Intermittent Fasting 101 – A Complete Beginner’s Guide

By now I’m sure you’ve heard of this new dieting trend call intermittent fasting.

It’s a diet intervention that has been taking the health and fitness industry by storm. 

Bodybuilders and fitness buffs alike are praising intermittent fasting because of its ability to burn fat and lose weight quickly without counting calories and eating any specific types of foods. 

So if you’ve been reading about intermittent fasting but aren’t sure if it’s right for you, or don’t know how to get started, you’ll find answers here. 

This beginner’s guide is on what intermittent fasting is and how you can use it to lose weight fast, burn fat, and improve your overall health. 

Hence, this is your ultimate beginner’s guide to intermittent fasting.

What Is Intermittent Fast aka IF?

According to Wikipedia, intermittent fasting is an umbrella term for various diets that cycle between a period of fasting and eating.

It’s not about what foods to eat and what macro ratios you should base your diet on. 

Rather, it’s about when to eat and when not to. 

In a sense, it is more of an eating pattern than a conventional “diet” per se. 

In fact, you could eat fast foods during the eating period and not break the IF rules. 

There are many variations of IF cycles around, but here is how the most popular one works. 

Fast for 12-16 hours a day from dinner to lunch the next day with a schedule like:

  • Dinner: 8 pm Mon.
  • Fast: 9 pm Mon. to 12 am Tue.
  • Lunch: 12 am Tue.

Depending on which method, the period of not eating can be anywhere from a few hours up to a few days. 

All depends on which fasting methods you’re following and the purpose of doing the IF. 

The takeaway: Intermittent fasting is simply a short-term fasting technique where you limit your eating to a restricted period of time and allow your body to fast for the remaining window of time. It’s not a diet nor a food list. Rather, it’s an eating cycle and pattern that designate when to eat and when not to.

So Why Fast?

People fast for various reasons, and humans have fasted for centuries.

Some out of necessity while others out of religious belief. 

When we feel sick, we unintentionally and instinctively fast for a period of time. 

So the fasting concept is nothing new.

And our bodies are clearly equipped to handle a short-term fast. 

But why try fasting if it’s not for religious reasons, sickness, or lack of food.

It’s because intermittent fasting carries mounts of health benefits.

This is because major shifts happen in your body on the cellular and hormone level when you fast. 

To start, fasting allows the body to switch its primary energy source from glucose to fat. This shift singlehandedly produces major health benefits (1). 

Your stored fat is merely energy fuel for your body waiting to be used. By fasting and starving your body off on food energy, glucose, you allow your body to burn off the stored fat for energy. 

Along with this, there are additional changes that happen internally:

Increased Growth Hormone: Fasting increases human growth hormone level as much as 5 times (23). This aids fat loss as well as muscle gain (4).

Lower Insulin: IF decreases your insulin level and increases lipolysis—the breakdown of fat. This makes excess, stored fat more accessible to use as energy (5).

Gene expression: There are changes in the function of genes related to longevity and protection against disease (67).

All these changes lead to phenomenal health benefits like: 

Weight Loss: Weight loss relies on calorie deficits. You lose weight when you simply eat fewer calories than you burn. Intermittent fasting makes it easier to eat fewer calories without counting calories by limiting meal counts and eating time (8). 

Prevents Type 2 diabetes: IF reduces insulin resistance by drastically lowering blood sugar levels. This prevents you from developing Type 2 diabetes (9). 

Reduces Inflammation: Research shows IF reduces oxidative stress, which leads to reduced inflammation (10).

Reduces cancer risk:  Several animal studies have shown a link between reduced breast cancer risk and intermittent fasting.

Anti-aging: In rat studies, IF boosted longevity by up to 83%. Not only that, IF’s effects on oxidative stress also leads to slow down in aging (11). 

The takeaway: Due to many cell and hormone level changes IF brings, you can experience countless phenomenal health benefits. By fasting for just 14 hours a day, you can increase your fat burn, lose more weight, boost brain power, prevent major diseases, and slow down aging, all without making any other changes to your lifestyle or counting calories. 

Who Should Avoid Intermittent Fasting?

Since it’s so beneficial to your overall health profile to fast daily, why shouldn’t anyone do it? Should it be for everyone?

Generally speaking, there is no particular danger to not eat for a short period of time if you are well nourished and healthy. And Intermittent fasting does have a phenomenal safety profile. 

But there are a few exceptions.

Avoid IF if…

  • You are pregnant or breastfeeding.
  • You have a history of an eating disorder 
  • You have low blood pressure.
  • You are on medications.
  • You are underweight.
  • You are a female with a history of amenorrhea.
  • You are a female trying to conceive.
  • You have a certain medical condition 

Common side effects you may experience would be hunger and loss of calories from skipping a meal. If you are not meeting your caloric needs as of now, intermittent fasting may not be for you. 

If you also don’t manage hunger well, this may not be for you. 

When in doubt, consult with your physician first before starting intermittent fasting. 

Got Questions Before You Start?

Here are some frequently asked questions about intermittent fasting. 

Below, you can find answers to the FAQs of intermittent fasting.

1. What can I drink during the fast?

Any non-sugary, non-caloric drinks are ok to drink. That includes coffee, unsweetened tea, and water. 

Coffee and tea can be particularly beneficial during a fast as it may blunt hunger and increases fat burn. Avoid any sugary drinks, fruit juices, and sweetened coffee and tea. 

2. How can skipping breakfast be healthy?

Breakfast has long been perceived as the most important meal of the day. But it doesn’t have to be. In fact, every meal is important. 

And your morning fuel for the body does not have to come from food energy. Most of us have stored fats the body can use to fuel us through the morning, and which is the whole point of IF.  

But since lunch will be your first meal of the day, I advise that you eat a well-balanced lunch. 

3. Can supplements be taken while fasting?

Yes, you can take vitamins when you are fasting though some vitamins are better taken with meals. Check the label and follow the instructions there. 

4. Can I work out while fasting?

Yes, working out while fasting can actually help you burn more fat and lose weight faster.  In fact, some research shows a workout before your first meal increases fat burn and boosts metabolism by 20% (12).  

5. Will I lose muscle mass while fasting?

Yes, but there are a few ways to overcome this. Stay on a high-protein diet and lift weights to build lean muscles. 

Research shows that being on a calorie-restricted diet causes more muscle loss than intermittent fasting (13).

6. Will fasting slow my metabolism?

No, it shouldn’t.

Multiple studies show short-term intermittent fasting can in fact ups your metabolism not slows it down (1415). However, fasting that lasts 3 days or longer can slow your metabolism (16). 

7. Can I fast while on a diet?

Yes, since intermittent fasting is an eating pattern rather than a diet, you can do it while being on a diet.

However, I advise you review your daily calorie intake and modify it if skipping one meal will result in an unhealthy calorie deficiency. 

Generally speaking, whether you’re on the Paleo diet or the high-fat, low-carb keto diet plan, intermittent fasting can increase the effectiveness of most diet.

How to Start Intermittent Fasting

There are several patterns and methods of intermittent fasting all consists of periods of eating and not eating. 

Here are the most popular ones around: 

The 16/8 Method: Fast for 16 hours at a time in a day and eat within the remaining 8 hours. For example, fast from 8 pm to noon that next day. Eat from noon to 8 pm. 

The 24 Method: Fast for 24 hours at a time only once or twice a week. For example, you fast from 8 pm at night to 8 pm the next night. 

The 5:2 Method: Two days a week, limit eating to 500 calories a day. 

There are countless more variations. 

The simplest and easiest method I find is the 16/8 method. It’s effortless to stick to and easiest to create a lifestyle around. 

In fact, before I intentionally started the 16/8 intermittent fasting,  I was already naturally eating this way. I don’t usually have too much time for breakfast, so I skip and just have a glass of water (now ACV drink is my go-to). 

My lunch at 1 pm is my first meal of the day. 

Then I eat my last meal somewhere around 7 pm, so I end up instinctively fasting for 16–19 hours every day.

So, Should You Try Intermittent Fasting?

That depends on your lifestyle, health status, and goal.

It’s not a must to have a healthy life. It’s one lifestyle strategy that can easily boost your health. 

It’s not built to be a replacement for other healthy habits nor it’s meant to be paired with any particular diet. 

If you already have a set of health regimens, great! Add IF to it to rev up your health even more!

Or, it may be that you find other healthy changes hard to implement and impossible stick to.

If that’s you, intermittent fasting provides an effortless way to start one habit that’ll boost your health.

In fact, IF is actually very popular amongst life hacking aficionados for how it painlessly improves one’s health all while simplifying life. 

Either way, eating healthy foods, working out, and getting quality sleep are still are the core of what builds a healthy body.

All in all, nutrition and healthy does not come with one magic pill or the solution is ever one-size-fits-all. The most suited one for you is usually the one you can stick to. 

This makes IF a natural fit for some, but not for others. The best way to find out if it’s for you is to try out! 

If you regularly skip breakfast out and feel great when fasting, then intermittent fasting can be a powerful strategy to lose weight and improve your health.

Misato Alexandre


After making healthy living a priority, Misato lost over 20 lbs in less than 90 days. Instead of weight loss being a dreading experience, living the lifestyle of health and fitness granted her more happiness and joy than ever before. She co-founded Fitwirr to make health and fitness simple for everyone and share her tips through writing evidence-based articles on nutrition, weight loss, and exercise.

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