How can intermittent fasting improve digestion and gut health?

- and how to incorporate the 12:12 protocol into your daily routine

I've had such positive experiences with timing my food intake that I wanted to share more about the slightly controversial topic of intermittent fasting. Intermittent fasting is often discussed in relation to weight loss, but my interest lies purely in how it supports gut health, improves our gut microbiome and can ease digestive symptoms.

What is intermittent fasting (IF)?

Intermittent fasting (also called time-restricted eating) refers to a method where you eat during a certain time of the day and abstain from food for the rest of the 24-hour period. The most well-known method of intermittent fasting is the 16:8 method, where you eat all your meals during the 8-hour eating window and fast (meaning, don't consume any calories) for the remaining 16 hours. Another common method is 5:2, where you eat normally for 5 days and eat around 500 kcal/day or nothing the remaining 2 days.

I personally follow the 12:12 protocol. As the name suggests, this method divides the day into two - 12 hours for eating and 12 hours for fasting. When possible, I try to extend the fasting part to 13-14 hours but sometimes life gets in the way, and I believe it's best to avoid being too strict with it.

There are many methods, and basically any eating style where your body periodically ends up in a fasted state can be called intermittent fasting. And the interesting thing is that from a digestion perspective, already shorter fasts, such as the 12:12 protocol, can be beneficial. Let’s have a look!

Fed state, post-absorptive state, and fasted state - what is the difference?

When talking about intermittent fasting, we often simplify it and talk about "eating" vs "fasting", but it's essential to recognize that the body does not immediately enter a fasting state the moment we stop eating.

Our body is in the so-called fed state from the moment we start eating a meal until 3-5 hours after finishing the meal. During this phase, insulin levels rise, causing the body to store excess energy from food.

After that, our body is in a post-absorptive state 5-8 hours after finishing the meal. This means that our body isn’t reaching the fasted state until 8-12 hours after the last bite. As the body depletes the stored glycogen for energy and insulin levels drop, it switches to a fasted state. In the fasted state, the body switches from burning blood glucose to burning stored fat for energy.

Keep in mind, that the timing it takes to transition from a fed to a fasted state can vary from person to person, based on factors such as the last meal's content and individual metabolic rate.

Back in the day we ate food when we had it, and we naturally fasted when food was not available. Now we have constant access to food and different snacks and have been told to eat small meals throughout the day to avoid getting hungry. This means that most of us almost never end up in a fasted state, and during the day we won’t even get to the post-absorptive state, since many people eat something every 3 hours.

When practicing intermittent fasting, the aim is to extend the fasted state as long as possible to maximize the health benefits such as improved cognitive health, longevity, reduction of inflammation in the body, weight loss, improved cellular repair, amongst many others.

Intermittent fasting for digestion and gut health

Although we ideally want to achieve all the health benefits of a longer IF protocol mentioned above, already 12 hours of fasting is beneficial for digestion and way easier to implement. The 12:12 protocol can also be an easy way to start intermittent fasting, and you can slowly increase the fasting period up to 16 hours.

Fasting essentially offers a 'digestive break,' allowing the gut a much-needed period of rest from the constant processing of food. This resting phase not only makes your digestive system more efficient when you do eat, but it also significantly contributes to better gut health.

Here’s some examples of how intermittent fasting can support the gut health:

• Balances the pH levels in the stomach – Especially beneficial if you’re suffering from acid reflux, as fasting can temporarily lower stomach acid production.
  

• Helps to relieve IBS (irritable bowel syndrome) symptoms and other digestive discomfort – gives the gut a break and more time to recover.
  

• Diversifies the gut microbiome – fasting regularly can reduce the population of harmful bacteria while allowing beneficial bacteria to flourish.
  

• Can repair the intestinal lining (gut barrier) – a healthy gut lining prevents harmful substances from leaking into the bloodstream, which again reduces gut-related inflammation and autoimmune reactions.
  

• Encourages structured and mindful eating – intermittent fasting can help make better food choices and reduce late-night snacking.
  

• Balancing the hormones related to digestion and hunger – helps to control appetite, reduce overeating, and manage blood sugar levels.

Intermittent fasting has been linked to the improvement of gut microbiota, the community of bacteria living in the intestines that play crucial roles in our health. A healthy microbiota supports digestion, and intermittent fasting has been found to modulate this gut microbiota diversity positively. Fasting allows the bacteria to break down food more efficiently, leading to better nutrient absorption and reducing the instances of bloating and discomfort.

How to incorporate 12:12 fasting into your routine

Circadian rhythm and how to time your fast

It is not totally irrelevant when do you fast during the 24-hour period. You should time your fast with your body’s natural circadian rhythms, which are natural 24-hour internal biological cycles. They respond mostly to light/dark and regulate various physiological and behavioral processes, like the sleep-wake cycle, hormone production, cognitive function, digestive- and metabolic function, to name a few.

Research shows that eating during daylight and refraining from eating after sundown is optimal for our health and can improve digestive symptoms such as bloating, diarrhea, and constipation. We can assume that we wouldn't anyway eat during the night or while sleeping, and therefore the easiest (and as mentioned, the healthiest) way to time your intermittent fasting is around your sleep cycle.

This can easily be done by having your last meal of the day earlier and eating your first meal of the day later. Even if not practicing intermittent fasting, I recommend finishing your last meal at least 2-3 hours before going to bed. If your body is still fully digesting food when you’re heading to bed, it will affect your sleep quality.

Assuming you sleep for 8 hours, not eating for 2-3 hours before bed will already create a fasting period of 10-11 hours without really restricting your life. Some research show that the optimal way is to refrain from eating for at least 1 hour after waking up. Depending on your schedule, you could then stop eating at 7 PM and have your breakfast at 7 AM, or alternatively 8 PM/8 AM.

What can I eat or drink during a fast?

Keep in mind that drinking water during your fast is not only allowed but highly encouraged. It is important to stay hydrated. You may also drink tea and coffee, but only if they don’t have any sugar or added calories. Adding a splash of milk to your coffee should not interfere with the fast. However, from a health perspective, I would generally recommend having your coffee after or together with your first meal of the day, as drinking coffee on an empty stomach can irritate the gut.

What should I eat during the eating period?

As important as it is to give our digestive system a break from food, it is at least as important to pay attention to what we eat. From a gut health perspective, we should limit the use of ultra-processed foods and artificial sweeteners. These alter our gut microbiome and don’t provide ideal nutrients to our body (more on this on another blog post).

To support a healthy gut microbiome, it's best to focus on whole foods like fruits, vegetables, whole grains, eggs, fish, legumes, and fermented foods like natural yogurt or kimchi. If you’re not aiming to lose weight, you can consume the same amount of food as you usually would. Intermittent fasting, by its principle, doesn’t limit what or how much you eat, only when you eat.

It is interesting though, that even when consuming the same amount of food and calories, you might burn more fat. This is because during the fasted state, your body can access the fat storage in your body and use that as energy. However, in the 12:12 protocol the fasted state is relatively short, so I do recommend the 16:8 protocol if your focus is on weight loss.

The challenges of fasting

The benefit of a 12-hour fast vs. longer fasts is that it is easier to implement, but you might still experience some challenges:

• Altered mood – being irritated because of hunger.

• Hard to focus – if you are hungry, it can be hard to focus on anything else.

• Muscular weakness and dizziness

The good news is that these symptoms usually disappear after your body has gotten used to the new eating pattern. This might take up to 3 weeks, but most people find it gets easier already earlier.

How soon do I feel better when fasting?

It is very individual how fast and how big improvements you feel after implementing IF, but if you are used to eating often and late at night, you might notice improvements already after a few days (despite the side-effects mentioned above) on this 12:12 fasting protocol. You might feel less bloated, have more regular bowel movements, be less constipated, be less reactive to triggering foods and experience less heartburn, to name a few.

In conclusion, incorporating intermittent fasting into your lifestyle, specifically a balanced 12:12 protocol, can significantly enhance your digestive health and overall well-being. It is simple to follow, and a shift towards this mindful eating approach has the potential to create positive effects on your health, making it a nutritional strategy worth considering.

What's next?

Intermittent fasting is a great starting point, but if you feel you need more support, I’m here to help you build healthy, sustainable habits that support your digestion and give you more energy, emotional balance, and less digestive discomfort. In my Two Thirds Nutrition signature program, we'll meet online bi-weekly and you'll get a personalized health plan including weekly meal plans, a lifestyle assessment, and a list of supportive supplements. We will work together for 3 months to finally tackle those digestive issues for good.

Check the TTN signature program for more information or book a free 15min discovery call.

*Disclaimer: While intermittent fasting is safe for most people, I encourage you to talk to a medical professional to make sure that intermittent fasting is suitable for you, especially if you have a medical condition or a history of disordered eating.