Intermittent Fasting: Improve Energy, Lose Weight, and Reduce Your Risk of Chronic Diseases

Dr. Anne Zauderer

I spent the majority of my 20s in an insulin-resistant state. Sound hard to believe? Especially since I was a distance runner who ran an average of 6-8 miles per day, and 2 marathons per year? It’s true. I did everything “correctly,” according to conventional wisdom at the time. I was a vegetarian (technically a pescitarian because I ate fish), I ate low fat everything, and I made sure I got lots of whole grains. I did everything I could to stay healthy and yet I was miserable.

I was 10 pounds heavier than I am now, I had poor quality sleep, I was in a state of adrenal fatigue, I wasn’t having a menstrual cycle, I had constant anxiety and I was hungry all the time. At that point, I had no idea what was going on in my body. It seemed that the harder I “worked” and the more I worried about my health, the worse it got.

What I have learned over the years is that I have a strong family history of diabetes. This doesn’t mean that it is inevitable that I will develop diabetes, but what it does mean is that I am always going to have to work harder than some people to prevent it. My body doesn’t know how to utilize sugar efficiently as a long-term energy source. Current research is showing that I am not alone.


Before I can explain why intermittent fasting is such a great tool for long-term health, one has to understand how the body uses food for energy, otherwise known as metabolism.  Metabolism can be compared to the function of a car engine. You put fuel in and the engine burns it to make the car move. Our metabolism works the same way. However, what most people don’t realize is that we actually have two engines for burning fuel.

One engine burns sugar (or carbohydrates that get broken down into sugar molecules) and the other burns fat. This is a brilliant design because our ancestors had limited access to sugar. Their primary source of sugar was fruit, and it was only available during certain times of the year. Therefore, our ancestors’ diet was primarily made up of fat and protein.

The way our two engines work is that if you give the body sugar, it will burn that first because it gives us a quick source of energy. However, if you deprive the body of sugar, you will naturally shift over to burning fat. The advantage of burning fat is we store energy in our bodies in that form (as adipose tissue, or body fat). If we are using our fat-burning engine and run out of fat in our diet, we will naturally shift to burning stored fat without a significant drop in our blood sugar.

If we are primarily using our “sugar-burning” engine, when we run out of fuel our blood sugar will drop. When our blood sugar drops, we feel really hungry. It also causes us to be shaky, have foggy thinking, get irritable, and even triggers the release of cortisol, which is one of our stress hormones. Do you know anybody like that? Think about that person who gets “hangry” when they don’t have food (i.e. they are so hungry that they get angry!). What is happening is they are most likely eating a diet high in carbohydrates. As soon as their body has burned those carbohydrates with their “sugar-burning” engine, their blood sugar drops and they crave more. This leads to a pattern of not burning stored fat, always feeling hungry, overeating carbohydrates, and eventually adding more stored fat.  Long-term, all of this contributes to weight gain, low energy, elevated cholesterol (especially the bad type), insulin resistance and adrenal fatigue. Sound familiar?

Training your body to burn fat as fuel is like working out a muscle. Someone who doesn’t work out at all isn’t going to be able to go out and run 10 miles. You have to gradually build up your endurance. It is the same thing with your metabolism. If you have been a “carboholic” for the past 10 years, it’s going to take some time and effort to get you to the point of burning fat as a fuel. One tool to help you get there is fasting.


The idea of fasting dates back to our ancestors who were hunter-gatherers. With this lifestyle, food was not always readily available. Most of the time, eating came in a “feast or famine” sort of pattern. The biochemistry of our bodies adapted to that way of living. When you abstain from food for a period, it creates a biological stressor to the body. This hormetic effect induces pathways in the body that can have healing effects.

Health Benefits of Fasting1:

1.       Blood sugar stabilizes
2.       Insulin levels lower and insulin resistance is improved
3.       The gut and immune system get a chance to rest
4.       Ketones are produced
5.       Metabolic rate increases
6.       Damaged cells are cleared out
7.       Hunger lessens
8.       Excess body fat is shed
9.       Levels of the hormone insulin-like growth factor 1 (IGF-1) are reduced (associated with many cancers such as breast and prostate cancers)
10.   The rate of aging slows
11.   Bat burning is boosted
12.   Brain function is protected

In our modern world, we have a negative perception around skipping meals. Very often, we associate skipping meals with a sharp decrease in blood sugar, decrease in focus and an increase in irritability. We’ve been taught that breakfast is the most important meal of the day! Unfortunately, those touting that outdated axiom are also the ones pushing sugar-filled breakfast cereals, pop tarts and pastries as respectable breakfast choices. We also snack more than we ever did in the past. Compared to 30 years ago, we daily eat around 180 calories more in snacks and beverages (including milky drinks, smoothies, carbonated beverages). We also eat an average of 120 calories more during our regular meals2. Over time, this can add up and contribute to the soaring rates of obesity we are seeing in our country.

How to Fast

There is a substantial amount of research that supports the idea that the less you eat over time, the longer you will live. However, severe calorie-restrictive diets are difficult and therefore compliance can be low. According to Dr. Joseph Mercola, “Instead of regulating how much food you eat, as with long-term calorie restriction, you only need to modify when you eat – and of course wisely choose the foods you do eat.” One way to do this is called intermittent fasting.

Intermittent fasting* is restricting your eating each day to a 6- to 11-hour period. As a result of this, you will be abstaining from food for 13 to 18 hours each day you are on the fast. This means you are not severely restricting the number of calories you eat, but rather the time frame in which you eat them. For example, under this plan if your last meal was finished at 7:00pm, you would not eat until around noon the next day. This would give your body a 17-hour window of fasting. This is enough time to acquire the benefits outlined above (see text box entitled “Health Benefits of Fasting”).

As I mentioned, you will have to train your body to burn fat as your primary fuel source of energy. It can take up to 2 months for your body to adapt to this way of eating. The first step, even before you begin experimenting with fasting, is to cut the excess carbohydrates from your diet, especially those consumed at breakfast and lunch. The body is naturally more insulin-sensitive after 3:00pm. Therefore, if you are going to have good, complex carbohydrates (such as root vegetables, fruits, quinoa, and grains such as rice) the best time to have them is later in the day. Try to limit breakfast and lunch to foods that are high in good fats, protein, and fiber (such as green, leafy vegetables and cruciferous vegetables). What you will notice with this pattern of eating is that you will be less hungry in between meals and have more energy.

After your blood sugar is more stable and excess carbohydrates are removed from your diet, that is a good time to try intermittent fasting. The first step is to stop eating 3 hours before bedtime. This will allow your body to use the time you are asleep to detox and repair, rather than digesting food you have eaten.

Once you are comfortable with a 3-hour fast before bedtime, try pushing back when you eat breakfast. If your normal breakfast is at 8:00am, try eating it at 9:00am. As you gradually ease into longer fasting periods, you might find yourself hungry. Work through the hunger and it will pass.  Over time you will find yourself being less and less hungry. Eventually you will notice an overall stabilization of your blood sugar and the effects of the fast will be felt all day long.

One critical point to note is that the meal you use to break your fast is one of the most important aspects of fasting. If you choose to go 18 hours without food, but you break the fast by gorging on a fast food hamburger meal with a soda, you will have completely negated any positive benefits of fasting (in fact, you might even be making things worse!). Make sure you are ending your fast with a whole foods meal that has a lot of good fats, protein, and vegetables.

Intermittent fasting is one tool that might be helpful for you. As with any new program, listen to your body first and foremost. If you are not able to adapt to this type of eating, perhaps this might not be the best program for you. Or you might need to start under the guidance of someone who can help you through it. For many, though, fasting can be a powerful tool in their quest for maintaining a healthy weight and lifestyle.




*Beginning a fasting program like this is best done under the care of a physician. Some of the contraindications for going on a fast are: uncontrolled blood sugar (diabetes), pregnant women or women who are nursing, people who have serious adrenal issues, and use of certain medications (consult your doctor). Please consult your physician before beginning a program like this.

  1. Mercola, J. (2017) Fat for Fuel. Carlsbad, California: Hay House Inc.
  2. M. Popkin and K.J. Duffey. “Does hunger and satiety drive eating anymore? Increasing eating occasions and decreasing time between eating occasions in the United States.” American Journal of Clinical Nutrition, 91. (May 2010): 1342-47