🥙 Nutrition

Intermittent Fasting for Digestive Health

Updated on Mar 11, 2024

Whilst most diets focus on controlling what you eat, intermittent fasting controls when you eat, giving you a very specific window in which to take in your daily calories. Among other things, intermittent fasting can have very positive effects on your digestive system.

Fasting periods can change depending on goals, protocols, and individuals. For instance, some people will follow a 5:2 pattern, in which they eat normally five days per week, and greatly restrict their calories (down to 500 or so) for the other two. Others will maintain a daily fast of 16-20 hours, meaning that they eat everything in a 4-8 hour window.

This is easier than it may sound. Most people need to sleep around 8 hours per night, and hopefully manage to do so. Assuming you take in no calories when you eat (and most of us don’t!) this means that you’re already fasting for 8 hours. If you then don’t eat until 11am, and have your final meal before 7pm, you’ll be fitting your food into an 8 hour window with relative ease.

Types of fast

I’ve mentioned a couple already, but just for your reference, let’s look at the most popular protocols for fasting that people typically use.

  • The 5:2 diet: as mentioned above, this involves two low calorie days per week. This will usually be a quarter of your usual amount.
  • The alternating diet: similar to the 5:2 diet, this gives you periods of fasting on different days. Every other day, you eat a quarter of your usual caloric need.
  • The 16/8 split: again, I mentioned this above. It’s one that I’ve used myself to great effect. Pick a start and an end time 8 hours apart (I often do 12-8pm.) Eat all of your calories in this time frame, and none outside of it, giving yourself 16 hours out of every 24 in which to fast.
  • The 22/2 split: this is an extreme version of the 16/8. You simply eat everything within a two-hour time slot. Typically, this means eating one large meal per day.

It’s not recommended for anybody to try any extreme version of fasting without first seeking medical advice, especially if they suffer with any pre-existing health concerns.

Intermittent fasting: the theory

Why do people do this; what are the health benefits of intermittent fasting? There are a few. The most important thing you need to understand is that the human body goes through a few subtle yet important changes during extended periods of fasting. Insulin levels in the blood drop significantly, as do stomach acid levels. In addition, human growth hormone (HGH) levels rise and cellular repair processes increase in many instances.

Another important factor behind people taking on fasting periods is the weight loss element.

A couple of mechanisms aid you in weight loss here. Primarily, if you limit the amount of time in which you’re eating, it’s almost inevitable that you take in fewer total calories. Grazing all day long, for 14-18 hours or so, allows you to eat a lot of unnoticed, unnecessary macronutrients.

In addition, stabilised, decreased insulin levels will stop you being so hungry and will stop you from having energy surges and crashes. Boosted HGH levels will allow you to lose fat whilst maintaining lean muscle mass. Overall, your metabolic rate can be increased by anything from 3-14% on an intermittent fasting protocol.

This also has great carry over for gut and digestive health, which I want to focus on below.

Digestive benefits of intermittent fasting

The main benefit comes with basically giving your digestive system a break. If you have any kind of reflux or stomach bile/acid issues, this should be of great benefit as you will have more time for your stomach’s acid levels to return to normal. If you ever have any symptoms of digestive stress (IBS etc.) then you will be decreasing the amount of time you have to deal with it.

This rest will also reduce postprandial endotoxemia, a metabolic risk factor, which has been found to increase the risk of obesity and insulin resistance. The composition of your friendly gut flora and bacteria can also be improved by fasting periods.

Aside from this, our circadian rhythm (our internal body clock) plays a part. Fasting benefits our gut bacteria because they also have their own circadian rhythm. Many types of gut flora oscillate activity levels through the day, and many even fluctuate in abundance.

One example is the gut microbe Enterobacter aerogenes. This bacterium is melatonin sensitive (melatonin being the ‘sleep’ hormone.) Enterobacter aerogenes’ main role is in sugar fermentation and gas production. Circadian rhythm disruption- through, for example, protracted or late-night eating- can cause disruption to the Enterobacter aerogenes which will negatively impact metabolic health.

This is a young science: researchers are only just starting to understand how intermittent fasting may aid gut health and flora. They are only just starting the process of theorising as to the health benefits of fasting for regular, extended intervals.

However, from what we can tell so far, the benefits are there. From the first-hand testimonial to the most recent in breakthrough research, the consensus seems to be growing that intermittent fasting has a positive overall benefit on our digestive health.

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James Dixon
James Dixon
James Dixon is a fully qualified personal trainer, with a decade’s worth of experience under his belt. Throughout his career, he has helped hundreds of people to meet their dietary and fitness goals, writing exercise and nutrition plans to suit any and every requirement.


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