The power of fasting
Fasting and intermittent fasting have, as you surely know, become a popular lifestyle trend in recent years. Many studies show that fasting can have positive effects on, among other things, insulin sensitivity, energy balance, and recovery mechanisms in the body [1, 2]. However, a very important aspect is often overlooked: the difference between men and women. While men generally respond quite stably to fasting, a woman's hormonal cycle plays a significant role. This means that while fasting can offer benefits for women, it can also entail risks. In this blog, we'll delve into what fasting exactly is, its known benefits, different methods, the differences between men and women, and we'll provide practical tips.
What is fasting and what is intermittent fasting?
Fasting is as old as humanity itself. In the time of hunter-gatherers, food was simply not always available. Their bodies were accustomed to periods of scarcity and abundance. Religions also recognize fasting as an important ritual. Think of Ramadan in Islam, Lent in Christianity, or Buddhist traditions. Fasting is therefore not only a cultural tradition but also aligns with the natural rhythms of the human body.
Intermittent fasting (IF) is the modern translation of this. It's an eating pattern where you alternate between periods of eating and periods of fasting. The focus is therefore not so much on what you eat, but rather on when you eat.
What are the benefits of fasting?
Fasting can have various positive effects on your body and health. Firstly, it can help improve insulin sensitivity. This means your body can process carbohydrates from food more efficiently, which is beneficial for energy and preventing spikes and dips in your blood sugar. Additionally, fasting influences your metabolism. During fasting, your body switches to burning stored fat as an energy source, which helps maintain a healthy body weight. Because we can eat all day nowadays, our glycogen stores are continuously replenished. As a result, the body primarily burns carbohydrates instead of fat, and excess energy is stored as fat reserves. By fasting, your body gets the chance to restore this energy balance and relearn to switch to fat burning.
Fasting can also stimulate recovery processes in the body. During periods without food, your cells get the chance to clean themselves. Damaged components and waste products are then broken down and replaced by new, healthy components. This process is called autophagy and can be seen as a kind of bodily cleanse. Autophagy usually occurs after about 12 to 16 hours of fasting, when the body's glucose supply begins to run out and it switches to fat burning. This process supports cell renewal and can contribute to healthy aging.
Furthermore, research shows that intermittent fasting can lower blood pressure and has a positive effect on brain function and alertness. Fasting also reduces oxidative stress and inflammation in the body, which can lower the risk of chronic conditions such as cardiovascular disease and type 2 diabetes.
It's important to note that the effects can vary per person. Men generally respond quite stably to fasting. Women, on the other hand, may sometimes experience different results due to hormonal fluctuations. Therefore, it's wise to always tailor fasting to your own body and needs.
What are the methods of fasting?
There are various forms of intermittent fasting. The best known are:
16/8 method
A fasting method where you don't eat for sixteen hours and consume all your meals within an eight-hour window. For example, you eat between 11:00 AM and 7:00 PM, and then fast from 7:00 PM to 11:00 AM.
5/2 method
With this form of fasting, you eat normally for five days. On the other two days, you limit your calorie intake to a maximum of a quarter of your energy needs. These two fasting days should not be consecutive. For example, you choose Monday and Thursday.
Alternate day fasting
A form of intermittent fasting where you alternate between a day of normal eating and a day of fasting or severely restricted calorie intake (max. a quarter of your energy needs). Your weekly rhythm could look like this: Monday fasting, Tuesday normal eating, Wednesday fasting, and so on…
Full-day fast
With a full-day fast, you eat nothing at all for 24 hours. For example, you eat nothing from dinner until dinner the next day.
Prolonged fast
A prolonged fast is a fast that lasts longer than 48 hours. You eat nothing at all for 2 days.
Whichever form you choose, it remains important to ensure a nutritious and varied diet during eating periods. Especially within that limited time, your body needs to receive all essential nutrients.
What is the difference between men and women during fasting?
Firstly, it's important to understand that the cycles of men and women are entirely different. While men have a 24-hour cycle, women have an average 28-day cycle. The female cycle is divided into 3 phases: the follicular phase, which also includes menstruation (days 1-13), ovulation (day 14), and the luteal phase (days 15-28).
Different hormones dominate in each phase. For example, the main sex hormones (estrogen, progesterone, and testosterone) are lowest on day 1 of the cycle. In this phase, estrogen levels rise. Given a woman's hormone levels at this time, responsible fasting could be undertaken. This means longer fasts are possible. During ovulation, estrogen and testosterone dominate, allowing for moderate fasting. This could involve intermittent fasting of 16/8. After ovulation, it seems best for women not to fast.
During the periods when fasting can be appropriate for women, it's important to focus on good proteins and fats during your meals, while somewhat limiting carbohydrates. This is because the hormone estrogen is at its highest at that time. Estrogen functions best when there are as few blood sugar fluctuations as possible, so it's wise to reduce carbohydrates. During the other periods, it's good to eat meals that include a bit more fiber-rich carbohydrates. This could mean adding some sweet potato, seasonal vegetables, or extra fruit to your meals.
How do you prepare your body for a fast?
Make sure your last meal consists of enough proteins, healthy fats, and fiber-rich carbohydrates, so you don't experience strong blood sugar fluctuations and can therefore maintain the fast more easily. For example, you could consider a piece of wild salmon with quinoa and some seasonal vegetables. Avoid too much salt, as this can cause your body to retain fluid. Additionally, ensure you drink plenty of fluids in the days leading up to the fast to keep your mineral balance extra stable.
How do you break your fast?
For a short fast (less than 48 hours), you can immediately eat a complete meal. It's important to focus on a meal that is probiotic and protein-rich, but also contains good fats. This could be a good piece of meat fried in butter with some raw sauerkraut.
If you choose to fast for an extended period (+ 48 hours), it's important to break your fast responsibly. This is because fasting for 48 hours or longer is enough to significantly slow down your digestive system. You want to gradually reintroduce solid food to prevent stomach/intestinal discomfort. These four steps will make it easier for you to reintroduce solid food:
- Start with bone broth. After drinking a cup, it's important to wait an hour.
- Eat something probiotic and good fats. This could be some raw dairy. After eating, wait another hour.
- Add some fiber. It's important to choose cooked vegetables for this, and not raw salads. Wait another hour.
- You are ready to eat a complete meal. Make sure you eat enough protein to stimulate muscle growth.
When fasting is not advisable
Fasting is not suitable for everyone. For example, it is not recommended during pregnancy or while breastfeeding, as your body needs extra nutrients then. Also, if you have a low body weight or a predisposition to eating disorders, fasting is less advisable. People with low blood sugar or type 1 or 2 diabetes should be extra cautious. Additionally, it's important to be careful if you engage in elite sports or heavy physical labor. During intense exertion, your body needs a lot of energy and nutrients to perform well and recover. Prolonged fasting can deplete glycogen stores, which can lead to decreased strength, endurance, and concentration, and delayed recovery. The risk of muscle breakdown can also increase if insufficient energy and protein are available. If you have health problems or are taking medication, it is always wise to first consult your doctor to determine if fasting is suitable for you.
Practical tips
- Gradually build up to fasting and observe how your body reacts.
- Drink plenty of water, tea, and possibly coffee without additives. Consider electrolytes, especially if you fast for more than 14 hours.
- Avoid intensive workouts. Gentle exercise, such as walking and yoga, are often better during longer fasting periods.
- Avoid fasting during stressful periods, such as lack of sleep and high work pressure.
- Ensure you eat nutritiously during your non-fasting periods. This means adequate protein, good fats, and fiber-rich carbohydrates.
Book recommendations
- “Fast Like a Girl” by Dr. Mindy Pelz
- “The Dr. Ludidi Fasting Method” by Samefko Ludidi
References
[1] Vasim, I., Majeed, C. N., & DeBoer, M. D. (2022). Intermittent fasting and metabolic health. Nutrients, 14(3), 631. DOI: 10.3390/nu14030631
[2] Hales, C. N., Garland, P. B., & Randle, P. J. (1963). Newsholme EA: The glucose fatty acid cycle: its role in insulin sensitivity and the metabolic disturbances of diabetes mellitus. Lancet i: 7285¿ 7289. Doi: 10.1016/s0140-6736(63)91500-9
