You may have heard of various forms of intermittent fasting - the 5:2 diet, the 16 hour window diet etc. These are all under the bracket of intermittent fasting, a time controlled eating pattern.
Unlike a typical ‘diet’, intermittent fasting does not give guidance on what you should be consuming, only when you should be consuming it. It is fundamentally based on the concept that historically humans do not ‘graze eat’ i.e. eating continuously throughout the day and evening; and this can in fact be detrimental to your digestive system.
Historically, humans were hunter gatherers who would go through long periods of famine often during the winter when there were few crops or when there were no animals to kill for sustenance. After a prolonged period of famine, they would enter a feasting period in which they would consume a large meal shared with their tribe. This cycle would then repeat itself.
When you compare this with how humans eat today it could not be more different. We live in a fast food culture: calorie dense food is highly accessible, cheap and palatable. It is common for most to eat upon rising and continue eating every couple of hours until sleep. This eating pattern can cause overeating, due to the extended eating window which can lead to an increased appetite and food cravings. This can then lead to weight gain and obesity.
Alongside the increased risk of obesity, eating continuously throughout the day can wreak havoc with your digestive system. It can take anywhere between six to eight hours for your body to properly digest the food you have consumed. So think about it this way - if you are snacking until midnight and then wake up at 8am and eat breakfast, it is likely that the food you ate the night before has not even been properly digested yet. In extreme cases, this can cause liver toxicity, irritable bowel syndrome (IBS), bloating, inflammation and other undesirable health issues.
So what happens to your body when you fast?
Fasting has been shown to improve biomarkers of disease, reduce oxidative stress, preserve learning and memory functioning, increase muscle mass and reduce body fat - according to recent research undertaken by the US National Institute of Health. This of course depends on a plethora of variables aligning, for example if you are eating large quantities of junk food more so than usual, you will not experience these benefits. However, if you are eating a healthy balanced diet, get sufficient exercise and commit to the time frames of the fasting and eating windows - you will start to notice some of the amazing benefits of intermittent fasting.
The most common form of intermittent fasting is the 16:8 fast, which involves fasting for 16 hours typically during the night time until around midday and then eating until the evening. Essentially you’re cutting out breakfast. This has been shown to suppress the appetite and decrease stomach capacity, which causes feelings of satiety to occur sooner into eating thus resulting in a smaller food intake. So for individuals that are trying to lose weight, fasting can be a great tool.
There are several theories about why fasting provides physiological benefits, one hypothesis being that cells are under a moderate level of stress during a fasting period. This results in cells being forced to adapt by improving their ability to manage stress and resist disease. Studies undertaken by the US Institute of Health have shown a similar physiological response during intense exercise, when the cardiovascular system is under a similar level of stress. The body responds by effective adaptation, similarly to what occurs during intermittent fasting.
If you want to try it, start by only eating for 10-11 hours per day which should be pretty easy for most people, then slowly decrease the eating window. You’ll notice a decreased appetite and feelings of bloating and commonly some weight loss. Give it a try!