for energy instead of glucose.

This is why fasting can have such a positive influence on body weight.

Benefits of fasting

Fasting is reported to:

  • Improve metabolic flexibility

  • Improve insulin sensitivity

  • Reduce blood glucose levels

  • Balance hormones

  • Delay ageing

  • Improve gut microbiota

  • Promote weight loss

  • Reduce inflammation

  • Reduce oxidative stress

  • Promote organ healing

  • Improve energy, mood and cognitive function

  • Reduce hypertension

  • Protect against heart disease and strokes

  • Improve heart rate variability (HRV)

  • Boosting cognitive performance

  • Improving overall health

How to Fast

Lunch, soup, heath, regenerative diet and fasting
Photo credit: The Regeneration Diet (Day 2 Lunch) Michelle McKenzie

Fasting has no standard duration, with a few different types to choose from depending on the outcome you desire.

As listed, these include time-restricted eating, intermittent fasting (different durations), 24hr fasts, 36hr fasts, extended water-only fasts (3-5 days), dry fasts (24hr) and the fasting-mimicking diet (FMD).

Time-restricted eating

This is a great place to start if you are new to fasting, and to be honest, it used to be the normal way of eating until the 1970s.

There is one fast that I recommend to all my clients - time-restricted eating - which should ideally be carried out on a daily basis.

Time-restricted eating is a type of intermittent fast that involves an overnight fast that incorporates a twelve-hour (at least) window every day without food. As you’re sleeping the majority of the time, all you have to do is dodge the snacking that can take place in the evenings.

There are differing opinions on how long the daily duration should be; some experts recommend leaving as long as you can between dinner and breakfast, with some recommending that you miss breakfast altogether and just have lunch and dinner.

Based on the research, I recommend 12 – 14 hours without feeding and having dinner as early in the evening as possible so you can give your digestive system at least a couple of hours to break down your food before you go to bed. For example, if you eat at 7 pm in the evening, then you can happily have breakfast at 9 am, and that will be 14hrs. Daily 14-hour fasts give you a period of low insulin levels which can help prevent the development of insulin resistance. It also allows time for your digestive system to digest and rest. Intermittent fasting is beneficial for everyone and especially if you want to lose weight, increase energy levels and improve brain fog.

24-hour fast

Longer fasts, such as 24hr fasts, involve fasting from dinner to dinner or breakfast to breakfast. Despite being called a 24hr fast, you still have one meal a day, sometimes called a one meal a day (OMAD) fast.

During this time period, autophagy begins.

Autophagy is a cleansing process and the body’s response to a lack of food that triggers a degradation pathway on a cellular level. By digesting its own parts, the cell does two things:

  1. It rids itself of unnecessary proteins that may be damaged or malfunctioning

  2. It recycles amino acid ‘spare parts’ into new cellular components

This process was initially thought to be non-selective but was later shown to be able to target damaged organelles and invading pathogens. This type of fast can be carried out safely once or twice a week.

36-hour fast

A 36-hour fast involves fasting from dinner on day 1, skipping meals the next day - day 2 - and enjoying breakfast on day 3. After 24 - 36hrs of fasting, there are lots of wonderful health benefits taking place.

This is a magical length for seeing changes in your gut health.

The body makes stem cells, and those stem cells will replace old worn-out stem cells. Extending a fast from 24 to 36 hours will invigorate your gut microbes and repair the gut lining.

This length of fast triggers intestinal stem cell regeneration, BDNF protein increases (fertiliser for the brain) that repairs neurons and dendrites (brain fog, memory, depression), there’s a serotonin boost (when BDNF goes up, serotonin goes up), and there is a marked reduction in anti-inflammatory markers (CRP levels) & blood pressure.

The longer the fast, the longer these switches remain on. This period of fasting has been reported to help put Type 2 diabetes into remission when followed for a particular period of time.

Breakfast of berries and herbal tea regenerative diet and fasting
Photo credit: The Regeneration Diet (Day 1 Breakfast) Michelle McKenzie

Fasting-mimicking diet (FMD)

The fasting-mimicking diet is a five-day fast created by Dr Valter Longo.

It is scientifically designed to mimic the effects of water fasts by tricking your body into thinking you are abstaining from food. After conducting clinical trials with water fasts, Longo realised that most individuals (especially those who are sick) found it difficult to adhere to such extreme fasts.

He started experimenting with macronutrient combinations to investigate if there was a way of receiving all the benefits of water fasts by consuming a low-calorie, low-protein, low-carbohydrate diet.

Longo’s research discovered that when limiting protein and calories (25g protein on day 1 and 15 -17g on days 4 – 5; 1100kcal on day 1 and 700 – 800kcal on days 2 – 5), you can enter into a fasting state while still enjoying small amounts of food.

This type of extended fasting is perfect for those intimidated by water-only fasts.

It allows you to experience all the benefits of being in a fasting state for a longer period of time.

This type of prolonged fasting represents the safest and most potent way to reverse many age and diet-related problems by fixing, replacing and rejuvenating cells, systems and organs naturally.

It awakens a highly coordinated response already built into the body by taking advantage of billions of years of evolution to activate a self-

healing program.

Implementing your fast

Various fasts can be used as a tool at different times of the week, for example, daily time-restricted eating set at different times, one 24hr fast per week and a quarterly fasting mimicking style fast.

It is important to understand which fasting works for you personally so you can gain the benefits rather than simply stressing your body out. Women will also benefit from fasting alongside their natural hormone cycles, i.e. when to fast and when to feast with fluctuating oestrogen and progesterone levels.

Fasting is the greatest remedy; it is the physician within us all.

Caution: Fasting periods lasting longer than 24 hours and especially those undertaking longer periods, should be done under supervision, especially if on any medication.


The Regeneration Diet

I caught covid in March 2020, and after the initial infection, I spent the next 11 months dealing with an onslaught of different symptoms from nerve pain, internal tremors, ear infections, rashes, headaches, jaw, muscle and joint pain, brain fog and last but not least, extreme fatigue. It was a rollercoaster ride of physical and mental peaks and troughs.

As a nutritionist, I felt very grateful that I understood what our bodies need to thrive and heal and was happy to experiment on myself the one thing that made a huge difference was fasting. Based on the research by Dr Valter Longo, I designed a five-day fast that I could repeat until I felt better, and it worked (alongside supplements, cranial osteopathy, qigong and acupuncture). As mentioned above, when we fast, our clever bodies break down the unhealthy organelles and leave the healthy organelles, essentially ‘cleaning’ up the cell and the mitochondria. This is why this fast length is so powerful and can play a role in both the prevention and reversal of the disease.

  • Switch all cells to a protected anti-ageing mode

  • Prompt autophagy

  • Reduce inflammation

  • Stimulate stem cell regeneration which can influence healing throughout the whole body

My five-day diet, now called The Regeneration Diet, promotes regenerative changes throughout the entire body by reducing inflammation and targeting damaged cells which in turn increases energy levels which is exactly what my body needed to do.

107 views0 comments

Related Posts

See All


bottom of page