Intermittent Fasting: What It Is and Why You Should Get Started Now

This article was published on: 03/30/22 6:03 PM

Reading Time: 11 minutes

Intermittent fasting is an eating plan that switches between fasting and eating on a regular schedule. Intermittent fasting is about when you eat rather than on the usual diet focus of what to eat. With intermittent fasting you eat during a specific time frame. Fasting this way can help your body burn fat and gain other health benefits as well. But how do you do it? And is it safe?

intermittent fasting includes eating healthy foods

Fascinating History of Breakfast

It’s fun to shine a light and look back in time and see what people thought about such common acts as eating breakfast and fasting.

Did you know that during the 13th century it was a generally held belief that eating breakfast was an act of gluttony? Eating breakfast was one of the seven deadly sins.

You might be wondering where such a rigid belief came from. It came from a Catholic priest and theologian, Thomas Aquinas, who wrote an influential book, Summa Theologica. Aquinas wrote that eating breakfast leads to “praepropere,” a Latin term in English meaning acting in haste.

His influence led to Catholics believing that being overhasty about breaking your fast led to other “lusty” appetites such as drinking alcohol to excess.

Eating before 10:30 or 11 a.m. meant you were morally weak. Breakfast was only acceptable for children, the sick and elderly, or laborers needing energy for work.

Doctors of that time period began advising that eating early in the morning was harmful. Their hypothesis was that the previous day’s large meal needed more time to properly digest.

In Aquinas’ day, most folks ate their large meal in the pre-noon hours, followed by a lighter meal about five hours later.

Changing Attitudes Towards Breakfast

By the 1500s, attitudes began changing, and in some cases breakfast became the norm.

Meat, butter, and caffeine made eating breakfast more appealing, especially for wealthier people.

In 1602, a British physician and civil lawmaker named William Vaughan made it official. His education manual, Natural and Artificial Directions for Health, stated that people should “eat three meals a day until you come to the age of 40.”

Current Ideas About Breakfast and Fasting

Fast forward to today when breakfast is being touted as the most important meal of the day. I’ll give you three guesses where this message originated from. Did you guess cereal companies? Clearly they have a good motive for staking their claim.

However, science advises against basing our meal schedules on William Vaughan and the cereal marketers. The better approach is closer to the teachings of Thomas Aquinas.

The Science Behind Intermittent Fasting

Are you aware that more than 40% of American adults are considered obese and nearly 30% of adults 65 and older are obese? This increases risks for health problems such as heart disease and Type 2 diabetes.

However, there continues to be a growing body of research supporting the idea that going a certain amount of time without eating provides many health benefits.

Let’s take a closer look and see what happens in your body when you eat and when you fast.

When you eat, you take in food and break it into usable energy in the form of glucose. Once that glucose gets into your bloodstream, it travels to cells and keeps them running. The transfer of glucose from blood to cells is facilitated by the hormone insulin.

If you have more glucose floating around than your body immediately needs, insulin tells your body to store the excess. It’s transported to your liver and muscles, where it’s stored as glycogen.

But if your liver is full of glycogen, your body turns the excess glucose into fat.

If you take in too many calories or eat too frequently, your insulin levels stay elevated. Over time, high insulin levels cause your body to stop responding well to insulin. This is called insulin resistance.

With insulin resistance, sugar stays in your blood for longer periods of time, not getting stored as glycogen or fat. This leads to high blood sugar, a hallmark of diabetes. Sugar molecules floating around in excess lead to inflammation as well.

When you fast, your body reverses the process!

Your body doesn’t stop needing energy. It still needs energy to keep running. The easiest way to create that energy is to break down the liver’s stored glycogen. Once glycogen reserves get low (because you’re not actively metabolizing new foods into glucose), the liver starts breaking down stored fat. The energy from fat becomes molecules called ketones. The process of breaking down fat for energy use is called ketosis.

So let’s unpack this science and see what it amounts to.

Benefits of Fasting

One of the benefits of fasting is it keeps your insulin levels low. With less insulin, you’re in energy-burning mode instead of energy-storing mode. The longer you stay in that mode, the more fat you burn.

Another benefit is that keeping insulin levels low improves your body’s sensitivity to insulin.

When you fast intermittently, you train both your brain and body to source energy from fatty acids and ketones, in addition to carbohydrates, glucose, and glycogen. This is called metabolic switching, and it happens in two phases: glucose to ketones and ketones to glucose.

After you eat, ketone blood levels drop while you process the new food (carbohydrates, fats, and proteins). Ketones start to increase 8 to 12 hours after beginning a fast.

When you eat every couple of hours, you never get to a point of fat burning.

You stop the important metabolic switching.

Fasting Your Way to a Healthier Brain

Metabolic switching also impacts the signaling pathways in your brain. The signaling pathways that are used during the glucose to ketone switch strengthen cell resistance to stressors.

This process also directly benefits the areas of your brain where cognition, mood regulation, and motor control take place.

On the surface it seems simple. Fasting helps you lose weight in the long term as well as control insulin levels and improve insulin sensitivity. It also improves brain function.

Even when you understand the benefits of fasting, it can still be confusing to know how long to fast, or how often. Experimenting with fasting in your own way is what’s important. When it fits your life well, you’ll stick with it.

Intermittent Fasting and When to Eat

Let’s consider two aspects: when you eat and how often.

Do you believe the key to weight loss is as simple as reducing calories eaten and increasing calories burned through exercise? Many people do think this!

Eating less and moving more isn’t enough if your goal is weight loss.

While that’s part of the equation, it’s not the whole story.

Timing when you eat can make a huge difference when it comes to eating for long-term weight loss.

Why is it important to consider timing? Because eating less and moving more fails to properly utilize your body’s natural energy stores.

You need to eat in rhythm with your circadian rhythm.

This rhythm is your body’s 24-hour sleep/wake cycle. Eating according to your circadian rhythm lets your hormones naturally play their part. During this 24-hour cycle, our bodies make and utilize different levels of hormones to match our activity needs.

Hormones and the Circadian Rhythm

Two hormones to consider are ghrelin and leptin.

Ghrelin tells you when you’re hungry. Leptin signals that you’re full and satisfied. Ghrelin levels are typically lowest at 8 a.m. and 8 p.m. Leptin levels rise as ghrelin falls. The release of leptin is generally followed by an increase in melatonin, the hormone that makes you drowsy.

If you think about these hormones and how they function optimally, the best time to eat your biggest meal of the day is between noon and 3 p.m., when your insulin is less likely to spike from food. In the evening, when your hormones are shifting into preparing for sleep, your melatonin increases and your insulin response becomes more sensitive.

So eating after 7:50 p.m. means a greater increase in insulin.

Because your body is winding down for bed, it’s not going to burn off the extra glucose. Instead, the glucose is stored as fat.

Here’s how this all works.

After you eat, glucose enters your bloodstream. In order to use that glucose at the cellular membrane level, your pancreas produces insulin. Insulin transports the glucose by unlocking the cell. Once inside the cell, that glucose is broken down and used as energy. Your pancreas will keep producing insulin until your blood glucose is all metabolized.

When the glucose is low (after eight to 12 hours of fasting), your body begins using energy from stored fat. Unlike glucose, you don’t need insulin to burn fat. Instead, your liver breaks fats down into ketones and releases them into your bloodstream.

This is essentially what happens during a fast. As I previously mentioned, this is called metabolic switching, and it can have a huge impact on:

  • Improving insulin resistance
  • Heart health
  • Neuroplasticity
  • Weight loss
  • Cell and organ repair

Here’s how to experiment with and experience the benefits of fasting when eating in rhythm with your hormones.

Begin implementing these three fasting principles into your eating habits:

  • Stop all food intake after 8 p.m. – water and caffeine-free tea are OK.
  • Breakfast only when hungry – except for morning beverage or water.
  • Eat the biggest meal of the day between noon and 3 p.m., followed by a lighter snack-sized dinner.

Keep track of your process and notice any changes in your mood, energy levels, or weight loss.

What is Intermittent Fasting, Is It Good for You, and How to Do It

Let’s now turn our attention to intermittent fasting.

Intermittent fasting involves switching between fasting and eating on a set schedule. During a fasting period you can choose to drink water, tea, coffee, or broth.

For those of you who aren’t familiar with this trend, intermittent fasting is a diet strategy in which you intentionally alternate a period of eating with a period of fasting.

You do this already when you sleep, but intermittent fasting tends to expand on your normal fasting window by making the fasting part of your day longer or by alternating days of fasting with days of eating.

Many people utilize fasting as a weight-loss tool. However, it has also been shown to improve brain function, reduce cardiovascular stress, promote self-healing, lower blood sugar, decrease inflammation, improve gut health, and make your metabolism more adaptable.

There are many myths about intermittent fasting, but let’s address the most common one.

The most prevalent myth is that all intermittent fasting is the same.

What is the Best Intermittent Fasting Plan?

There are many ways and suggestions for intermittent fasting.There are actually several types of intermittent fasting plans.

For example, time-restricted eating (TRE) patterns split your day between periods of eating and fasting.


The most popular form of TRE is referred to as 16:8. This means fasting for 16 hours and consuming all of your daily calories within an 8-hour eating window.

The 16:8 method is typically recommended about twice a week and needs to be built up to.

Other common TRE patterns use daily eating windows ranging from 12 hours down to one hour, a practice referred to as one meal a day (OMAD) fasting.

One Meal a Day

Eating just one meal a day sounds daunting, but this type of intermittent fasting is effective and safe. The OMAD plan is particularly useful in keeping your body in ketosis for an extended period of time, allowing for maximum fat burning.

Practicing this method once a week can produce some great results. More frequent OMAD fasting is not recommended because it can lead to headaches and fatigue.

The benefits of intermittent fasting for 23 hours with the OMAD plan include increased weight loss rates, a significant decrease in insulin levels, and better glucose oxidation.

Alternate Day Fasting

Multiple-day eating patterns that fall under the umbrella of intermittent fasting include alternate day fasting (ADF) schedules that split your week between periods of eating and fasting and extended fasting schedules that last for more than 24 hours.

As the name suggests, the eating pattern for an alternate-day fasting plan includes cycling between days of normal eating with a healthy diet and days where you restrict calories. This turns into one full day of fasting, followed by a day of feeding, etc.

Alternate-day fasting can produce some great results but is also strenuous on the body. Studies show drastic reductions in body mass index and weight, as well as lower blood pressure.


Many people use the popular “5:2” fasting diet, developed by Dr. Michael Mosley and detailed in his 2015 book, The FastLife. This involves eating a regular diet five days a week and then, on two non-consecutive days, cutting your calorie intake to about 25% of what you normally consume.

This is a simple type of easy alternate-day fasting that yields results. Because of this diet’s flexibility when scheduling, it can easily be worked into your week giving you consistent calorie restriction and weight loss.

In particular, the 5:2 method is good for heart health and preventing cardiovascular disease over the long term because it boosts cardiometabolic processes.

A simpler version of this is called the “dinner plan”. Finish your regular day with dinner, then don’t eat again until dinner the following day. That’s effectively a 24-hour fast. You can do this once, twice, or three times a week.

7 Health Benefits of Intermittent Fasting

As previously mentioned, there are many health benefits of intermittent fasting, even beyond the obvious one of weight loss.

Many who choose to use intermittent fasting find improvement in their overall well-being.

Losing Weight With Intermittent Fasting

Intermittent fasting is one of the better methods to safely lose weight and keep it off. It is certainly better than any crash diet that over time might damage your metabolism.

By burning the fat stores instead of glucose in the body, you can target the typical “problem areas” that many overweight people identify as fat stores, including the stomach, hips, thighs, and others.

Weight loss can ease pressure on your joints, help lower blood pressure, and increase your capacity for physical activity.

Slows Down the Aging Process

Studies have shown that the mitochondria in your cells decline with age, but when patients fasted for extended periods, these molecules were able to promote better cellular circulation to decrease the effects of aging on the body and increase your lifespan.

Reduces the Risk of Diabetes and Heart Disease

There is a favorable effect of intermittent fasting on heart health. Intermittent fasting lowers blood pressure and cholesterol. It also decreases stress in the body.

Additionally, with improved insulin sensitivity due to a fasting and eating pattern and low blood sugar levels due to reduced carbohydrate and sugar intake, diabetics and pre-diabetics can even reverse their insulin problems.

Benefits To Your Skin

Intermittent fasting can help clear up various skin conditions tied to hormonal imbalances. It also shows promising signs for skin cancer and inflammatory skin issues.

Improves Resistance to Oxidative Stress

During oxidative stress, there are imbalanced proportions of various hormones, free radicals, and antioxidants within your system. This leads to a variety of inflammatory issues.

Intermittent fasting actually helps to lower these internal stress levels by leveling hormone secretion. This is done because fasting reestablishes balance via autophagy.

Reduces Inflammation

Inflammation is a factor in many chronic diseases and health conditions including arthritis, cancer, and diabetes.

However, stopping inflammation and reversing the damage before it’s too late is entirely possible.

Studies show that fasting is able to prevent inflamed cells from circulating throughout the body, as well as boost the immune system’s response to further inflammation.

Improves Your Brain Health

Because of the cellular rejuvenation benefit of intermittent fasting, your body is able to purge toxins and waste from the entire system. This includes the brain.

Fasting is actually shown to have positive effects not only on mental health but also on cognitive ability and the risk or progression of degenerative neurological diseases.

Important Considerations Before Fasting

Fasting, when done properly, yields significant benefits that last for the long term. But because it’s so different from what most of us are used to, it’s easy to get some key details wrong.

The key to using intermittent fasting days and non-fasting days is consistency. Select  a fasting schedule and stick to it.

Don’t overeat when breaking your fast. You’ll undo all the benefits. It’s easier to plan a simple meal for when your fast is over.

Is Intermittent Fasting Safe?

Some people try intermittent fasting for weight management. Others use it to address chronic conditions such as irritable bowel syndrome, high cholesterol, or arthritis. But intermittent fasting isn’t for everyone.

Before you try intermittent fasting (or any diet) check with your primary care practitioner first.

If you’re on medication, consult a doctor before you start fasting.

Final Thoughts

Now that you know the science behind intermittent fasting and its potential benefits, you can make a more informed decision if you decide to try it. As mentioned, there are many styles and strategies used for intermittent fasting. Do your own research, experiment and see what works best for you, and draw your own conclusions. That’s always the best way to optimize your health!

If you feel stuck and need additional support to adopt a new healthy habit or routine, consider working with me. We can partner up in setting goals, drawing on your skills and strengths, and implementing strategies to help you find your way to lasting healthy success.

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For over 15 years, Shelli has been a freelance writer and wellness habit coach on Joyinmovement. She writes about brain fitness, creating a healthy lifestyle, traveling the world, and making positive habits stick. Stop procrastinating! Take action, join her free newsletter.

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