I frequently receive questions from people asking how intermittent fasting works.  There is a lot of buzz around the subject but most people are unsure about the specifics.  What is intermittent fasting?  How does it sustainable?   Is it even safe?

Chances are you grew up in a household where you were told the Breakfast is the “most important meal of the day.”  It was supposed to give you the energy you needed to do well at school and later at work.  It was also supposed to spike your metabolism.  If that’s the case, then what’s with the popularity of intermittent fasting?

Isn’t skipping breakfast a bad thing?

The reality is that as new studies come out, we are learning more and more about how the body truly works.  And it’s not that your mom was wrong all those years ago.  It’s just that she was working off old information (remember, the world was flat before it was round).

The truth is that Danielle and I have tons of online clients we have helped, and intermittent fasting is just one tool in our belt that works for a lot of people.

It might be just what you need.

Intermittent Fasting 101

Let me start by first telling you that Intermittent Fasting (IF) is NOT a diet plan.

Intermittent Fasting is an eating plan.

Intermittent fasting is a decision to limit the times of the day when you are eating and the times of the day when you are fasting (not eating).  It’s pretty simple.

Today we can go to our kitchens at eat whenever we want.  We can even order food and have it delivered to our doorstep with the click of an app.  But it wasn’t always this way.  It wasn’t until the past century that we’ve had round the clock access to food.

How Our Ancestors Lived

If you think back to how our ancestors lived, food wasn’t reliably available.  They were hunters and gathers who had to find (and sometimes kill) their food.  There were long stretches of time when their bodies were in a state of fasting.  It wasn’t a choice.  It was reality.

So, our bodies have evolved over generations to be very efficient at storing energy in the form of glycogen and fat just in case we have to go days (or even weeks) without much to eat.

Without having to go back to living like the Flintstones, we can bring back an eating plan more inline with how our bodies have evolved.

There are a few variations when it comes to Intermittent Fasting, but they all are along the lines of limiting eating during specific time periods.

The Intermittent Fasting 16/8 Plan

When people asking “how intermittent fasting works” they are most often talking about the 16/8 fasting plan.  This is the most common plan I have seen people follow when they switch to IF.  It’s also the least restrictive.  Basically, you limit your eating window to an 8-hour period of the day and fast the other 16 hours.  There doesn’t have to be a calorie (or food) restriction to follow this plan.  You may be still eating the same types and quantities of food as before.  You are just doing it within a specific window of time.

For example, at my school lunch begins at 11:45 am.  Skipping breakfast and an am snack, I eat my first meal of the day just before noon and I finish my last meal of the day by 8pm.

Does it matter which 8 hours of the day you eat?

No, over time it’s much more important to be consistent with your schedule.  If you want to eat at 6am and be done at 2pm that works.  Another common schedule we see teachers follow is to have their first meal at nutrition break (around 10am) and their last meal by 6pm.

You know your schedule better than me, so I would recommend a plan that fits your life versus trying to make life fit your eating plan.

The Intermittent Fasting 18/6 and 20/4 Plans

These are more restrictive variations of the 16/8 IF plan.  By shortening the eating window and fasting for longer periods of time, your body has having to make more adaptions.  I will go into more detail below on the science behind IF.  But for now, just know that the longer your body goes without food, the longer it must use the energy reserves (stored carbohydrates and fats) currently available to keep you going.

Because these are more restrictive plans, I recommend people start with the 16/8 and see how their body responds.

You might be so busy during the fasting period of the day that you don’t even know you skipped a meal.  Or you may want to eat your own hand.  It all depends.

But if going until noon before eating is a stretch of your willpower, I wouldn’t go beyond this at first.  Remember, consistency is the “secret sauce” to amazing results.

The OMAD Plan

OMAD is short for One Meal A Day.

And you guessed it.  You are limiting yourself to a single meal during a 24-hour time period.

Personally, I have never tried OMAD.  But that doesn’t mean it’s not a good plan.  My friend James (who is the IT guy at our school) has been doing OMAD for months now and it works great for him.  He is always busy putting out fires at work so there is seldom time for him to sit down and eat, even if he wanted.  After school he works out.  And then his meal doubles as a post workout feast.

Unless you are going to an all-you-can-eat buffet, OMAD goes hand in hand with reducing your daily calorie intake.  Especially if you are eating nutrient-dense whole foods.

The potential downside is that you could be spending more time each day thinking about food than eating it.  Which isn’t a healthy or sustainable lifestyle.  I know I’m a broken record on this.  But consistency is key.

The 24-Hour Intermittent Fasting Plan

For some people, completing a 24-hour fast once a week is a great way to reset the body while limiting your calorie intake.

If you finished dinner at 8pm you would go until the following day at 8pm to have your next meal.  If you currently eat 3 meals a day, you would skip breakfast and lunch during your fast.

One note of caution is that I don’t recommend people experiment with an extended fasting for 24 hours on days they are exercising.  It works great for rest day.  But trying to finish a crazy leg workout when you haven’t eating since last night’s dinner is a recipe for disaster.

Why Do We Gain Weight In The First Place

Before going into the details of Intermittent fasting, let’s do a quick review of obesity and what causes someone to gain weight.

Obesity can be defined as the “hormonal dysfunction of fat accumulation.”  We know that calories are the proximate cause of obesity, but obesity is a hormonal imbalance.  Not a caloric imbalance.

Don’t believe me?

This flies into most of the conventional wisdom that predicting weight gain or weight loss is as simple as counting “calories in” and “calories out.”  The problem is that caloric intake and expenditure are dependent of one another.  Decreasing the number or calories consumed triggers a decrease in the number of calories used.  And the end result is that while there may be some weight loss early on, the end result is very minimal weight loss over an extended period of time.

But aren’t all calories the same?

No.  Different foods will evoke different metabolic and hormonal responses.  And different foods are not likely to have an equal effect on weight gain.  Proteins, fats, and carbohydrates all provide caloric energy for the body, but are processed differently.  The result is different hormonal stimulation and release in the body.

Insulin And Obesity


We know that insulin causes obesity.  Numerous studies have concluded that insulin causes weight gain.  And the more insulin you have flowing through your bloodstream, the more obese you get.  Because high insulin levels cause weight gain, the foods you chose to eat become increasingly important if you goal is to lose weight.

So can’t I just eat foods that don’t cause a rise in insulin to lose weight?

Yes and no.  Food selection is very important.  Eating 1600 calories of a nutrient dense, whole food diet will lower your insulin levels compared to eating 1600 of Swedish Fish.  But simply lowering your insulin level through your food choices doesn’t solve the second hormonal factor that causes weight gain.

We must also solve the problem of insulin resistance.

What is Insulin Resistance

The body will begin to resist anything that it experiences in high levels for a prolonged period.  Antibiotic resistance is a perfect example of this.  Doctors know that the prolonged use of antibiotics declines in effectiveness over time.  When the body experiences a consistently high level of insulin the receptors on our cells begin to lock glucose out causing its levels to rise in the blood stream.  High blood glucose levels signal the body to release even more insulin.  Pretty soon we have a vicious cycle forming where the body protects itself by becoming resistant to insulin while the resistance itself promotes high insulin levels.

High Insulin levels causes insulin resistance.

And the longer this cycle continues, the worse it gets.  Therefore, the longer you are obese, the harder it is to lose the weight.  The longer people are stuck in the cycle of insulin resistance, the harder the cycle is to break.  Insulin resistance leads to high insulin levels, regardless of a person’s diet.  So even if you change what you eat, your insulin resistance would keep your insulin levels high.  Simply changing your diet might not lead to weight loss.

To solve both the problem of high insulin levels and insulin resistance we need to focus on three factors: what you eat, how much you eat, and when you eat.

Intermittent Fasting Benefits

The connection to Intermittent Fasting lies in the fact that insulin resistance requires the body to have consistently high insulin levels.  It’s not just what you eat or how much you eat.  But also, when you eat.

If you were to have breakfast at 6am, lunch at noon, and dinner at 6pm, your body would have 12 hours of feeding where insulin levels would be higher and 12 hours of fasting where insulin levels would be lower.  In addition, during the 6-hour gaps between meals your insulin levels would dip. Unfortunately, this is not the norm anymore.

Today we eat more frequently and have a longer feeding window compared to just a few decades ago.  And the result is that our insulin levels aren’t just high because of what we eat (added sugars, processed carbohydrates, and chemical sweeteners, etc.) but how often we eat within a 24-hour period.

Interrupting The Insulin Resistance Cycle

To lose weight we must interrupt the insulin resistance cycle we have fallen into.  And to break the cycle we must have periods in our day with very low insulin levels.  This is how intermittent fasting works to break the cycle of insulin resistance.  Since all foods will promote the release some insulin, the only way to guarantee we lower our insulin levels is to have our body in a state of fasting for an extended period.

Since Yoshinori Ohsumi won the 2016 Nobel Prize for his work understanding how cells recycle their content through the biological process of autophagy, there have been several studies explaining the connections between fasting, autophagy, and weight loss.   We are still learning how the processes work, but we do have significant evidence to say that when the body is not focusing on digesting food it can reset how the cells work.  And this includes the sensitivity to insulin.

In a nutshell, this explains why Intermittent Fasting works.  By breaking up the time you are eating with prolonged periods of fasting, you are giving your body a chance to break the cycle of insulin resistance while using the calories already consumed to power the body.

Is Intermittent Fasting Sustainable

When sharing this weight loss strategy with others the first concern I hear this the fear of being “Hangry.”  If you aren’t familiar with the term, it refers to not eating for a prolonged amount of time will lead to feeling irritable and frustrated.

If you are switching to IF from a lifestyle where you ate within an hour or so of waking up and then ate every 2-3 hours until you went to bed, then there will be some getting used to.  But generally, the reality isn’t nearly as bad as the anticipation.

I would recommend starting this plan when you are busy because I think that’s one of its key benefits.  You don’t have to worry about what you are eating every few hours.  And this frees up more time in your day to take care of work, exercise, relax with friends, and even rest.

Knowing how intermittent fasting works with my body, I start my morning with a cup of black coffee and I am ready to conquer the day.  I can workout in the am or focus on work that is at the top of my priority list with amazing focus and intensity.

Can I Exercise While Fasting?

Aside from the issue of hunger pains, this is the second most common question I get.  And my answer is usually, “it depends.”  If your body is sensitive to insulin than your workouts will be fine.  Your body will convert its reserves to fuel keeping your blood sugar level stable.  You may even find your workouts improve as you don’t feel sluggish exercising after you eat.

If you are experiencing insulin resistance, then I would stick to cardio while fasting and do your resistance training 2-3 hours after eating.   If you aren’t sure, send me a message or talk with a certified fitness professional and they and give you more individualized recommendations.

I have been following IF for years now, but I still split up my workout routines when I am following a program with heavy resistance (sets with 8 or less reps) training.  Like most things, I would experiment and see how your body responds.

Getting Started With Intermittent Fasting

Everyone may have slightly different results with IF.  The only way to know how intermittent fasting works with your body is to pick a plan and track your results (NOTE: you should always check with a doctor before trying this or any other eating plan).  You will definitely want to keep a food log and journal to determine how IF affects your results.  Mood, energy level, and body composition changes are going to be slightly unique to each person.  We just need to figure out what’s the best plan for you.

There are multiple ways to follow Intermittent Fasting.

  1. You can follow a 16/8, 20/4, or OMAD plan as detailed above. As I mentioned, I recommend people start at 16/8 and then gradually shirk the feeding window based on how your body responds.
  2. You can follow the 24-hour fasting plan. Again, I would plan when you will be skipping meals based around what works best for your daily life.
  3. You can be ‘flexible” and skip a meal here or there without following a specific plan. This falls more in line with calorie reduction so long as you don’t compensate by having double meals later in the day.  There are days I don’t get home until 8 or 9 so skipping dinner and going directly to bed becomes my default plan as opposed to eating right before I go to sleep.

It’s time to get stated.

Excessive planning can be a form of procrastination.  Too many people spend valuable time planning and NEVER act.  Don’t let this be you.

Begin by determining your starting weight and take your “before photos.”

Then track your progress over the next 4-8 weeks to using your food tracker and your journal.

Finally, evaluate your results to figure out if IF works for you and if it’s something you want to continue doing.

Final Thoughts

If you’ve read through this article and still aren’t sure how intermittent fasting works, it might be worth investing in some professional help.  We can help make sense of everything for you and guide you STEP BY STEP through the process of incorporating Intermittent Fasting into your life.

We have a few options to help you out.

  1. Our 1-on-1 Online coaching program will give you the support and accountability you need to get results. We are certified nutrition and fitness experts (who happen to also be public school teachers) and we understand the demands of the teaching profession.  Best of all, we offer a 100% MONEY BACK GUARANTEE for everyone who chooses to work with us.
  2. Join our Online Fitness Community where we offer education and inspiration on all thing’s health and fitness.
  3. Subscribe to the Fit Teacher Network Newsletter. I offer tips, recipes, and answer frequently asked questions pertaining to both fitness and my crazy busy life as a teacher, husband and dad.