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The Benefits of Intermittent And Prolonged Fasting

3 years, 2 months ago

14801  0
Posted on Sep 22, 2020, 2 p.m.

The following article was written by Christine Bishara, MD who is the A4M member of the month, she practices preventive and personalized patient care, and believes in a proactive approach to healthcare. 

Intermittent fasting has become the #1 dieting method and there’s a valid reason. As someone who has done intermittent fasting for over 30 years, I have found it to be the most effective method of weight management. 

As an obese teen, my impetus for change came the summer of my sophomore year of high school. My mom, sister and I had gone on a cruise to Bermuda. As is the protocol on these ships, the Captain’s Dance Night was one of the highlighted events. Just as the dance was starting, a stranger approached both my mom and older sister to dance, but they politely declined. He took a look at me and walked away. A few weeks later, I had my annual pediatrician appointment, which involved the dreaded “getting on a scale.” My pediatrician did not mince words. I still remember the exact words she said, as she told me I was sixty pounds overweight. I distinctly also remember  her saying “ you will never be able to lose all this weight.” Those were harsh words to hear as a 15-year-old. I am not sure why she said that to me, but in hindsight, maybe she knew me better than I knew myself. That summer, I set out to prove her wrong. 

Initially, my plan involved consuming 1,000-1,200 calories daily. I often found myself hungry, so I started experimenting with eating more. I increased my caloric intake to approximately 1400-1600 per day, but started ending my meals earlier than usual and waiting as long as I could the next day before eating breakfast. Intermittent fasting was not even a thing back then, and in all reality, I was just trying to find a way to eat a little more and still lose weight. I soon discovered that my plan was working. That summer I lost 30 pounds. 

It wasn't until I studied Biochemistry in medical school that I discovered why intermittent fasting is such an effective mechanism for weight loss and maintenance. Eventually, I managed to lose 70 pounds by the time I graduated and have kept my weight stable since then. We now know that there are many benefits to fasting and I believe it’s what has helped me stay relatively healthy with no medical problems.

I’d love to share the reasons why it’s a great option for maintaining overall health. To do that, we will first need to understand the science behind it.

Autophagy: The word autophagy in Greek literally means “eating oneself” and this is exactly what happens when we fast. Think of autophagy as the low battery mode setting on your phone. Our bodies are constantly in survival mode, always trying to ensure that we have enough fuel for our cells to function. Autophagy works to protect us for as long as possible in case we encounter times when we don't have access to food. When in a fasting state, your body must reserve energy for its most vital functions, so it kicks into “cleaning house” mode. This means that any unnecessary components of our cells are lysed, or removed. Apoptosis-programmed cell death, also helps to save energy for the body’s most vital functions. Apoptosis and Autophagy are accelerated when we sleep and autophagy is initiated by fasting. Autophagy usually kicks in after 16-20 hours of fasting. The longer your body is in autophagy, the better. Since autophagy stimulates the death of certain cells or parts of cells, it can also program the death of dysregulated and dysfunctional cells that have gone haywire or have become prone to developing cancer.

Now let's discuss the types of fasting that allow us to benefit most from autophagy. There are two types of fasting - intermittent and prolonged. 

Intermittent Fasting:

This is a loose term as there are several different methods. I’ll focus on the three most effective ones:


This is my personal favorite. Time-restricted fasting and I have a long history together, so maybe I’m a little biased in my love for it. This is also probably the most common method of intermittent fasting. It involves restricting the time of eating to a 6-8 hour window. I recommend that if you have not done this before, to start with twelve hours first. Although intermittent fasting is generally considered safe, there are some medical conditions where fasting is not recommended, and it’s always best to get the all-clear from your doctor before starting.  

During the time-restricted fast, I recommend eating two meals and a snack, or- just two meals. Everyone is different, but I believe unless one is underweight, most people do not need to eat three square meals a day. You also want your meals to be at least 60-70% plant-based. Once you've mastered twelve hours, move on to fourteen, then sixteen hours and finally eighteen hours of caloric restriction. Ideally, you do not want to eat four hours before you sleep since the best time for autophagy to kick in is during that time.

5:2 day fast:  

This fast consists of two days of fasting where you don't eat from 24 hours the day prior, For example, If your last meal was 7 pm the night before, you can fast till 7pm the next day and then eat a 500 calorie meal. The two days do not have to be consecutive, although it’s more effective when they are. During the 5 days of normal eating, the average person should not consume more than 2,100 calories, but this varies based on sex, weight and muscle mass.

Alternate day fast: 

This is similar to the 5:2 day fast but, you're alternating normal calorie days with 3-4 fasting days of 500 calories. This is good in that it gives the sense of not being deprived of food on a regular basis.

Although the alternate day and 5:2 day fasts are a little more rigid, they are also beneficial since the longer a fast, the better the health results, especially when it comes to autophagy which is potentiated with longer fasts.

Prolonged fasting:

This is defined as fasting of longer than 2 consecutive days. The most common of these is a 3-5 day water fast, however, I do not recommend prolonged water fasts except under extreme circumstances and closely monitored by a physician. Risks are involved with long term water fasts, not to mention that they're also almost impossible to stick to. Last year, I was introduced to a safer and more effective method. I am not big on promoting anything, but I do believe in the science behind this particular diet called the Fasting Mimicking Diet (FMD) by Prolon. The goal of the FMD is to mimic a 5-day water fast, but while eating food. The benefits of prolonged fasts are sustained autophagy, weight loss and cell rejuvenation.  The diet has been studied extensively and has been patented and proven to initiate cell renewal.

Now that we’ve explored how to fast and why it’s beneficial, let's discuss what happens to initiate this cascade of potentially life long health benefits.

Glycogenolysis and Gluconeogenesis

We have all experienced hunger sensations. Again, this is our body’s survival mode kicking in to make sure it receives adequate glucose for all its cells, at ALL times.  Hunger is a good sensation. It is what prevents us from starving to death when we don’t have food in front of us to remind us to eat. What makes it problematic is when that sensation occurs more frequently than we’d like.  We have all experienced that hunger feeling that hits late in the evening after we have eaten dinner and eventually entices us towards the pantry or fridge for a late-night snack.

Understanding the reason behind the cravings makes us better equipped to resist them.

So why does that hunger feeling kick in? Blame it on Insulin, the hormone responsible for facilitating glucose transport into our cells. Insulin needs to do its job, so when your body runs out of carbohydrates consumed from food, it knows it has to alert you to bring in more fuel. Here's the trick though-Insulin didn’t get the memo that our bodies have a backup plan. Enter Insulin’s arch-enemy, the hormone, Glucagon. When insulin is up, Glucagon is down and vice versa. Although they are opposites, they're both essentially fighting for the body’s survival, but through different means. The role of Insulin and Glucagon is to ensure that cells receive fuel at all times. So, when insulin drops, it stimulates the hunger pathway urging you to eat. What happens when you ignore that urge? The levels drop and in comes Glucagon. Glucagon’s job is to get fuel to the cells when we don’t eat. It does this in two ways:


Your liver has a stored supply of glycogen (roughly 1200 calories worth) which can be converted to glucose for cells. The body starts to utilize glycogen stores after about 8-10 hours of fasting. When Insulin levels decrease and hunger signals are ignored, Glucagon alerts your liver to start using stored glycogen for fuel, hence the word LYSIS, meaning to "break down." This is why when you go to bed hungry, you don't usually wake up hungry since your body has utilized other means to feed its cells.


Additionally, our bodies are able to make glucose for cells by activating a mechanism called Gluconeogenesis. The word genesis here means "to create" and in this case, the body creates glucose. In order to do this, the body resorts to fat burning for fuel and we enter into a state of ketosis. 

These mechanisms have many health benefits including stabilization of blood glucose levels and prevention of insulin resistance, a condition caused by consistent stimulation of Insulin release throughout the day.

Here are my tips on how to start your fasting journey:

1- Find a doctor who can effectively rule out any contraindications to fasting. It’s good to have bloodwork taken to monitor progress.

2- Pick a type of intermittent fasting and resolve to do it 80% of the time. You can experiment with the different types to see what works best for you.

3- At least two to three times a year, consider doing a prolonged fasting-mimicking diet to get all the benefits of cell renewal through autophagy.

I hope this helps. Cheers till next time.

Author Bio:

Christine Bishara, MD is the founder of From Within Medical, a medical wellness practice that places emphasis on the mind-body and gut-brain axis to prevent and manage disease. With over 20 years of clinical experience, time and time again, Dr. Bishara has discovered that the connection between these systems plays a significant role in disease prevention and management, but it has not been adequately addressed. Dr. Bishara is Board certified in Internal Medicine by the National Board of Physicians and Surgeons and is certified in Integrative Medical Weight Loss by the American Academy of Anti-Aging Medicine. She has previously served as Assistant Professor and Clinical Preceptor at New York Medical College. Her professional experience has spanned academically and clinically in both inpatient and outpatient settings.

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