If you keep up with health and wellness trends, you've probably heard the phrase "intermittent fasting" come up in recent months.
Intermittent fasting is more than a popular health and fitness trend – it is a dietary pattern that involves alternating cycles of fasting and eating.
What Is Intermittent Fasting?
Intermittent fasting is a dietary pattern – not a diet – that involves alternating cycles of fasting and eating.
The length of the cycles depends on what kind of intermittent fast you're participating in, but the concept remains the same.
Studies show that intermittent fasting can cause weight loss, improve your metabolic health, protect against disease and even, potentially, help you live longer.
Unlike a formal diet, intermittent fasting doesn’t focus much on the types of food or how much food you eat. It is all about when you eat.
Why Do People Fast?
Humans have been fasting for thousands of years – either due to a lack of food or because of religious reasons. In fact, many religions mandate or recommend some form of fasting.
Our bodies have adapted to periods of fasting, and are well equipped to handle it.
Many processes in the body alter themselves when the body is fasting, which have allowed humans to thrive when food wasn’t readily available.
Fasting has also been popular for many years as a way of burning fat and losing weight.
How Does Intermittent Fasting Work?
Intermittent fasting is fairly simple. Several methods or types of intermittent fasting exist, but they all have one basic principle in common – you stop eating for a period of time.
Many people already participate in intermittent fasting without realizing. Eating an early dinner, followed by a long night sleep and no breakfast the next morning actually qualifies as an intermittent fast.
If you’re one of those people who simply doesn’t feel hungry in the mornings and skips breakfast, you may already be intermittently fasting.
Because intermittent fasting has become very popular over the last few years, a few different “types” of intermittent fasting have emerged.
The different methods of intermittent fasting all split the day or week into eating periods and fasting periods, but the length of the periods differ from method to method.
So, if you do wake up and eat breakfast or feel hungry in the morning, there may be another form of fasting that would work better for you.
Lifestyle and nutrition coaches recommend trying a few different types of intermittent fasting and finding the one that is best for you.
The most popular types are:
- The 16/8 Method
- The 5:2 Diet
- Alternate-Day Fasting
- The Warrior Diet
- Spontaneous Meal Skipping
The 16/8 Method
The 16/8 Method of intermittent fasting is the most common method out there.
If you are following the 16/8 Method, that means you are only eating within a window of eight hours every day and not eating during the remaining 16 hours. Some people will only eat in a smaller window of six or eight hours.
For example, if you eat your first meal of the day at noon and then eat your last meal by 8 p.m., you will be fasting for 16 hours between meals.
Many people who already skip breakfast find this to be the easiest way for them to try intermittent fasting. If you wake up hungry and usually eat a large breakfast, you will struggle a little bit more with this form of intermittent fasting.
The Eat-Stop-Eat method is fairly simple: Once or twice a week, you fast for a full 24 hours.
For example, if you eat dinner at 6 p.m. on a Monday and then don’t eat again until 6 p.m. on Tuesday, you’ve done a full 24-hour fast. You can start your fast and end it at any time, as long as it is 24 hours.
It is very important that if you are participating in the Eat-Stop-Eat method of fasting, you are eating normally during the days between fasts and that you do not fast on consecutive days.
The 5:2 Diet
The 5:2 Diet is also known as the Fast Diet, and unlike some of the other fasts, it does not involve going long periods without eating anything.
When participating in the 5:2 Diet, you eat normally 5 days of the week and then eat around 500 to 600 calories on the other two days of the week.
Women should eat 500 calories and men should eat 600 calories.
Alternate Day Fasting
There are several ways to participate in alternate day fasting, but the general idea is that you fast every other day.
Some methods of alternate day fasting allow about 500 calories during the fasting days.
This is a more extreme form of fasting, so if you are new to intermittent fasting or fasting of any kind, this may not be the right method for you.
The Warrior Diet
The Warrior Diet allows people participating to undereat during the day and overeat at night. It is based off of the ways of the “ancient warrior,” who had little to eat during the day but ate their hunt at night.
People who are participating in the Warrior Diet eat small amounts of raw fruits and vegetables or nothing at all during the day. Then, they eat one huge meal – a “feast” – at night.
This method also recommends eating foods that are raw, whole and unprocessed.
Spontaneous Meal Skipping
If you aren’t a fan of structure or schedules, spontaneous meal skipping might be the best for you. You don’t need to follow a specific intermittent fasting method or program to reap the benefits.
If you don’t feel hungry or are too busy to cook or eat, skip a meal when you feel so inclined. This, when you do it once or twice, amounts to a spontaneous intermittent fast.
What Can I Eat While I’m Fasting?
While you are fasting, it is recommended that you don’t eat any food at all.
Water, black coffee and other non-caloric beverages are OK during most methods of intermittent fasting. This can also help you to feel less hungry.
When you are in an eating period, it is important that you are eating healthy foods and eating normally.
Some methods of intermittent fasting specifically recommend whole, unprocessed foods. Other methods recommend following the ketogenic diet.
To make sure you get the most out of your intermittent fast, most recommend that you eat normally during your eating periods – meaning not binge eating or gorging yourself to make up for the time you went without food.
Benefits of Intermittent Fasting
There are many evidence-based health benefits to intermittent fasting, and a lot of research has been done on the topic in the last few years as it’s become more popular.
A few of those health benefits include, but are not limited to:
- It actually changes how your cells, genes and hormones function.
- It can help you burn fat.
- It can lower your risk of Type 2 Diabetes.
- It may help you live longer.
- It’s good for your brain.
- It can reduce oxidative stress and inflammation.
Intermittent Fasting Changes Body Processes
When your body enters fasting mode, several things can happen.
Insulin levels drop, while growth hormone production increases, which facilitates fat burning and muscle gain.
Your body also begins a cellular repair process, which helps rid your cells of waste.
Intermittent Fasting Helps You Burn Fat
Most people who participate in intermittent fasting do it to lose weight and burn fat.
Research shows that people who follow intermittent fasting for up to 16 weeks can help prevent obesity.
Intermittent Fasting Lowers Your Diabetes Risk
When your body is fasting, it reduces blood sugar levels, which in turn, reduces insulin resistance. This protects your body from developing type 2 diabetes.
Some research shows that intermittent fasting can also stop diabetes while it’s developing and reverse it.
Intermittent Fasting May Help You Live Longer
Research shows that intermittent fasting manipulates the energy-producing mitochondria of your cells, which then increases your lifespan.
In one study, rats that fasted every other day lived 83% longer than rats who weren’t fasting.
Intermittent Fasting is Good For Your Brain
Many people in this field agree that one of the most likely benefits of intermittent fasting is the promotion of healthy brain function.
This works by forcing your body to burn more fat instead of sugar, which then produces ketones. Ketones boost energy and help you think more clearly.
Intermittent fasting can also ward off diseases like Alzheimer’s and Parkinson’s.
Intermittent Fasting Reduces Oxidative Stress and Inflammation
Chronic, long-term inflammation can lead to all sorts of common diseases. And oxidative stress is connected to aging and many other diseases.
Intermittent fasting enhances the body’s resistance to oxidative stress and fights inflammation, which helps your body avoid many diseases and fight the effects of aging.
Is Intermittent Fasting Right for Me?
Intermittent fasting is not right for everyone.
If you are struggling to lose the last few pounds before you hit your goal weight or you are prediabetic, intermittent fasting might be the right way to jumpstart your body.
Intermittent fasting is also a good fit for people who want to fight the effects of aging.
Many benefits of intermittent fasting that have been researched help the body ward off the effects of aging, as well as increase brain function.
If you don’t like the idea of fasting, that’s OK. Fasting isn’t for everyone, and there are many ways to burn fat and live a healthy lifestyle that don’t involve intermittent fasting.
Who Shouldn’t Intermittent Fast?
There are a few situations where intermittent fasting might not be the right fit for your body, or it might even be harmful for your body.
If you are concerned about intermittent fasting impacting any of your medications or currently diagnosed medical issues, always consult a doctor before beginning.
Intermittent fasting is not a good fit for you if you...
- Are pregnant or plan to become pregnant.
- Have a history of disordered eating.
- Experience chronic stress or don’t sleep well at night.
- Are new to diet and exercise.
Avoid Intermittent Fasting If You’re Pregnant
Unless your doctor has told you otherwise, pregnancy (or if you are planning or trying to become pregnant) is not the time to worry about losing weight and burning fat.
Pregnant women have extra energy needs, so this is not the time for intermittent fasting. You may also want to consult your doctor about intermittent fasting if you are breastfeeding.
Avoid Intermittent Fasting If You Have A History of Eating Disorders
If you have struggled with an eating disorder in the past or currently have an eating disorder, you should steer clear of intermittent fasting.
The periods of eating and fasting could be a psychological trigger for your eating disorder.
Avoid Intermittent Fasting If You’re Stressed or Don’t Sleep Well
If you are experiencing chronic or severe stress, intermittent fasting is not for you – at least not during this period in your life. The same goes if you aren’t sleeping well or have a history of sleeping issues.
Your body needs additional energy and care during this time, so taking away energy during the day or for specific periods would be unwise.
Avoid Intermittent Fasting If You’re New to Exercise and Dieting
If you have never been one for exercising or dieting in the past, intermittent fasting may be tempting but probably isn’t the right fit for you.
After focusing on your diet and insuring your body is getting the right nutrients, then intermittent fasting might be a good fit for you.
Side Effects of Intermittent Fasting
One of the main side effects of intermittent fasting may be obvious: As your body adapts to the new schedule of eating and fasting, you’re going to feel hungry.
You may also experience weakness or even brain fog.
If you have a medical condition such as diabetes or low blood pressure, or if you take medications that require you to eat or regulate your diet, you should consult your care provider before beginning intermittent fasting.
Intermittent fasting has been proven to be safe for many people, but it is not right or safe for all people.