【The Complete Beginner’s Guide】What Is Intermittent Fasting? Types, Benefits, How to Do It, and Why You Might Not Be Losing Weight, Explained Simply

“I failed at another diet… Nothing ever sticks for me anyway.”

Have you ever caught yourself thinking that?

If that sounds like you, there’s a method I really want you to know about.

It’s called intermittent fasting (IF).

The name sounds complicated, but what you actually do is simple.

You just decide on a “time when you can eat” and a “time when you don’t eat.”

In this article, I’ll walk you through everything: how IF works, how to get started, the benefits you can expect, and my own story of losing 15 kg (33 lb) in three months.

What Is Intermittent Fasting (IF)? Let’s Start With the Basics

Intermittent fasting (IF for short) is a way of eating where you set an “eating window” within the day and don’t eat outside of it.

“Intermittent” means “on and off” or “with breaks in between,” and in Japan it’s also known by names that translate to “periodic fasting” or “on-and-off fasting.”

When you hear the word “fasting,” you might picture some kind of grueling ordeal where you can’t eat anything at all.

But with IF, all you do is create a stretch of a few hours up to about 16 hours each day when you don’t eat.

Outside of that stretch, you can eat the foods you enjoy.

A Simple Way of Eating: Just Decide When You Eat

The most popular form of IF is the “16:8 method.”

You go 16 hours a day without eating and fit all your meals into the remaining 8 hours.

A typical schedule looks something like this:

You could even call it “just skipping breakfast.”

That alone gives you a 16-hour fasting window.

No Calorie Counting or Strict Food Rules, for the Most Part

One of the best things about IF is that you don’t have to tightly restrict what you eat during your eating window.

Of course, going overboard and binging is a no-go, but the core idea of IF is to focus on “when you eat” more than “what you eat.”

You don’t have to count calories at every meal or give up everything you love, which is a big part of why it’s so much easier to keep going.

Think of It as Giving Your Body’s “Store” a Closing Time

Every time food comes in, your body gets to work digesting and absorbing it.

If you eat three meals plus snacks and late-night bites, your body is like a “store” that’s open 24 hours and constantly busy.

Think of IF as giving that store a proper “closing time.”

Only once the doors are closed and no customers are coming in can the staff finally clean up the shop floor and sort out the inventory in the stockroom.

In your body, that “inventory” is your stored fat.

You don’t need to buy any special foods or gear, and you can start today, which is one of the reasons it’s getting so much attention around the world.

Why Does Your Body Change? How Two Habits Shift Your Metabolism

The reason IF changes your body is that “creating time without food” triggers two big shifts inside you.

Habit 1: 16 Hours Without Food Switches You Into “Fat-Burning Mode”

As long as there’s food (carbohydrates) available, your body prefers to use it as its main energy source.

But research shows that about 12 to 16 hours after a meal, the sugar in your body gets used up, and your body starts burning stored fat for energy instead.

It’s a lot like a hybrid car that switches over to its electric motor when the gas runs low.

Flipping this “fat-burning switch” is the single most important key to IF.

In other words, just by creating time without food, your body gets into a state where it burns fat more easily, without you having to do anything else.

When fat is broken down, your body also produces substances called “ketones,” which your brain and muscles can use as a backup fuel.

→ Learn more here: “Done While You Sleep: The Benefits of 16-Hour Fasting and How to Do It Right, Plus Is Coffee OK? Why You’re Not Losing Weight, and Precautions“

Another Benefit of Habit 1: Your Insulin Gets a Chance to Rest

When you eat and your blood sugar rises, your pancreas releases a hormone called “insulin.”

Think of insulin as a “warehouse keeper” that moves sugar from your blood into your cells and packs away any extra as fat in storage.

If you keep snacking, this warehouse keeper ends up working all day long, and your body stays stuck in fat-storing mode.

When you create time without food, the stretches without insulin get longer, making it easier to pull fat back out of the warehouse.

There are also research reports showing that giving this overworked warehouse keeper a break improved how well insulin works (insulin sensitivity).

Habit 2: Autophagy Kicks In and Resets Your Body at the Cellular Level

Autophagy is the process by which old cells repair and renew themselves.

It sounds technical, but put simply, it’s “your body resetting your cells from the inside.”

Yoshinori Ohsumi was awarded the 2016 Nobel Prize in Physiology or Medicine for uncovering how this process works.

Autophagy is known to ramp up once you’ve gone about 16 to 18 hours after a meal without eating.

That means IF isn’t just about losing weight. It’s also an effective approach for anti-aging and supporting your immune system.

“Getting healthier from the inside while you diet” is an especially appealing idea, particularly for women.

Anyone Can Stick With It! How to Start IF, With Sample Schedules

For those of you thinking, “Okay, I get the theory, but how do I actually start?”, here are the concrete steps.

A Recommended Schedule for Beginners

If you’re trying IF for the first time, I recommend the easy-to-maintain approach of “eating dinner a little earlier.”

If you finish eating at 8 p.m. and start again at noon the next day, your sleep counts toward your fasting time, so you’ll actually feel far less hungry than you’d expect.

If you go in with the mindset of “it’s basically just skipping breakfast,” you’ll probably find the bar is surprisingly low.

If jumping straight into 16 hours feels too hard, start with 12 hours and stretch it to 14 and then 16 hours every week or two. That way, it won’t be a strain.

What You Can and Can’t Drink While Fasting

Even during your fasting window, not every drink is fair game.

Drinking anything with calories will weaken the effects of your fast.

Staying well hydrated helps take the edge off hunger and makes it easier to keep going.

I go into detail on how to choose your drinks in “Choose These and You Won’t Go Wrong: What Can You Drink While Fasting? How to Choose Water, Tea, and Coffee, and Drinks to Avoid.”

Your First Meal After Fasting, and What to Eat During Your Window

If you break your fast by wolfing down fried food, sweets, or a big rice bowl, your blood sugar will shoot up.

Start with foods that are gentle on your stomach and less likely to spike your blood sugar, like miso soup, vegetable soup, salad, or boiled eggs.

Even though you can eat what you like, you’ll feel the benefits even more if you pay attention to protein from meat, fish, eggs, and soy foods, and fiber from vegetables, mushrooms, and seaweed.

That’s because if you don’t get enough protein, you’ll tend to lose not just fat but muscle too.

For help choosing foods to break your fast, also take a look at “How You Eat Makes the Difference: What Should Your First Meal Be After a 16-Hour Fast? Foods and Eating Order That Prevent Blood Sugar Spikes.”

The Main Types of Intermittent Fasting and How to Choose

Six Common Methods

There are several ways to do intermittent fasting, and they fall broadly into two groups: “limiting your eating hours every day” and “having days during the week when you barely eat.”

For Beginners, 16:8 Is the Top Pick

The most popular of these is “16:8,” where you go 16 hours without eating and have your meals within an 8-hour window.

Its big strength is that you can comfortably build in fasting time while mostly eating two meals a day, and it fits easily around work and family meals.

That said, if you normally eat breakfast, lunch, and dinner plus snacks, I don’t recommend jumping straight into 16 hours.

The way to avoid failing is to start with 12:12, then once you’re used to it, move to 14:10 and then 16:8, stretching the time like climbing stairs one step at a time.

Skip Breakfast or Eat Dinner Earlier: Which Should You Choose?

If you go with 16:8, you also need to think about where to place your 8-hour eating window.

If you’re not very hungry in the morning, or you want to have dinner with your family, the “skip breakfast” style, eating from 12 noon to 8 p.m., will probably be easier to stick with.

On the other hand, if you can’t give up late-night snacking or you’re a morning person, the “early dinner” style, where you finish dinner early, is a better fit.

Eating late at night is said to throw off your body clock, so ideally, try to finish dinner at least three hours before bed.

If you’re not sure which suits you, check out “A Schedule That Makes It Stick: How to Do 16:8 Fasting, Schedules for Every Lifestyle, Your 8-Hour Eating Window, and a 4-Week Starter Plan.”

Save 5:2 and Alternate-Day Fasting Until You’re Used to It

The 5:2 method, where you cut way back on food two days a week, and alternate-day fasting, where every other day you eat almost nothing, are methods where hunger tends to feel tough.

Intense hunger also makes it easy to rebound and overeat, so they’re not a good first choice for beginners.

It’s plenty to get your body used to things first with a daily time-limited method, and only consider these if that doesn’t feel like enough.

The Benefits You Can Expect From IF, and Precautions to Keep in Mind

Here’s a summary of the benefits many people notice when they keep up IF.

Results vary from person to person, but many people notice some kind of change within about two weeks to a month.

Five Changes You Can Realistically Expect

Among these, I hear “my blood sugar stabilized and I don’t get sleepy after meals anymore” and “my focus at work improved” a lot.

It’s not just for dieting. It’s a method I can recommend to anyone who wants to perform better day to day.

Some studies have also reported improvements in blood pressure, triglycerides, and markers of chronic inflammation in the body.

→ Learn more here (I share all the pros and cons of fasting, honestly): “Must-Read Before You Start: An Honest Comparison of the Pros and Cons of Fasting, Who It Suits, Who It Doesn’t, and How to Do It Safely“

What to Look At If You’re Not Losing Weight or Not Feeling Results

If you’ve been doing IF but aren’t noticing any change, these could be the reasons:

Your weight goes up and down daily because of things like water retention, so it’s important to look at changes over weeks rather than days.

When you’re just starting out, you may feel hunger, headaches, fatigue, or irritability.

Even if you hit a “plateau” where your weight stops dropping, be careful not to panic and slash your food intake drastically. That only backfires.

Check Before You Start! If This Applies to You, Talk to Your Doctor

For most healthy people, IF is a method you can practice safely.

However, if any of the following apply to you, please talk to a doctor or specialist before you start.

If you have any concerns about your health, don’t push yourself. It’s safest to talk to a professional first.

If you experience intense hunger, nausea, heart palpitations, or dizziness, stop right away and eat something.

Hunger Is Tough… Here’s the Fix! The Ultimate Support for Making IF Easy

“I’d like to try IF, but I’m worried about being hungry…”

I bet a lot of you feel that way.

To be honest, I felt the same way at first.

But after I started doing one particular thing, the hunger during my fasts became surprisingly easy to handle.

They’re not cheap, but I felt the results were worth more than the price, so I’m still using them today.

I especially want people who think “I don’t want to put in a ton of effort, but I do want real results” to give them a try.

Ways to Ease Hunger Without Supplements

If you’d rather not rely on supplements, I also recommend sipping water or tea regularly during your fasting window and taking a short walk in the morning to reset your mood.

More often than not, while you’re absorbed in something, the hunger fades on its own.

Hunger usually peaks and passes like a wave, so simply deciding “I’ll wait just 15 more minutes” can make it much easier to get through.

Doing it together with family or friends, or tracking your eating times on a calendar, can also keep you motivated.

On days when you’re short on sleep, your appetite hormones get thrown off and you feel hungrier, so getting a good night’s sleep is one more way to manage hunger.

Frequently Asked Questions About Intermittent Fasting

Start a Healthier Life Today With Intermittent Fasting

Intermittent fasting is a method anyone can easily work into their life. All you do is decide when you eat.

It’s a method I especially want people who say “I’ve been dieting for 10 years and nothing works” to try at least once.

There’s nothing complicated about it.

It makes it easier for your body to switch its fuel source to fat, gives your insulin a rest, and resets your cells through autophagy.

The appeal of IF is that you can make those changes happen in your everyday life, without any special tools or spending any money.

If 16 hours feels too hard right away, it’s perfectly fine to start at 12 hours and stretch it little by little.

Why not start today with just one rule: “No eating after 8 p.m.”?

If you want to make your fasting hours more comfortable, also check out this support information to help make fasting easier to stick with.

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