Timing when you eat: Why periodic fasting can have a such a huge impact on your health.

You’ve probably heard of people doing ‘intermittent fasting’.

Some follow the popular 5:2 diet, while others might only eat within a specific window of the day.

Regardless of the method, essentially it all comes down to timing when you eat and monitoring calorie intake within those times.

What is intermittent fasting?

“Intermittent fasting is a general term used to describe a variety of approaches that change the normal timing of eating throughout a day, with short-term fasts used to improve overall health,” Dietitian Robbie Clark told Mamamia.

“In other words, the one consistent theme of intermittent fasting is that individuals periodically fast for a longer duration than the typical overnight fast that occurs while you sleep.”

The overall health benefits Clark refers to go way beyond weight loss (more on those later) but of course fat loss can be a result for those who are overweight. First, let’s take a little science lesson in what happens when we eat.

“When we eat, we ingest more food energy than our body can immediately use. As a result, this energy is stored away for later use,” Clark said.

“Enter the hormone, insulin. Insulin is the key hormone involved in the storage of food energy. To put it simply, insulin rises when we eat, helping to store the excess energy, known as glycogen, in the liver. There is, however, limited storage space, and once that is reached, the liver starts to turn the excess glucose into fat.”


Through fasting the process is essentially reversed, whereby the body calls on the excess energy stored as fat to use as the energy it needs to function.

“When we fast, insulin levels fall, signalling the body to start burning stored energy, since no mfore is coming through food. Blood glucose also falls, so the body must now pull glucose out of storage to burn for energy,” Clark said.

Intermittent fasting, also referred to as periodic fasting, works on the stop-start premise so as not to slow the metabolism down in a detrimental way, which can occur with long, extended periods of not eating.

How is intermittent fasting done?

There are a few different approaches to intermittent fasting. Below, Clark outlines some of different types:

The 5:2 Diet

This is one of the most popular intermittent fasting plans. The diet allows you to follow a ‘normal’ healthy pattern of eating for five days followed by two ‘fasting’ days. On fasting days, energy intake is restricted to around 500 calories for women and 600 calories for men, per day.

Fasting days can be consecutive or split over the week. The daily calorie allowance can be eaten over various combinations of one, two, or three meals plus snacks, depending on personal and practical preferences.

There are also variations of the 5:2 Diet, including 6:1 (restricting only one day per week), 4:3 (restricting three days per week) or ADF (alternate day fasting).


16/8 Fasting

This method recommends you fast for 16 hours a day and limit your eating to an eight-hour window. Most often, this simply involves skipping breakfast and eat between the hours of 12-8pm.


With this method, you pick one or two days out of the week and fast for 24 hours, eating nothing from dinner one day until dinner the next day. On the other days, you should aim to eat normally.

Lots of fluid is encouraged during these fasts.

LISTEN: Radio Presenter Robin Bailey details her relationship with food, for better and worse. Post continues after audio.

What are the benefits of intermittent fasting?

“Fasting’s most obvious benefit is fat loss. However, research has shown that there are numerous benefits beyond this,” Clark said.

And there’s plenty of research. Periodic fasting has been proven to reduce oxidative stress and inflammation in the body and a Harvard study shows how intermittent fasting may actually increase lifespan.

Other studies have looked at the improved brain and memory function, while anecdotally many fasters report an overall feeling of sharpness and lifted mood.

“Fasting helps normalise insulin sensitivity – lowering insulin production means you decrease your risk of insulin resistance, which can be a precursor of type 2 diabetes,” Clark said.

It also aids in improved immune function – your body kick-starts stem cells into producing new white blood cells, which fight off infection.”


 What are the downfalls of intermittent fasting?

As with any approach to health and wellness, it’s certainly not one size fits all.

“I would strongly recommend that people work with a qualified healthcare professional or dietitian who understands the risks and benefits and can help determine if it’s right for you.”


“For example, intermittent fasting should always be avoided during pregnancy and breastfeeding, and should generally be avoided during times of increased stress. It is also not recommended if you are a child or teenager as it may interfere with growth and development. People with uncontrolled diabetes should also proceed with caution,” Clark said.

Mark Robinson, Accredited Practising Dietitian, also warns against the risk of calling on the methods of intermittent fasting too often.

“The trick is to not make intermittent fasting the new ‘norm’ for the body because then it can go into a storage mode and slow down metabolism. When this happens, the body starts holding onto our calories from our meals because it does not know when the next intake will be and somewhat prepares for a fast, which is unhealthy.”

Clark also says to be wary of becoming over reliant on caffeine, as coffee is allowed during fast periods in a lot of the formulated food plans. This has the potential to lead to poor sleep and even anxiety.

“Other health risks that are generally associated with diets that are too low in calories, include risk of nutritional deficiencies, electrolyte abnormalities, and potentially more serious risks if extreme diets are undertaken without appropriate supervision.”

As with any adjustment to your diet, make sure you get the all clear from your doctor first.

Have you tried intermittent fasting? Tell us your experience in the comments.


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