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Intermittent Fasting – The Low Down

The latest buzz around people’s eating routines and one of the most popular health and fitness trends today is ‘intermittent fasting’ (IF). With this, though, basic questions about what IF is and whether it works also come up.

“Why is it that just a few years ago we were told to eat regular meals and snacks for health and weight optimization and now we are meant to skip BREAKFAST and fast”, is just one of the questions I often get.

Let’s unpack the basics and ins and outs of IF and find out what the science says.

What is Intermittent Fasting?

IF describes an eating pattern that cycles between periods of fasting and non-fasting (eating). It doesn’t necessarily dictate what and how much you should be eating, but rather when you should be eating.

IF is promoted for changes in body compositions (fat and weight loss), longevity and cognitive ability, improved health markers as well as improved blood sugar and cholesterol levels.


Different Fasting Methods

There are different types of fasting methods. Some of the most popular IF eating regimes are:

  • The 16:8 Method. The 16:8 fasting method, also known as the Leangains Fasting Protocol, is the most popular type of Time Restricted Feeding routines. In this method, you fast for 16 consecutive hours and eat during the remaining 8 hours. This means if you stop eating dinner at 8pm, you fast until 12pm the following day. The only thing you can have during your fasted state is water, plain herbal or black tea as well as black coffee (no milk nor sugar).


  • Alternate-day fasting. Also known as the eat-stop-eat fasting mechanism, includes complete fasting for 24-hour periods on 1 to 2 days per week; while the other 5 days incorporate normal eating routines. This method is usually done by having a very early dinner or skipping it all together, followed by a 24 hour fast until dinner the following day.


  • Modified Fasting. This form of IF also known as 5:2 involves a ‘fast day’ where individuals eat 25% of their usual caloric intake for the day for two non-consecutive days a week, while the other five days a week involve normal dietary intake.


Physiology of Intermittent Fasting

Glucose and fat are used by the body as the main source of energy. Glucose is usually used first as it’s the most accessible source of fuel and when we eat glucose is readily available. However, when glucose is not available to use as fuel, such as in a fasted state, the body switches to using fat as its main fuel source, thus resulting in ‘fat burning’.

Various hormonal changes also take place during a fasted state. One of most common hormonal changes that takes place during fasting is a drop in insulin. This allows for fat stores to be more accessible. Another hormonal change that takes place is an increase in human growth hormone. This hormone stimulates growth and cell regeneration.

Research on IF and its benefits is varied for numerous reasons. Many of the compared studies either use different fasting methods; aren’t performed for long enough to see significant results or the research is done on mice, not humans. So, while there is lots of theory around IF, studies are still being done to produce conclusive evidence. That said, the rise in research showing the benefits of IF for some individuals is becoming more apparent and, as always, it should be done under the guide of a professional dietitian.

Health Benefits of Intermittent Fasting

Weight Loss and Intermittent Fasting

Weight loss is by far the most studied effect of IF. It seems logical that one would lose weight through IF as controlling when you eat and skipping meals naturally results in calorie restriction. According to the research, different fasting mechanisms have varying effects regarding weight loss, with restricted fasting methods showing a decrease in daily caloric intake and body weight, and modified fasting showing a significant weight loss of 6.5%.  .

Some studies show that these fasting methods aren’t necessarily more effective than normal calorie restrictive diets. However, research shows that it can result in less muscle loss in time restricted fasting methods.


Aside from the research of IF and weight loss, IF is in the spotlight when it comes to the potentially powerful benefits it may have on our health.

Let’s take a closer look at some of the studied health benefits below.

Insulin Resistance and Diabetes

Insulin levels increase when we eat and decrease when we fast. Significant reductions of insulin levels occur during IF, which in turn result in weight loss and a reduced rate of diabetes. A study showed promising success of reducing the risk for type 2 diabetes in the overweight population but it is important to note that more studies are needed to confirm the effects of IF on diabetes.

Patients who are diabetic should not IF, especially not without the help of a health professional.

Inflammation and Oxidative Stress

Inflammation and oxidative stress are the underlying causes of many chronic diseases such as diabetes, cardiovascular disease, immune diseases, obesity and cancers. Through IF, a mild stress response is activated in our cells, to which our cells respond by upregulating their anti-oxidant and anti-inflammatory pathways to counteract and ‘reduce’ the stress. Especially prolonged phases of fasting can reduce inflammation.

Cardiac Health: Blood Pressure, Cholesterol

IF may promote cardiac health. This is more prevalent in alternate-day fasting which indicated a reduction in LDL cholesterol (the unhealthy cholesterol) as well as blood pressure. Recent human studies, also showed that IF improved cardiac health through the reduction of inflammation and oxidative stress that occurs in the body.

Increased Longevity and Aging

While most of the studies linking IF and longevity have been done in mice, with lifespans being 36% – 83% longer once fasted, there is a valid promise that more human studies will have the same results. One of the theories is that IF promotes what is known at ‘autophagy’ – ‘self-eating’, which can be viewed as the body’s way of cleaning house and clearing all the damaged and potentially harmful cells from the body, resulting in longevity and improved health.

Exercise and Intermittent Fasting

One can exercise during a fasted state and it has shown to have positive results, but this all depends on what your goal is, how long you are fasting for and whether you train better in a fasted or fed state. A combination of exercise and alternate day fasting has shown to favourably change cholesterol as well as body weight in obese patients. This all depends on what type of fast you are doing and whether you perform better on an empty stomach or after fuelling.

Take Home Message

IF has certainly gotten everyone’s attention. On the plus side, some research has shown that IF can be a great tool when it comes to fat and weight loss. There is some further evidence that it can improve cardiac, inflammatory and oxidative stress markers; reduce risk for insulin resistance; improve concentration and cognitive function; and increase longevity. Advocates of IF claim that even though it shows the same benefits as seen with calorie restrictive diets, it is easier to follow and has increased compliance making it a more sustainable approach to healthy daily caloric reduction as well as reducing your appetite and snacking.

But, is it for everyone? Much of the research has been done on animals or small subject groups meaning substantial further research in humans is needed. It is also important to remember that there is never a ‘one-size-fits-all’ approach when it comes to weight loss or healthy eating – even within IF itself there are different methods of fasting.

People with advanced diabetes on insulin, suffering from chronic diseases, on medication, pregnant or breastfeeding women as well as those with a history of anorexia, bulimia or any form of disordered eating should not attempt intermittent fasting.

It is not an approach for everyone, but it can be a dietary strategy to consider. If IF sounds like something you want to try, talk to a dietitian and see if really is right for you.

Nourish yourself to the sunrise.

Written with love ,
Sunrise by HM

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