Intermittent fasting 16:8 and more: studies, experience & muscle building

Introduction

More and more people practise intermittent fasting regularly to stay healthy, fit and focused in everyday life. Studies on intermittent fasting, whether 16:8, 20:4 or 5:2, have shown positive effects on our bodies and minds. Both athletes and recreational exercisers can benefit from practising intermittent fasting over the long term, particularly for endurance sports and for building muscle without unwanted weight gain.

This article gives you a detailed overview of the main topics related to intermittent fasting.

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Contents

1. What is intermittent fasting?
2. Which intermittent fasting method is best?
   1. Intermittent fasting 16:8
   2. 18/6, 20/4 and 14/10 intermittent fasting methods
   3. 5:2 intermittent fasting
3. Is intermittent fasting healthy?
   1. Studies on the health effects of 16:8 intermittent fasting
4. Intermittent fasting for sport and muscle building
   1. High-intensity training (HIT)
   2. Endurance sport
   3. Strength training, muscle building and intermittent fasting
5. Conclusion

1. What is intermittent fasting?

Intermittent fasting is an eating plan that focuses mainly on when you eat rather than what you eat. The day or week is divided into periods when you eat and periods when you fast.

The aim of intermittent fasting is to establish a routine in your eating plan in which your body uses up excess sugars and fats before receiving new nutrients. According to studies, this has numerous health benefits, including weight management and even the prevention and curing of diseases.

According to Mark Mattson, author and professor of neuroscience, these benefits stem from the fact that our bodies are actually designed to cope with long periods without food, as they did in hunter-gatherer times, while still performing at their best in sport despite intermittent fasting.

Nowadays, however, we spend much more time sitting and lying down instead of walking around, jumping, running or even climbing. We also eat more at each meal and more often. This increases the risk of developing diabetes, obesity and other illnesses.

2. Which intermittent fasting method is best?

Just as the circumstances that once made intermittent fasting unavoidable varied, there are many different methods today. You can find out which method suits you best only by trying it, but we hope the following overview, along with the studies and experiences discussed below, will give you some insight.

2.1. 16:8 intermittent fasting

The 16:8 intermittent fasting method falls between the 18:6 and 14:8 versions and is undoubtedly the most popular.

For example, you can start by setting aside an eight-hour window each day in which to eat, followed by 16 hours when you do not eat.

For example, your eating window might be from 10:00 to 18:00, followed by a fasting period from 18:00 to 10:00.

That does not mean, of course, that you should eat constantly during your eating window. Intermittent fasting, whether 16:8, 18:6 or another pattern, is also about understanding your body’s signals better and staying more active throughout the day by eating smaller meals that satisfy you without leaving you completely stuffed.

Make digestion easier for your stomach! You can do this by watching how much you eat and, of course, by considering what you eat.

After your first meal, you may feel hungry again after 3 to 4 hours and have something small to eat. The point is not to snack constantly, but to eat small, easily digestible meals and wait for your stomach’s signal that it is really empty.

In the evening, it is important to have digested as much as possible before going to bed. Otherwise, you may have an extreme blood sugar shock in the middle of the night, and your body will not know what to do with all that energy.

2.2. 18:6, 20:4 and 14:10 intermittent fasting methods

Besides the 16:8 intermittent fasting method, there are many variations. They differ in the length of the periods when you allow yourself to eat or abstain from food.

With the 18:6 method, you fast for a full 18 hours; with the 20:4 method, you eat nothing for 20 hours. The 14:10 method, by contrast, is the easiest intermittent fasting approach. For example, you allow yourself to eat from 09:00 to 19:00, then eat nothing from 19:00 until 09:00.

The principle should now be clear.

2.3. 5:2 intermittent fasting

The 5:2 method is a slightly different type of intermittent fasting. You divide the week into five days when you eat your usual three meals a day and two days when you fast.

The basic idea behind 5:2 intermittent fasting is simple: on two days of the week, whether consecutive or not, you reduce your calorie intake to around 500 kcal.

For example, you could have two meals of 250 calories each. To manage that, you naturally need to eat an extremely high-fibre diet.

3. Is intermittent fasting healthy?

Apart from minor side effects such as hunger, stomach ache and low blood pressure, fasting has only benefits, as far as we know.

Fasting keeps the stomach empty for a longer period, giving it the opportunity to clear itself of residue. It is also absolutely beneficial to give the stomach a rest. Just as every athlete takes rest periods, we should have ‘rest periods from eating’. Intermittent fasting gives us these breaks in a positive way!

Studies also show that during long fasting periods the body starts consuming itself! It begins with the glycogen stores, which are also the first to be replenished when we eat. After more than 12 hours, fat cells or fatty acids begin to be burned, and after around 50–60 hours, damaged cells and proteins are broken down. This process is called autophagy.

Intermittent fasting, or fasting in general, can therefore be a powerful weapon against ageing and even cancer. It can also restore a better experience of hunger and fullness and a better understanding of how your body works. Not every stomach rumble needs to end in a snack, and you do not have to eat every extremely tasty meal until you are stuffed. Over time, you will realise that during most periods of your life you need far less food than you think.

3.1. Studies on the health effects of 16:8 intermittent fasting

Not all the study findings we list relate to the 16:8 intermittent fasting method, but it is the most widely used.

Numerous studies show that intermittent fasting is healthy, describing a reduction and normalisation of body fat, less inflammation and improved cell renewal. According to Mark Mattson, intermittent fasting is also said to reduce type 2 diabetes, heart disease and age-related neurodegenerative disorders.

1. Improved memory
2. Reduces oxidative stress and inflammation, similar to antioxidants
3. Improved heart health, including blood pressure and resting heart rate
4. Cell repair through autophagy
5. Fat loss while maintaining muscle mass
6. Reduced risk of type 2 diabetes and obesity
7. Possible protection of cells from cancer mutations
8. More resilient tissue that heals faster
9. Possible protection against Alzheimer’s, Parkinson’s and Huntington’s

In addition, studies show that animals’ lifespan can be extended by a double-digit percentage when they fast.

4. Intermittent fasting for sport and muscle building

Unfortunately, there are no studies examining the performance of athletes who have been practising intermittent fasting for years. All studies relate to short-term intermittent fasting or to Muslim athletes who do not eat during daylight hours in Ramadan. The most common intermittent fasting method used in studies is 16:8.

These studies show that intermittent fasting can affect sports performance both positively and negatively; the type of sport is decisive. For muscle building, intermittent fasting impairs weight gain from muscle, but not gains in strength. More detail is given in the following sections.

4.1. High-intensity training (HIT)

A study of high-intensity training (HIT) examined athletes’ sprint times during Ramadan. The results showed a significant reduction in speed.

A similar study examined the effect of three days of intermittent fasting on sprinters’ performance. It also found a drastic increase in running times and therefore a reduction in performance.

A reduction in performance during exercise was also found in cyclists following the 16:8 intermittent fasting method.

A longer-term Wingate test study, by contrast, shows that athletic performance returns to its initial level after around 10 days of intermittent fasting.

4.2. Endurance sport

A study carried out in 2018 found no negative or positive effects of intermittent fasting on performance during cardio exercise.

The endurance performance of cyclists was also studied, with the result of significantly lower performance.

By contrast, long-term experiments with mice showed a substantial increase in endurance performance.

Unfortunately, these mixed results do not allow a clear conclusion. Intermittent fasting therefore seems to have a negative or neutral effect on athletic performance. However, none of the studies examined the long-term effects on the body. Because of its positive effects on health, intermittent fasting could help maintain the body’s performance into old age.

4.3. Strength training, muscle building and intermittent fasting

The studies on muscle building and strength training during 16:8 intermittent fasting are much more promising, at least for those who want to gain strength, reduce fat and still stay ‘lean’.

Several studies concluded that intermittent fasting combined with strength training reduces the gain of new muscle mass while allowing strength gains and fat loss. This results in a generally more athletic physique.

5. What to eat during 16:8 intermittent fasting

The good thing about intermittent fasting, whether 16:8, 20:4 or another pattern, is that in general you can eat anything. Intermittent fasting is therefore not a specific diet but rather a schedule for when you should eat.

However, eating normally does not mean stuffing yourself with fried food and oversized portions of fast food during your eating windows. This would have just as negative an effect on your health as it would without intermittent fasting.

Here are some tips on what you can eat during 16:8 intermittent fasting and similar schedules:

1. Fruit
2. Vegetables
3. Rice, potatoes, pasta
4. Pulses
5. Meat, fish, eggs
6. Tofu, seitan, tempeh

Drinks you can have during 16:8 intermittent fasting and similar schedules (outside your eating window):

1. Tea such as guayusa tea (reduces feelings of hunger and keeps you alert without side effects)
2. Black coffee (not recommended because of its caffeic acid)
3. Coffee-flavoured tea (pleasant even on an empty stomach)
4. Green, black, herbal and fruit teas
5. Water

Avoid drinking the following outside your eating windows:

1. Coffee or tea with milk
2. Energy drinks
3. Juices
4. Soft drinks
5. Milk and alternatives
6. Anything that contains calories.

For more information, see our article ‘Intermittent fasting and drinking: what is allowed?’

6. Conclusion

Fasting, and particularly 16:8 intermittent fasting, seems to offer enormous benefits for our physical and mental health.

Studies into how healthy intermittent fasting can be show a clear improvement in overall physical condition. It can normalise blood pressure, reduce the risk of type 2 diabetes and stimulate cell renewal.

Intermittent fasting can also make a positive difference to your sporting performance if you maintain this eating pattern over a long period. With regular training, fat cells are reduced and muscle strength is built. However, intermittent fasting reduces muscle gain in terms of weight. This reduction in muscle building does not mean that existing muscle mass decreases; it stays the same. Rather, it means a decrease in the growth of new muscle mass, which can lead to a particularly athletic physique.