What is Intermittent Fasting? The Ultimate Beginner’s Guide

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Intermittent fasting (IF), a widely adopted dietary pattern, which involves restricting food intake to specific hours of the day. Research suggests that its advantages go beyond weight loss, and that they may improve brain and heart health.

Intermittent fasting (IF) is currently one of the most popular health and fitness trends worldwide.

People are using it to lose weight, improve their health, and make their lives simpler.

Numerous studies show that intermittent fasting can have amazing effects on your body and brain, and it may even help you live a longer and healthier life. Study 1, Study 2, Study 3

Let’s take a look at the ultimate beginner’s guide to intermittent fasting.

What is intermittent fasting (IF)?

Intermittent fasting (IF) refers to a dietary pattern that alternates between periods of eating and fasting.

The focus isn’t on what you should eat, but rather the timing of your meals.

Looking at it from this perspective, it’s not traditionally a diet, but a more correct definition would be an eating cycle or eating pattern.

Popular practices of intermittent fasting usually consists of 16-hour fasts on a daily basis, or 24-hour fasts two times a week.

Fasting has been a major part of human evolution. Our ancestors, who were hunter-gatherers, didn’t have the luxury of constant food sources year-round like grocery stores or refrigerators. There were periods when they could find nothing to eat.

This led to the evolution of humans being able to adapt and function optimally even during extended periods without food.

Actually, fasting intermittently aligns naturally with our biology than consuming 3-4 (or even more) meals each day.

In addition to this, fasting is frequently done for spiritual or religious purposes, such as Islam, Christianity, Judaism, and Buddhism.

Intermittent fasting methods

There are numerous ways to intermittent fasting, all of which involve dividing the day or week into periods of eating and fasting.

During the fasting periods, your food consumption is either extremely minimal or nonexistent.

Here are the most common methods:

  • The 16/8 method: Also known as the Leangains protocol, this method involves skipping breakfast and limiting your daily eating window to 8 hours, for example, between 1–9 p.m. After that, you fast for the remaining 16 hours.
  • Eat-Stop-Eat: This method requires a 24-hour fast, once or twice a week. For example, you might skip eating by not eating from dinner one night until you eat dinner the following night.
  • The 5:2 diet: In this approach, you restrict your calorie intake to just 500–600 calories on two nonconsecutive days each week, while eating normally for the remaining 5 days.

All these methods induce weight loss by lowering your overall calorie consumption, as long as you don’t overeat during your eating periods.

The 16/8 method is often considered the most straightforward, manageable, and the easiest to follow and that’s why it’s the most popular.

How it affects your cells and hormones

During a fasting period, many changes take place within your body on the cellular and molecular levels.

For example, your body adjusts hormone levels to make it easier to access stored fat.

Cellular repair processes are also initiated, which change gene expressions.

Here’s a look at what happens in your body during fasting:

  • Human Growth Hormone (HGH): There’s a significant increase in the levels of growth hormone, as much as five times the normal rate. This contributes to various benefits, including fat loss and muscle gain, among others. Study 1, Study 2, Study 3, Study 4
  • Insulin: There’s a substantial improvement in insulin sensitivity, and insulin levels drop significantly. Lower levels of insulin help to access stored body fat easily. Study 1
  • Cellular repair: During fasting, cells start the process of cellular repair, including autophagy, where cells break down and remove old and dysfunctional proteins that have been build up within them. Study 1, Study 2
  • Gene expression: Changes occur in the functioning of genes associated with longevity and disease protection.

These changes in hormone levels, cell function, and gene expression are the ones who are responsible for the health benefits associated with intermittent fasting.

A tool for weight loss

Weight loss is often the main reason for individuals to experiment with intermittent fasting. Study 1

By limiting the number of meals consumed, can automatically decrease your calorie intake.

Furthermore, intermittent fasting adjusts hormone levels to help with weight loss.

It not only decreases insulin levels and boosts growth hormone levels, but it also increases the release of the fat-burning hormone norepinephrine (noradrenaline).

Thanks to these hormonal changes, short-term fasting could potentially increase your metabolic rate by 3.6–14%. Study 1, Study 2

By assisting in reducing calorie intake and boosting calorie burning, intermittent fasting tackles weight loss by changing both sides of the calorie equation.

Research found that intermittent fasting can be an extremely effective tool for weight loss.

A review study from 2014 discovered that this eating pattern can result in 3–8% weight loss over a period of 3–24 weeks, which is a significant percentage when compared to most weight loss studies.

According to the same study, individuals also experienced a 4–7% reduction in waist circumference, which is a significant decrease in harmful belly fat that surrounds your organs and causes disease.

A separate study conducted in 2011 revealed that intermittent fasting results in less muscle loss than the standard method of continuous calorie restriction.

However, it’s crucial to remember that the key to its effectiveness lies in the fact that intermittent fasting helps by reducing overall calorie consumption. If you overeat during your eating periods, you might not experience any weight loss at all.

Health benefits

A plethora of research has been conducted on intermittent fasting, including both human and animals.

These studies have demonstrated that it can offer significant benefits for weight control, health of your body and brain. It might even extend how long you will live.

Here are the primary health benefits of intermittent fasting:

  • Weight loss: As previously discussed, intermittent fasting can help with weight loss and reduction of belly fat, without the need for conscious calorie restriction. Study 1
  • Insulin resistance: Intermittent fasting can decrease insulin resistance, resulting in a 3–6% reduction in blood sugar levels and a 20–31% decrease in fasting insulin levels, which could potentially offer protection against type 2 diabetes.
  • Inflammation: Some research shows reductions in inflammation markers, which are a crucial contributor to many chronic illnesses. Study 1
  • Heart health: Intermittent fasting may decrease “bad” LDL cholesterol, blood triglycerides, inflammation markers, blood sugar, and insulin resistance — all of which are risk factors for heart disease. Study 1
  • Cancer: Animal studies suggest that intermittent fasting could potentially prevent cancer. Study 1, Study 2, Study 3, Study 4
  • Brain health: Intermittent fasting boosts the brain hormone BDNF and may help in the development of new nerve cells. It might also offer protection against Alzheimer’s disease. Study 1, Study 2, Study 3, Study 4
  • Anti-aging: Intermittent fasting has been shown to extend lifespan in rats. Studies demonstrated that rats subjected to fasting lived 36–83% longer. Study 1, Study 2

It’s important to keep in mind that research is still in its early stages. Many of the studies have been small, short-term, or conducted on animals. There are still many questions that need to be answered through more comprehensive, high-quality human studies. Study 1

Makes your healthy lifestyle simpler

Adopting a healthy eating lifestyle is simple, but sticking to it can be quite challenging.

A main issue is the effort required to plan and prepare healthy meals.

Intermittent fasting simplifies this process, as it reduces the number of meals you need to plan, cook, and clean up after.

This is why intermittent fasting is highly favored among individuals interested in life optimization, as it boosts health while simultaneously making life simpler.

Who should avoid it?

Intermittent fasting is not a one-size-fits-all solution.

If you’re underweight or have a past of eating disorders, it’s crucial to seek advice from a healthcare professional before undertaking fasting.

In such cases, fasting could potentially be harmful.

Should women fast?

There’s some evidence suggesting that intermittent fasting may not provide the same benefits for women as it does for men.

For example, a 2005 study found that while it improved insulin sensitivity in men, it led to a deterioration in blood sugar control in women.

While there are no specific human studies on this subject, older rat studies have shown that intermittent fasting can result in female rats becoming underweight, masculinized, infertile, and disrupting their cycles. Study 1, Study 2

Anecdotal reports have emerged of women whose menstrual cycle stopped when they began intermittent fasting, which resumed once they returned to their previous eating routine.

Due to these reasons, women should approach intermittent fasting with caution.

They should follow different guidelines, such as gradually adopting the practice and stopping it immediately if any issues such as amenorrhea (the absence of menstruation) occur.

If you’re experiencing fertility problems and/or are trying to conceive, it might be best to avoid intermittent fasting for the time being. Similarly, this eating pattern is likely not advisable if you’re pregnant or breastfeeding.

Safety and side effects

Hunger is the primary side effect associated with intermittent fasting.

You might also experience weakness, and your brain might not perform as per usual.

These effects could be temporary, as your body needs time to adjust to the new meal timing.

If you’re dealing with a medical condition, it’s crucial to consult your doctor before trying intermittent fasting.

This is particularly critical if you:

  • Have diabetes.
  • Struggle with blood sugar regulation.
  • Have low blood pressure.
  • Take medication.
  • Are underweight.
  • Have a history of eating disorders.
  • Are a woman who is trying to conceive.
  • Are a woman with a history of amenorrhea.
  • Are pregnant or breastfeeding.

Having said that, the safety profile of intermittent fasting is excellent. Provided you are overall healthy and well-nourished, there’s nothing dangerous about abstaining from food for a period of time.

Frequently asked questions – FAQ

Here are some answers to some frequently asked questions about intermittent fasting:

1. Am I allowed to consume liquids during the fast?

Yes. You can consume water, coffee, tea, and other non-caloric beverages. However, avoid adding sugar to your coffee. A small quantity of milk or cream might be acceptable.
Coffee might be especially helpful during a fast because it can curb hunger.

2. Isn’t it unhealthy to skip breakfast?

No. The issue is that many stereotypical breakfast skippers tend to have unhealthy lifestyles. If you ensure that you consume healthy food for the remainder of the day, then skipping breakfast can be perfectly fine.

3. Can i take supplements while fasting?

Yes. However, keep in mind that certain supplements, like fat-soluble vitamins, might be more effective if consumed with meals.

4. Is it okay to exercise while fasting?

Yes, workouts while fasting are fine. Some people suggest consuming branched-chain amino acids (BCAAs) before a fasted workout.

You can find numerous BCAA products on Amazon.

5. Will fasting lead to muscle loss?

Any weight loss approach can potentially lead to muscle loss, that’s why it’s crucial to engage in weight lifting and maintain a high protein intake. A 2011 study showed that intermittent fasting caused less muscle loss compared to continuous calorie restriction.

6. Will fasting lower my metabolic rate?

No. Earlier studies have demonstrated that short-term fasting can actually increase metabolism. Study 1, Study 2

However, longer fasts of 3 days or more can suppress metabolism. Study 1

7. Is it appropriate for kids to fast?

It’s likely a bad idea to let your child fast.

How to get started

It’s likely that you’ve already experienced many instances of intermittent fasting in your life.

For example, if you’ve ever had a late dinner and then didn’t eat until lunch the next day, you’ve likely already completed a fast of 16+ hours.

Some people naturally eat in this manner because they simply don’t feel the need to eat in the morning.

Many people view the 16/8 method as the simplest and most sustainable form of intermittent fasting — you might find it beneficial to start with this approach.

If you find this method easy to follow and you feel good during the fasting period, then you might consider advancing to more intensive fasts like 24-hour fasts 1–2 times per week (Eat-Stop-Eat) or limiting your intake to 500–600 calories 1–2 days per week (the 5:2 diet).

Another approach could be to simply fast when it’s convenient — occasionally skipping meals when you’re not hungry or don’t have time to prepare food.

You don’t have to follow a strict intermittent fasting plan to enjoy some of its benefits.

Feel free to experiment with different approaches and find a method that is enjoyable to you and that it aligns with your schedule.

Should you try it?

Intermittent fasting is not for everyone and is not mandatory.

It’s simply one of many possible strategies that can boost your well-being. Prioritizing a diet of real food, regular physical activity, and enough sleep remains of utmost importance.

If the concept of fasting doesn’t appeal to you, you can safely ignore this guide and continue with what’s working for you.

Ultimately, there’s no universal diet or nutrition plan that fits everyone. The most effective dietary approach for you is the one you can follow and stick to it over a long time.

While intermittent fasting works wonderfully for some people, it may not be suitable for others. The only method to determine which group you fall into is to give it a try.

If fasting feels right for you and it seems like a sustainable eating style, it can be an effective tool for weight loss and health improvement.

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