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How many hours of fasting should I do?

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Oh, the allure of fasting, a centuries-old tradition now glamorized by modern-day wellness gurus! When it comes to how many hours of fasting should I do, there isn’t a one-size-fits-all answer.

It’s like asking how many hours of sleep you need; it’s personal. However, a common starting point is the 16/8 method, where you fast for 16 hours and eat during an 8-hour window. The fasting journey is more than just a tick-tock of the clock; it’s about understanding your body’s cues.

So, shall we dive into the sea of fasting hours to find what suits you best? Spoiler: It’s an adventure filled with self-discovery and, hopefully, a happy tummy!

Key Takeaways

  • Fasting can be an effective weight loss strategy, but the number of hours you should fast depends on your goals and individual needs.
  • Intermittent fasting, such as the 16/8 method, involves fasting for 16 hours and eating within an 8-hour window.
  • Longer fasts, like the 24-hour or 48-hour fasts, may provide additional benefits but should be done under medical supervision.
  • Fasting can help reduce calorie intake, improve insulin sensitivity, and promote fat burning.
  • It’s essential to listen to your body, stay hydrated, and maintain a balanced diet to support overall health and sustainable weight loss.

Origin of voluntary fasting

Starting this article, I told you that fasting is in fashion, which is only half true.

Humans have fasted for most of our history because their food intake was intermittent. They depended on hunting and gathering, so they spent specific periods without finding food.

Once humans began to settle to practice agriculture and livestock, involuntary famine periods disappeared. Still, fasting periods were maintained in ancient cultures for what is known as voluntary fasting.

These were often called “cleansing,” “detoxification,” or “purification” times.

The earliest recorded stories of ancient Greece show a firm belief in its power.

Fasting has been the most respected healing tradition throughout the world throughout history. Over time, fasting lasted linked to religions.

πŸ‘‰ Fasting, for example, is widely practiced for spiritual reasons and remains a part of most of the world’s major religions. Three of the most influential men in the history of the world, Jesus Christ, Buddha, and the Prophet Muhammad, shared a belief in the healing power of fasting.

It is often called cleansing or purification in spiritual terms, but it practically refers to the same thing.

Benefits of fasting

how many hours of fasting you must do to get the results you want?

Unless you like historical data, so much history will not seem so relevant to you.

But there is something you should know: since these ancient times, our body has maintained the health effects of fasting.

πŸ‘‰ These benefits you will get from having a prolonged food restriction are:

  • Increases SIRT3, the youth protein, and reduces mortality.
  • Favors autophagy, another of our anti-aging systems, also in the brain.
  • Reduces indicators of inflammation.
  • Reduces triglycerides and improves the lipid profile.
  • Improves neuronal plasticity.
  • Improves insulin sensitivity and blood pressure.
  • Limits the growth of cancer cells and makes chemotherapy more tolerable.
  • Promotes weight loss while retaining muscle mass.

As you can see, many benefits exist, but not all appear with a 16/8 fast. For example, some of them require more than 24 hours without eating to take effect.

However, depending on which of these benefits you want to achieve, it may not be necessary to spend as much time fasting.

The optimal fasting dose is regulated by the desired benefits and the continuity of these intervals without eating food.

πŸ‘‰ For this reason, we have divided periods of intermittent fasting into three large groups, allowing me to understand how long I should help. These 3 groups are:

  • How many hours of fasting do I need to lose weight?
  • Or how many hours of fasting do I need to improve my metabolic disorder?
  • Or even how many hours of fasting should I do to improve the quality of aging and improve inflammation?

How many hours of fasting should I do to lose weight?

How many hours of fasting should I do to lose weight?

If something seems like common sense, our body understands that the best time to use reserves is when no food enters, and in fact, it is.

Surprisingly, the last 20 years’ weight loss recommendations have not gone this way, but quite the opposite, and have been based mainly on lowering calories and eating many times a day.

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Although this type of intervention can be useful in the short term when it comes to losing weight than others, they show an inexorable stagnation and a subsequent recovery of lost weight in the medium term. This relentless recovery occurs despite strict and continued adherence to the diet and regardless of the dietary strategy followed.

As this study shows, after 5 years of dieting, almost 100% of people have regained their weight, and 40% are heavier than before.

Ultimately, there are two clear facts:

  1. For the past twenty years, the usual recommendation for weight loss has been to eat less and exercise more.
  2. Over the last twenty years, the obesity rate has skyrocketed.
Obesity rate has skyrocketed

πŸ‘‰ Over time, we have been learning more about the mechanisms behind obesity, which, in summary, would be:

Processed products that make us eat more than we need: The food industry designs products so that my body wants to consume them even though it does not require the calories at the time

Excess carbohydrates: Associated with the first point, an excess of carbohydrates makes the body cells “saturate with so much sugar arrival.” they feel too full and close their floodgates to glucose entry. (They decide to fast until the pantries are empty).

The problem is that insulin and trying to force glucose into cells prevent us from using fat as fuel

This causes excess food to go more easily towards fat, and an increase in insulin appears to try to “push the sugar into the cells”). The problem is that insulin and trying to force glucose into cells prevent us from using fat as fuel. So we are filling the fat deposits and cannot use them.

Inflammatory context: Foods to which my body responds by inflaming: pollution, stress, lack of movement, or lack of sunlight are some of the situations that lead the body to be inflammatory. Inflammation hinders the function of insulin, an essential hormone in the obesity process.

And what does fasting have to do with all this?

When I fast, stop eating, stop confusing my brain with processed products, my insulin levels go down, and I create a context where my body has no choice but to use reserves to function.

And what dose is effective to achieve this:

Several human studies have shown that generating an intake window of about 10 hours without any dietary prescription already causes significant weight loss maintained after one year if the intervention is continued. Not only that, but they also had more energy throughout the day, rested better, and were less hungry at night.

πŸ‘‰ Therefore, a window of 10/14 already seems to help lose weight.

Of course, lengthening the fasting window will facilitate the adaptation of the appropriate metabolic context and accelerate the results.

If we observe this other study where we apply strategic fasting, 1 day of fasting, and other ad libitum food alternate.

  1. Fasting days are total. I cannot eat.
  2. The patient’s glucose levels were monitored to verify adherence to the program.

The results are as expected: Fat reduction, improvement of fat to lean mass, and improvement of cardiovascular markers.

What is very interesting about this study is the incredible adherence they achieved:

  • 90 people followed a 1-month intermittent fasting program, and only 2 people failed (or 97% adherence).
  • From this group, 30 people continued until 6 months, and ALL finished.

This level of adherence is unheard of.

Therefore we could conclude that if your goal is to lose weight, we will move in a range of:

  • Minimum effective dose: 10/14
  • Maximum dose: Fasting every other day.
  • Frequency: daily

How many hours of fasting should I do to improve metabolic disorders

The most common metabolic disorders can be:

Metabolic disorders: Insulin resistance and type 2 diabetes, and fatty liver

In this situation, we already find ourselves with an organism exposed to the aggressions of the modern world. The cells of the organs, mainly the liver, are full of fat. The body has been in a context where it cannot burn fat for so long that it will be difficult to convince it to do it again.

πŸ‘‰ In this situation, we have taken a step further to mere weight gain.

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Our physiology has begun to fail: Mitochondria and other cellular organelles make mistakes. Our DNA may have suffered some damage. It can make small errors in the manufacture of proteins or slightly change gene expression patterns.

To improve, we need to help our body mobilize the reserves again. However, we also have to regenerate our organs’ cells and empty those of the fat that they have accumulated.

The primary mechanism of cellular recovery is known as autophagy. This is a cellular recycling process where parts of the cell that have been damaged are digested to obtain energy or to manufacture these cellular fragments again without errors.

Therefore, it is essential to counteract the age-related accumulation of damaged organelles and proteins and improve cells’ metabolic fitness.


Autophagy even digests useless bits of DNA that are preventing the proper expression of genes.

In short, it is a highly conserved evolutionary process that cells activate to protect themselves from stress, learn from it, and improve.

Without a doubt, the most physiological way to induce autophagy that is phylogenetically conserved from yeast to primitive animals is nutrient deprivation fasting. A cell that is deprived of its energy supply, which may be the absence of Nutrients or the absence of growth factors. These are required for these nutrients that will destroy their bioenergy active. These are macromolecules, proteins, lipids, and ribonucleic acids for energy production.

In other words, the lack of energy in a cell is what activates it to make itself better.

But at the same time, the amount of fasting we need to activate autophagy is one of the great unknowns.

Ξ€he energy distribution in the organism is hierarchical

The key to all this is that the energy distribution in the organism is highly hierarchical. The more critical a system is to survival, the longer it takes to be sensitive to nutrient deficiencies.

The perhaps unfortunate example, but more visual, is the image we all have in mind of a child with malnutrition with a small body and a head that seems enormous. This is because the brain is the last organ to run out of energy.

In the case where we find ourselves where the liver is one of the most affected, we can be guided by the following data:

  1. Hepatic glucose stores last at least 24 hours
  2. The liver is one of the great controllers of our energy state, and what type of energy substrate is more coherent to use at all times.
  3. Given its antigenic exposure and its role in detoxification, the liver must always repair itself.

All this leads us to extrapolate together with some preliminary data on the induction time of autophagy in this organ:

πŸ‘‰ Minimum effective dose: Fasting 16 / 8- fasting every other day. Daily frequency

πŸ‘‰ Maximum Dose: Between 3-5 days of complete fasting or Fasting Mimicking diet. Monthly/bi-monthly frequency.

How many hours of fasting should I do to improve inflammation, neurodegenerative pathologies, and improve the quality of aging

Autophagy has also improved inflammation, stimulated the nervous system’s regeneration, and released neuronal growth factors. It is associated with increased life expectancy and quality of life.

In this situation, we are faced with prioritized systems at the energy level, and therefore, for them to be in deficit, we must “stress the body” a little more.

Although there are still no conclusive studies, it could be extrapolated from studies in mice that they would find signs of autophagy in immune cells 3-5 days after starting fasting. In turn, diets that simulate a 5-day fast have also seen significant modulating effects on the immune system.

Therefore, we need higher doses to generate effective changes at the systemic level that affect our body’s most relevant organs.

  • Minimum effective dose: 3 days
  • Maximum dose: 5 days.
  • Frequency 1 time every 1-2-3 months

As you have seen, we put the barrier in the 5 days. From our little data, it seems the moment we have already obtained all the desired effects does not involve high body wear and tear and is “relatively affordable to perform.

I do not want to emphasize that more extended fast studies are being carried out, but for the moment, it seems that 5 days is a reasonable limit.

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Benefits of Different Fasting Hours

Explore the various benefits associated with different fasting durations. Shorter fasting periods, like the 16/8 method, are sustainable and promote weight loss and metabolic health. Longer fasts, exceeding 24 hours, dive deeper into cellular repair and may enhance longevity. Understanding the unique benefits of different fasting durations can guide individuals in choosing a fasting method that aligns with their health goals.

Common Challenges in Fasting

Discuss common obstacles individuals may encounter during fasting, such as hunger, fatigue, and social or lifestyle disruptions. Offering practical solutions and tips to navigate these challenges can be immensely helpful. This section could provide readers with strategies to manage hunger pangs, maintain energy levels, and seamlessly integrate fasting into their lifestyles.

Success Stories and Testimonials

Incorporate real-life experiences and success stories from individuals who have practiced fasting. Sharing testimonials can offer readers diverse perspectives on the practicality and effectiveness of fasting for various hours. These stories can motivate and provide insights into the tangible outcomes one might expect from incorporating fasting into their routine.

Scientific Backing of Fasting Hours

Delve into the scientific research and studies that support the efficacy of fasting for different durations. Highlighting the science behind fasting can enhance the credibility of the information and help readers make informed decisions based on empirical evidence. This section could discuss how various fasting durations impact metabolism, weight loss, cellular repair, and overall health.


How many hours of fasting should I do?

Common methods include 16/8 or 18/6, but the right fasting hours vary individually based on health, goals, and tolerance.

What are the benefits of fasting?

Fasting may support weight loss, improve insulin sensitivity, and promote autophagy for cellular repair and regeneration.

Is fasting safe for everyone?

Fasting isn’t for everyone, especially for those with medical conditions or pregnant women. It’s essential to consult a healthcare professional before starting.

How should I break my fast?

Break your fast with nutritious and easily digestible foods to gently ease your digestive system back into action.

Can I exercise while fasting?

Yes, but listening to your body, modifying intensity, and ensuring proper hydration and nutrition during workouts is vital.

Conclusion: How Many Hours of Fasting Should I Do?

In summary, the article explored the world of weight loss foods and provided valuable insights on achieving weight loss goals without sacrificing taste. It emphasized the importance of incorporating nutrient-rich, low-calorie foods into your diet while staying informed and avoiding overprocessed foods.

Understanding the cornerstones of nutrition and the interplay between calories and macronutrients is essential for successful weight management. The article also debunked common myths surrounding weight loss foods and highlighted the significance of hydration in supporting weight management.

When integrating weight loss foods into your diet, practical tips such as meal prepping, mindful eating, and incorporating pre-and post-workout nutrition were discussed. The importance of a balanced diet, fitness, mental well-being, and lifestyle choices in the weight management journey was also emphasized.

In conclusion, achieving sustainable weight management is a continuous journey that requires learning, adaptation, and making informed choices. So, why not embark on this exciting adventure towards a healthier lifestyle? Start implementing these valuable insights today and take charge of your weight loss goals!

Ready to embark on your weight loss journey with knowledge of delicious and nutritious foods?

Discover the power of nutrient-rich, low-calorie options and make informed choices to achieve your weight loss goals. Remember, it’s not just about how many hours you fast but also about integrating a holistic approach to nutrition, fitness, and mental well-being. Start your exciting adventure now and embrace a sustainable and enjoyable path towards a healthier you!