Table of contents
Fasting Training - What is it anyway?
Positive metabolic changes through fasting training
In this part we would like to look at the positive metabolic changes that can occur after exercising on an empty stomach. Especially in the last few years, many studies have dealt with this topic in detail, focusing on parameters of metabolism and muscle biochemistry in connection with insulin sensitivity and glycaemic control. The latter are closely related to diseases such as diabetes mellitus type 2 or insulin resistance. Some studies have shown that exercise training in a fasting state leads to an improvement in glucose tolerance and insulin sensitivity.
In patients with type 2 diabetes mellitus or insulin resistance, an increase in intramuscular (contained in the muscle) fat is often observed. This fat is stored in the form of intramyocellular triacylglycerols [IMTG]. Fasting exercise allows this to be removed more quickly and oxidised (converted into energy) more effectively. This seems to lead to better protection against insulin resistance. In addition, another study found that the reduction in fat mass triggered by fasting exercise can help improve glycaemic control.
A review shows that fasting exercise is associated with decreased blood insulin, increased blood free fatty acid concentrations, stable blood glucose concentrations (at least for the first 60-90 minutes), improved IMTG oxidation, increased fat loss while maintaining carbohydrate reserves. Long-term exercise in a fasting state can therefore improve insulin sensitivity and muscle fat oxidation. However, these preliminary results still need to be solidified in further studies. The above-mentioned metabolic changes through fasting exercise can therefore help to boost one's metabolism and prevent certain metabolic diseases, such as type 2 diabetes mellitus or insulin resistance.
If you are affected by one of these diseases and would like to try fasting training, please talk to your treating doctor beforehand to rule out hypoglycaemia during training.
You will learn how muscle fat oxidation works in detail and what influence fasting training has on it in a later section of this article.
Another good way to have a positive influence on your metabolism is intermittent fasting. You can find out how this works and what you need to bear in mind in this blog article: https://eagles.webseiten-werkstatt.eu/intermittierendes-fasten/
Guide to sober training
Intermittent fasting is a good introduction to fasting training if you schedule the fasting period in such a way that you skip breakfast, for example, and get a small workout in instead. In the beginning, endurance sports such as walking, jogging or cycling are best. After a few weeks, when you are a little more practised, you can also do low-intensity weight training. It is very important that you stay below the so-called "anaerobic threshold" during training so that the fat can be processed into energy in the form of ATP (the body's universal energy carrier). This metabolic process needs oxygen, i.e. it must be aerobic. In practice, this means that you should stay in low and medium intensity ranges where you are challenged and also sweat a little, but do not get too out of breath. Because then the body switches to a rather unfavourable anaerobic way of ATP production, which produces harmful lactate.
In addition, it is of great importance that between the individual training sessions you complete recover! The best way to organise your week is to exercise three times a week for at least 30 minutes each - in total you should be physically active for at least 150 minutes a week. In addition, you should not exercise for more than 60 minutes sober.
Nutrition during fasting training
This section is about what you should pay attention to in your diet. In order to activate the positive effects of fasting training, it is obvious to be really sober before training. This means no milk in your coffee or tea in the morning! However, calorie-free drinks such as water and unsweetened teas are allowed.
There is a lot to consider, especially when it comes to the selection of dietary fats: High-quality oils should be preferred, especially olive oil, as it contains a high proportion of monounsaturated fatty acids. Polyunsaturated oils such as linseed oil can also be used, but do not heat them and store them in the refrigerator and protect them from light. Other edible oils, such as sunflower oil, should be avoided because they undergo many more processing steps during refining. The result is that undesirable substances can get into the oil through numerous purification steps and valuable ingredients are lost (apart from the fact that sunflower oil has a high omega-6 content, which promotes inflammation). Also essential for the body are the so-called omega-3 fatty acids, which are particularly abundant in fatty cold-water fish (mackerel, salmon, herring).
If you don't like or don't want to eat fish, you can also use supplements made from seaweed to meet your daily needs.
Exercise and brain health
In addition to the positive influence that exercise can have on the metabolic processes in our bodies, exercise can also have a positive effect on our mental health. New research has shown that physical activity can also have an impact on brain health, leading to improved resistance to dementia, depression and stress.
It works like this:
The brain indirectly receives information about how much we move via the adipose tissue and the liver. Robust research over the last two decades has shown that skeletal muscle also performs secretory functions, i.e. that it is capable of releasing certain hormone-like messengers (myokines). These myokines help ensure healthy brain function. There is new evidence that these messengers (including cathepsin B) are able to cross the blood-brain barrier and thus promote memory and our ability to learn.
Furthermore, research suggests that another myokine (myokine IL-6), which is also released through exercise, may help to reduce our appetite. It follows that regular exercise, e.g. fasting exercise, could make an important contribution to the regulation of the feeling of hunger and satiety.
Another interesting aspect of regular exercise is that sport increases muscle expression of certain enzymes (kynurenine aminotransferases), thereby converting a neurotoxic amino acid (kynurenine) into an amino acid that protects the brain. Kynurenine is released more frequently during chronic stress and the accompanying depressive symptoms. Sport can therefore contribute to reducing the level of this neurotoxin and thus reduce depression-like symptoms.
Fasting training and sport
In the world of sport, this form of (endurance) training is about maximising the supply of energy from fatty acids in order to conserve the body's carbohydrate reserves, in the form of glycogen in muscles and liver. It also aims to increase the amount of fat metabolised per unit time (fat flow rate) during endurance exercise, as well as the rate of fat oxidation. To understand how this happens, we would like to explain how the body produces energy.
How does energy supply actually work in the body?
There are several ways for the body to produce energy. Adenosine triphosphate (ATP) is always produced, which is the body's main energy carrier. However, the organism does not have unlimited amounts of this available, but must constantly produce new ATP. This is done by splitting our main food components (carbohydrates, fats and proteins) in various metabolic pathways.
During prolonged exercise, the body's fat deposits (excluding the structural fats around the heart, kidneys, joints, etc.) are the most important and largest source of energy, as 100-200 times as much energy can be stored in fat tissue than in carbohydrate stores.
At the beginning of a workout, the body's own glycogen stores (= carbohydrate stores) in the blood, muscles and liver are first tapped for ATP production. However, this only works for a certain period of time; with continuous exertion, the body's own glycogen stores are exhausted and the body switches to producing energy from fats. This process can be supported by fasting before exercise, because this means that fewer carbohydrates are available to the body and it uses fat as the main fuel.
The most important place of fat storage in the human body is the white adipose tissue, where fat is available in the form of triglycerides in the adipocytes (fat-storing cells) for energy production. Especially during fasting training, the body draws on this energy source.
A high-quality study from 2011 was able to show that consistent fasting training over 6 weeks improves the energy supply from fats (fat oxidation) and increases the oxidation capacity of the muscles. This not only benefits athletes, but all of us and can improve our attention and concentration.
In addition, fasting exercise can prevent a drop in blood glucose concentration. However, the body's ability to break down carbohydrates remains in a healthy balance so that the optimal capacity for ATP production is maintained via the breakdown of carbohydrates. This appears to be related to increased degradation of intramyocellular triacylglycerols [IMTG], as this provides a rebuilding of ATP. In this way, the sparing of carbohydrate reserves during fasting training can be explained.
In this way, muscle contraction in the white muscle fibres can be ensured by carbohydrates at special moments of exertion, e.g. for final sprints or at short, high intensities.
Regularly practised fasting training therefore leads to positive metabolic effects in energy production. These include the increased release of free fatty acids from the adipocytes into the muscle cells and an increased fat oxidation rate with simultaneous preservation of carbohydrate reserves. More energy is then available in the muscle cells, which can increase endurance performance in the long term. This means that better training results can be achieved with the same load.
Another interesting aspect of fasting training is the improvement of carbohydrate metabolism. In order for the body to know how much energy it has available, it makes use of a certain enzyme, AMP-activated protein kinase (AMPK).
AMPK promotes resistance to oxidative stress and has a life-prolonging effect.
During fasting and subsequent fasting training, fewer carbohydrates are available to the body for ATP formation. This lack of energy is registered by AMPK. Furthermore, this enzyme causes more ATP to be formed from the remaining carbohydrates. In other words, the carbohydrate metabolism is optimised. However, this positive effect only occurs with long-term practice of fasting training, because first more mitochondria (power plants of the cells) and new transporters have to be formed. A review from 2018 showed that only fasting training stimulates the metabolic adaptations in the skeletal muscle and that a food intake before training cancels out these effects.
Fasting training in the high performance range
Of course, fasting training is also suitable for (high) performance. In order to achieve better training results, training on an empty stomach is a good idea because it leads to an increased fat oxidation rate while at the same time preserving carbohydrate reserves. In this way, endurance performance can be increased in the long term and better lap times can be achieved with a constant load (e.g. in a marathon).
However, other requirements apply to competitive and high-performance athletes, which we would like to explain here:
In contrast to health athletes, a higher protein intake (approx. 30% of total daily energy) with a simultaneous reduction in carbohydrate intake (approx. 50% of daily energy) and fat intake (approx. 20% of daily energy) should be taken into account. Sports nutrition products can be used to meet this increased need for protein. Another difference to health athletes is the training frequency. You should train at least 6 times a week (360 minutes in total) and increase the individual training sessions to at least 60 minutes. You can also increase the intensity of your training and train in the medium to high intensity range. In addition, (high) performance athletes do not need to recover completely before moving on to the next load phase. Incomplete breaks between training units are sufficient.
We would like to summarise the positive effects of fasting training once again at this point:
- Improvement of insulin resistance and glycemic control
- improved resistance to dementia, depression and stress
- positive metabolic effects in energy production
- increased release of free fatty acids from the adipocytes into the muscle cells
- increased fat oxidation rate while maintaining carbohydrate reserves - optimisation of carbohydrate metabolism
- better training results can be achieved with the same load
- Anti-aging and life-prolonging effect
Try it out and feel the positive effects of sober moving/exercising on your own body and mind. You can slowly approach it with an initially short duration of movement. Fasting exercise works particularly well in combination with intermittent fastingi.e. not eating for 13 to 16 hours at a time.