Intermittent Fasting Diet – Complete Guide For Beginners

An intermittent fasting diet (IF) is a very popular health and fitness trend that people are using to improve their overall health, lose fat, and make their lives simpler. There are studies that have found that an intermittent fasting diet can have positive health effects on your body, brain, and longevity.

Table of Contents


Intermittent Fasting vs. Daily Calorie Restriction for Type 2 Diabetes Prevention

Fasting: Molecular Mechanisms and Clinical Applications

What is the intermittent fasting diet?

Fasting has been practiced throughout human history. Our ancient ancestors didn’t have modern conveniences and vast amounts of food available. Which meant if they couldn’t find anything to eat, they didn’t. They fasted for periods of time and continued to exist.

Intermittent fasting (IF) is less of a diet and more of a pattern of eating that cycles between time periods of fasting and eating. With intermittent fasting, there isn’t a list of foods to eat or not eat. The focus is more about when you should eat. 

What’s the most common intermittent fasting diet plan?

While there are many ways to practice fasting, the most common intermittent fasting method is a 16-hour fast over a 24-hour period.

Which religions practice fasting?

Many people practice fasting for spiritual reasons. In fact, many of the world’s religions include fasting as a form of worship. Islam, Christianity, Buddhism, Judaism, and Hinduism, all practice some type of fasting as part of worship.

How much weight can you lose on an intermittent fasting diet?

One study found that you may be able to lose weight by approximately .55 – 1.65 pounds per week. Also, intermittent fasting can cause 3–8% weight loss over 3–24 weeks.

In the same study, people lost 4–7% of their waist circumference, which is an indication of visceral fat loss, harmful fat that builds up around your organs and is a major cause of many diseases.

Intermittent fasting diet basics

Since intermittent fasting doesn’t have a prescribed list of do’s and don’ts when it comes to foods, the basics are pretty simple. It’s not a diet. It’s more of a way of eating, or not eating. By understanding the different methods you can decide which one works best for you.

What are the different ways to do intermittent fasting?

There are many different ways to do intermittent fasting. Each method involves how much of the day or week you split into eating and fasting windows.

During the fasting window, you don’t eat. During the eating window, you do eat.

Here are the most popular ways to implement intermittent fasting into your life.

The 16/8 intermittent fasting diet method

In the 16/8 intermittent fasting method, 16 refers to the hours of the day you fast, and 8 is your eating window. 

The easiest way to do this method is to start your fasting window at 9 p.m., and then start eating at 1 p.m. the next day. The reason this is the most popular and sustainable method is that you are asleep for 7-9 hours of the fasting window. 

Eat-Stop-Eat intermittent fasting method

With this method, you fast for 24 hours, 1 – 2 days per week.

One popular example is from dinner one day until dinner the next day. But it’s flexible, you could go 24 hours from lunch to lunch or whatever works best for you.

The 5:2 diet

With this method, you only eat 500–600 calories on two non-consecutive days of the week but eat a normal amount of calories the other 5 days.

Each of these methods should cause weight loss, due to the intense caloric restriction, as long as you don’t binge on donuts during the eating window.

Alternate-day fasting

The alternate-day intermittent fasting is when you fast every other day, but you can eat whatever you want on the non-fasting days.

Some versions of alternate-day use a “modified” fasting strategy where you eat 500 calories on fasting days. 

Does the alternate-day intermittent fasting diet help you lose weight?

Yes. One study found that participants consumed 35% fewer calories and lost an average of 7.7 pounds after alternating between 36 hours of fasting and 12 hours of unlimited eating over a 4-week period.

Research shows that alternate-day fasting paired with endurance exercise may cause 2x weight loss than simply fasting alone.

The Warrior diet

Developed by Ori Hofmekler, the Warrior Diet is an intermittent fasting plan that follows the eating patterns of ancient warriors.

You eat very little for 20 hours during the day, then eat as much food as you want during a 4-hour window in the evening.

Warrior dieters consume the following in the 20-hour fast window.

  • Small amounts of dairy products
  • Hard-boiled eggs
  • Raw fruits and vegetables
  • Zero-calorie fluids 

After the fast, you can eat anything you want within a 4-hour window, given that it is unprocessed, healthy, and organic.

While there is no research on the Warrior diet, time-restricted fasting studies show there may be health benefits like diabetes prevention, delayed aging, and increased lifespan.

The Warrior Diet is more difficult to follow, as it restricts substantial calorie consumption to just 4 hours per day.

Is it unhealthy to skip breakfast?

No. The problem is that most stereotypical breakfast skippers have unhealthy lifestyles. If you make sure to eat healthy food for the rest of the day then the practice is perfectly healthy.

Can I drink liquids during a fast?

Yes. Water, coffee, tea, and other zero-calorie beverages are ok, and small amounts of milk or cream in coffee or tea may be okay. Don’t add sugar.

Coffee has actually been known to help with hunger pangs so it can be particularly beneficial during a fast.

Can I take supplements while fasting?

Yes, supplements are okay. But remember that certain supplements, like fat-soluble vitamins, are better taken with meals.

Can I work out while fasting?

Yes, fasted workouts are fine. Some experts recommend taking BCAAs before a fasted workout.

Benefits of the intermittent fasting diet

Many intermittent fasting studies have shown powerful benefits for weight management as well as the overall health of the body and brain. It may even help you live longer. The following are the major health benefits of intermittent fasting.

Weight loss is a major benefit of the intermittent fasting diet

Intermittent fasting can help you lose belly fat and lose weight overall, without having to restrict calories. Intermittent fasting also increases the release of the fat-burning hormone norepinephrine which may increase your metabolic rate by up to 3.6–14%.

Will fasting slow down my metabolism?

No. Studies show that short-term fasts actually boost metabolism. But, longer fasts of 3 or more days can suppress metabolism.

Fasting means you eat fewer and due to the hormonal and cellular changes, you burn more calories. Intermittent fasting promotes weight loss on both sides of the calorie equation. Studies show that intermittent fasting can be a very powerful weight-loss tool.

Will fasting cause muscle loss?

Most weight loss plans can result in some muscle loss. This is why it’s important to work out and eat lean protein. One study showed that intermittent fasting causes less muscle loss than the more standard method of continuous calorie restriction.

Fasting can help with insulin resistance

Intermittent fasting can lower insulin resistance and lower blood sugar by 3–6%. While in a fasted state insulin levels drop by 20–31%, which can lower the chances of type 2 diabetes.

Reduction in inflammation

A study shows reductions in markers of inflammation, which is a precursor of many chronic diseases. 

Lower risk of heart disease

According to studies, intermittent fasting may lower LDL cholesterol, blood triglycerides, blood sugar, and insulin resistance, which are all risk factors for heart disease (1, 20

Other studies

Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults

Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings

Cancer prevention

Animal studies suggest that intermittent fasting may help with cancer prevention.

Other studies

Intermittent fasting diet can help with cognitive ability

Intermittent fasting boosts the brain hormone BDNF, which may improve cognitive ability and may aid the growth of new nerve cells. It may also protect against Alzheimer’s disease.

Additional studies

Energy intake, meal frequency, and health: a neurobiological perspective

Dietary restriction normalizes glucose metabolism and BDNF levels, slows disease progression, and increases survival in huntingtin mutant mice

Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer’s disease

Fasting may help you live longer

Studies show that fasted rats lived 36–83% longer.

How does the intermittent fasting diet burn more fat?

The body requires energy. Fasting or not, your body needs the energy to function. The primary energy source in the body is glucose, which typically comes from carbohydrates, things like grains, dairy, fruits, certain vegetables, beans, and even sweets.

Both the liver and muscles store the glucose and release it into the bloodstream whenever the body needs the energy to function.

When fasting, this process changes. 

What is gluconeogenesis?

After 8 hours of fasting, the liver empties its glucose reserves and the body enters into gluconeogenesis, marking the body’s transition into fasting mode. This increases the number of calories the body burns and with no carbohydrates coming in, the body creates its own glucose using mainly fat.

When does the body go into starvation mode?

The body eventually runs out of energy and fasting becomes more serious in starvation mode. At this point, your metabolism slows down, and your body begins burning muscle tissue for energy. The true starvation mode only occurs after several consecutive days or even weeks without food.

So, for those breaking their fast after 24 hours, it is generally safe to go without eating for a day unless other health conditions are present.

What does the intermittent fasting diet do to your cells?

When you practice intermittent fasting, several things happen in your body on a molecular and cellular level.

Your body’s hormone levels make stored body fat more accessible. The cells themselves also begin important repair processes and change the expression of genes. Here are some changes that occur in your body when you fast:

Intermittent fasting can boost human growth hormone (HGH)

When fasting, growth hormone levels explode, increasing as much as 5x, which aids in fat loss and muscle gain.

Decrease in insulin

Levels of insulin drop as Insulin sensitivity improves. Lower insulin levels make stored body fat more accessible to be used for energy.

Cellular repair

When the body is in a fasted state, your cellular repair processes go into overdrive. This process of repair includes autophagy, where cells digest and remove old and dysfunctional proteins that build up within the cells.

What is gene expression?

Gene expression is when the coding in our DNA is converted into a functional product within the body, like a protein. Fasting activates gene expression which allows the cells to be more efficient in growth, longevity, and in their ability to protect against disease.

Changes in hormone levels, cellular function, and gene expression are responsible for the health benefits of intermittent fasting.

Fasting makes your life simpler

Eating healthy is simple, but like any diet, it can be hard to maintain over the long term. Intermittent fasting makes things easier. You don’t need to plan out your meals or cook.

Potential risks of the intermittent fasting diet

Intermittent fasting is not for everyone. If you have a history of eating disorders, you should not fast without talking with your doctor first.

If you have fertility issues or are trying to conceive, consider holding off on intermittent fasting for now. Fasting is also not a good idea if you’re pregnant or breastfeeding.

Side Effects of intermittent fasting

The biggest consequence or side effect that people have with intermittent fasting is naturally, hunger. You may feel physically weak. You may feel that your brain doesn’t perform as well.

These are typically only temporary effects. It can take your body time to adapt to the new meal schedule.

If you have any of the following medical conditions, you should consult with your doctor before trying intermittent fasting.

  • Diabetes
  • Issues with blood sugar regulation
  • Low blood pressure
  • Take medications.
  • Underweight
  • History of eating disorders
  • A woman who is trying to conceive
  • Women with a history of amenorrhea
  • Are pregnant or breastfeeding

That said, intermittent fasting is still very safe. There is nothing dangerous or harmful about not eating for short periods of time if you’re healthy and well-nourished.

Final thoughts on intermittent fasting

You may have intermittent fasted unknowingly at some time in your life. Eating dinner then sleeping in the next day and not getting around to eating until noon, that’s basically a 16/8 fast without even planning.

Many people consider the 16/8 method the simplest and most sustainable way of intermittent fasting. So that may be where to start.

If you try it and think it’s easy and you feel good during the fast, then maybe try moving on to more advanced fasts like:

  • 24-hour fasts 1–2 times per week (Eat-Stop-Eat)
  • Only eating 500–600 calories 1–2 days per week (5:2 diet)

There is no structured intermittent fasting plan, so experiment with the different approaches and find what works best for you and fits your schedule.

The bottom line, there is no one-size-fits-all solution for nutrition and health. The best diet for you is the one you can stick with for a lifetime. Intermittent fasting is great for some people, but others hate it. The only way to find out if it’s your thing is to try it out.

If you try intermittent fasting,  feel good doing it, and find it to be a sustainable way of eating, then go with it. It can be a very powerful tool for weight management and to improve your overall health.