Intermittent Fasting

17 February 2021
By Brett Durney

When you’re on a quest to be the fittest, healthiest version of you, working out is only part of the equation. If you’re training hard, you need to optimise your recovery and make sure that you are fuelling your body properly – this means getting clued up on nutrition.

As with so many things in health and fitness, there are a wide variety of different approaches – it’s a case of experimenting with what works best for you, your lifestyle and your body. One concept that has recently grown rapidly in popularity is “intermittent fasting” (IF). This involves cycles of fasting and eating which can be adapted depending on your age, activity level and lifestyle.

So first, let’s take a look at the benefits of fasting…

Weight loss

Intermittent fasting is often used as a tool for weight loss, and with good reason. Following a conventional eating pattern, we fast between dinner and breakfast – hence the name for our first meal of the day, where we “break” our “fast”. Lengthening the time you spend fasting and restricting your “feeding window” automatically makes it easier to reduce your caloric intake, which is one the key things to focus on when it comes to driving weight loss (the other, of course, being increased physical activity).

However, this will only work as long as you don’t overcompensate for your fast by eating excessively during your allocated eating hours! If your calories are the same as what you would usually eat, or if you find yourself unable to resist overeating calorie-dense foods when you are “allowed” to eat, then maybe intermittent fasting isn’t the best approach for you, especially if weight loss is your goal.

Inflammation reduction

Inflammatory responses in the body are a vital part of the immune system, helping to heal injuries, defend against viruses and bacteria and repair damaged tissue. However, it also has the potential to do a great deal of harm when the body mistakenly starts to attack its own tissues. Low-level, chronic inflammation has been linked to a long list of chronic health issues, from heart disease, autoimmune conditions, arthritis, diabetes, cancer, digestive problems, anxiety, depression, brain fog, and hormonal problems.

A number of studies have suggested that fasting can reduce inflammation, by triggering anti-inflammatory responses such as:

  • Positive changes in the composition of gut microbiota
  • Reduction of insulin resistance
  • Increased immune response in cells
  • Increased production of β-hydroxybutrate, a compound that blocks part of the immune system responsible for inflammatory disorders like diabetes, Alzheimer’s disease or rheumatoid arthritis
  • Significant reduction in the presence of inflammatory markers such as cytokines, C-reactive protein

Enhance your gut health

When we refer to  the “gut”, we mean the digestive tract that your food passes through, which encompasses many different parts of the body, including the oesophagus, stomach, small and large intestines and the colon. Within the gut, an army of microbes (vast numbers of microorganisms and diverse bacterial communities) work with our cells to keep us alive and healthy. Around 80% of our immune system lives within the gut microbiome, impacting almost every aspect of how we feel. As well as supporting our immune system, good bacteria in the gut can soothe inflammation, promote absorption of nutrients and minerals, stabilise glucose levels, balance hormones, aid digestion and fight against bad bacteria and pathogens that contribute to disease. There is even evidence that the bacteria in our gut plays a key role in our mental and emotional wellbeing.

Constantly eating, going from breakfast to snack to lunch to snack to dinner, means that not only are we out of touch with our body’s hunger signals, we are also constantly digesting food. We have something in our stomachs all the time. Humans are the only animal with constant access to food – and this is a relatively recent change in our dietary habits. Our ancestors had to forage for their own food (no 24-hour supermarkets back in caveman days!), so they did not follow a clockwork regime of 3 meals per day with a steady supply of snacks to graze on in between. Evolutionarily-speaking, our bodies are actually designed to cope for fairly prolonged periods without food.

Fasting gives your overworked gut a break from constantly processing our food and allows it to devote time to the many other roles it has to play. What’s more, when you fast, your blood sugar levels and insulin concentrations both fall, which may help to reduce the risk of developing Type 2 diabetes by reducing resistance to insulin.

Boost brain health

Intermittent fasting causes an increase in levels of a brain hormone called BDNF, which promotes the growth of new nerve cells and increases the resistance of neurons in the brain to dysfunction and degeneration. Some studies have shown that changes in neurobiological mechanisms triggered by intermittent fasting can help to prevent the onset of conditions like Alzheimer’s.

Ongoing research shows that adjusting meal size and frequency may affect human health more deeply than we realised, so in the future IF may well be used as an approach for disease prevention and treatment.

Learn to recognise your body’s hunger signals

If you think about it, we very rarely experience “real” hunger. We eat breakfast because our parents drilled into us that it’s “the most important meal of the day”, we automatically reach for our lunch when it hits 12.30 because this has always been the designated lunch break granted to us by our teachers, and, later, our bosses. Eating on autopilot, we rarely stop to ask ourselves whether or not we are actually hungry. Extending your fast is a way of learning what hunger actually feels like, so that you are better able to distinguish between eating out of habit and eating in response to your body actually sending you signals that it needs fuel.

Becoming more in tune with your body is really empowering and especially important when you’re trying to learn what works best for you as part of a commitment to improving your health and fitness.

Different types of intermittent fasting

There are many different types of intermittent fasting – as touched on earlier, it’s all about finding the approach that works best for your lifestyle and your body. It can be worth experimenting with different approaches and seeing how you feel.

Firstly, we have the 16:8 method. In this kind of IF, you limit yourself to an 8-hour feeding window, fasting for the other 16 hours of the day. The easiest and most popular way that people achieve this is to skip breakfast, then eat from 12PM – 8PM. This is ideal if you work out in the afternoon, as you can eat some healthy carbohydrates for lunch, with plenty of calories left for a post-workout protein shake in the afternoon before dinner. It’s relatively easy to stick to, as you only need to skip one meal, so it’s a good place to start if you’re new to fasting

A second approach is the 24-hour fast. This one is fairly self-explanatory and involves fasting for an entire day at a time. People following this method usually do one to two fasts per week, by not eating from one dinner until the next. This is more challenging than the 16:8 approach and will likely be pretty difficult to adhere to if you’re new to fasting.

The 5:2 method is a third approach and in terms of difficulty sits somewhere between the 16:8 and 24-hour methods. Popularised by celebrities in recent years, this type of fasting requires you to eat normally 5 days of the week, then restrict your intake to 500-600 calories for 2 non-consecutive days.

With all these approaches, the key is to eat normally when not fasting. If you overcompensate for the fast by eating a ton more calories than you normally would, then a calorie deficit is not achieved, which is usually one of the key objectives achieved by trying out IF.

Working out and intermittent fasting

It goes without saying that if you choose to experiment with intermittent fasting, you need to do so sensibly and figure out when it makes sense for you to eat! You need to have enough fuel to work out, and you should be able to nourish your body with carbohydrates and protein after an intense session at the gym. So, opting to fast from dinner to lunch the next day if you’re planning a workout at 9am may not be the best strategy – not only will you be running on empty, you also won’t be able to refuel immediately. Not ideal.

Top tips

  • Don’t overeat when in your feeding window – this defeats the point if your goal is weight loss
  • You can’t intermittent fast yourself out of a bad diet – you still need to focus on building a healthy diet, that includes plenty of veggies, fruit, good sources of protein and wholesome carbs
  • Make sure that you stay hydrated during your fast. As well as water, you can have herbal tea and coffee without milk or sweetener during your fasting hours
  • Many people successfully use intermittent fasting as a tool for weight loss, as it helps them to reduce the number of calories they consume. However, as with any diet that puts you in a calorie deficit, it’s key to ensure that your protein intake is adequate and that you perform regular resistance training. This will help to ensure that the weight you lose comes from fat, not muscle, and therefore improve body composition
  • Ease into it – it won’t be easy at first to go without food when you’re used to eating! Set yourself achievable, realistic goals. Try extending your fast by an hour at a time, taking a couple of days to adjust before extending again when you feel ready to


Venter JC, Adams MD, Myers EW, et al. : The sequence of the human genome. Science2001;291:1304–1351

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