Intermittent Fasting: What is it All About Anyway?
By Dr. David Brady
Danielle Moyer
Intermittent fasting has been happening long before it got the name “intermittent fasting”. For centuries, groups of people all over the globe have abstained from food for durations of time for cultural and religious reasons. So, why has intermittent fasting blown up so much in the world of nutrition? What is it all about anyway?
There are two concepts behind intermittent fasting that you may not have heard of: Migrating Motor Complex and Autophagy.
To begin, there are different paradigms of intermittent fasting. Typically, “Time Restricted Feeding” is when an individual will restrict their food intake for a window of 8 to 10 hours or less every day during the week. Examples of this are skipping a meal or reduced meal frequency. On the other hand, there are longer periods of intermittent fasting around 16 to 48 hours with little to no energy (food) intake. This includes “alternate day fasting”, the 16/8 method (eating only within an 8-hour period), fasting two days per week, or periodic fasting periods lasting anywhere between 2 to even 21 days. All of these constitute intermittent energy restrictions.
Performing short-term frequent fasting, or “Time Restricted Feeding”, allows one to achieve a Migrating Motor Complex (MMC).
Imagine you want to clean your floors. If you are having a party, you are going to hold off on cleaning! There is no point when more mess is constantly coming in. But what about a calm Sunday morning when you are home alone? That is the same concept for MMC. Essentially, MMC is the act of your gastrointestinal tract contracting and “cleaning” your gut. It can only happen when the party’s over, or when you are not consuming any food. That is why MMC is called the “housekeeper” of the gut.
The duration of the entire MMC cycle length varies between individuals, but it ranges typically from 113 to 230 minutes (about 2 to 4 hours) of no food consumption. MMC allows us to empty our stomach and small intestine, and to send all remaining food into our large intestine to prepare for the next meal. When the body is unable to “clean” due to constant eating, this can leave our gastric content to stay for longer periods and potentially allow bacterial overgrowth or a variety of GI symptoms or occur. This has been correlated to small intestinal bacterial overgrowth (SIBO), as well as altered hunger signaling. Time restricted feeding encourages the full MMC cycle to complete.
The second element is induced by long-term fasting. It is called autophagy.
Autophagy literally translates to “eating of self” from the Greek meaning. Although that sounds alarming, autophagy is incredibly important for balancing our sources of energy, removing damaged cells, as well as eliminating potential pathogens. It is considered another “housekeeping” mechanism in our body. For that reason, autophagy has been associated in preventing diseases such as cancer, diabetes, autoimmune diseases, infections, liver disease, as well as neuroprotective effects in preventing diseases such as Alzheimer’s or Parkinson’s. In fact, autophagy is considered a promising target for cancer therapy, as it can play a role in inhibiting tumor growth.
The crucial element is that autophagy can only occur during states of starvation. It is an adaptive response of our cells and organisms during food-deprivation that promotes survival until energy is available again. However, this is not something that occurs in just 2 hours of no eating. It is difficult to assess exactly when autophagy is triggered, but one study found that it was significantly detected after 24 hours of food restriction. It was even more abundant after 48 hours of food restriction. Though that seems like a long time to go without eating, these periods allow cleansing throughout our entire body, including cleaning important organs, such as the heart and liver.
There are many other researched benefits of intermittent fasting. One, it is designed to prevent over-eating and increase your metabolic rate. This is associated with improvement in weight loss. Two, studies show it can improve cardiovascular effects, including improving insulin sensitivity and lipid profiles. Three, it has been shown to reduce oxidative stress and inflammation in the body.
Here are some guidelines on how to implement a fast:
1. Analyze your schedule and determine which common method would be right for you, realistically. Choice considerations can be dependent on frequency per week or during a specific time frame of the day. Do you work at a high-paced job in the morning where it is best that you have breakfast? Do you get off work at 7 PM and can eat dinner only after that time? These are things to consider.- Time-restricted feeding: An example of this is the 16/8 method, where you eat only within an 8-hour window. For example: 8 AM to 4 PM. The nice part about time-restricted feeding is it is the most flexible based upon your schedule.
- Whole day fasting: You can choose one to two days per week to do a complete fast, or choose to consume roughly 25% of your normal caloric intake. On the other days, you eat as you normally would.
- Alternate day fasting: On alternating days, you eat only one meal that provides about 25% of your normal caloric intake. For example, on Monday, Wednesday, Friday, you eat only one meal. On Tuesday, Thursday, Saturday, you would eat as you normally would.
2. Stay hydrated! A large percentage of our water intake on a daily basis comes from our food, so it is vital to drink water when you are not eating. This will lower the risk of fatigue, dry mouth, headaches, or thirst. Most people aim to drink 8.5 to 13 cups (2-3 liters) of water a day when fasting.
3. Find ways to entertain yourself that do not involve food. Eating is more than just consuming calories – people eat when they are bored, socializing, sad, angry, happy, etc. What can you do to stay calm and keep your mind engaged? You may be able to do a low-intensity exercise, such as walking or yoga, but be sure to ease into it at first.
4. During a fast, the feeling of “hunger” is expected. You may even feel tired or irritable. These are all normal! However, stop fasting if you ever feel unwell. If you feel faint, sick, nauseous, or concerned about your health, break your fast to nourish your body.
5. On your non-fasting days, do not “overeat” to compensate for the fasting days. Try to keep a normal diet inclusive of whole foods, lean protein, fiber, and fat.
Though there are many benefits to intermittent fasting, it is important to remember that these can be offset from the potential psychological impacts of intermittent fasting. Episodes of fasting can potentiate disordered eating or eating disorders, specifically binge eating disorders. It is also important to consider if you have a medical condition or need to eat based on medication use. Therefore, it is best to consult with a healthcare professional first.
If you are interested in intermittent fasting, there are many ways to do it safely and effectively. Like learning a new hobby, it is wise to start slowly and progress to more advanced levels. Just think, you already “fast” every night while you are asleep! There is a reason breakfast is called break-fast as it is.
References:
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Deloose E, Tack J. Redefining the functional roles of the gastrointestinal migrating motor complex and motilin in small bacterial overgrowth and hunger signaling. Am J Physiol Gastrointest Liver Physiol. 2016;310(4):G228-G233. doi:10.1152/ajpgi.00212.2015
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Glatigny M, Moriceau S, Rivagorda M, et al. Autophagy Is Required for Memory Formation and Reverses Age-Related Memory Decline. Current Biology. 2019;29(3):435-448.e8. doi:1016/j.cub.2018.12.021
Guelinckx I, Tavoularis G, König J, Morin C, Gharbi H, Gandy J. Contribution of Water from Food and Fluids to Total Water Intake: Analysis of a French and UK Population Surveys. Nutrients. 2016;8(10):630. Published 2016 Oct 14. doi:10.3390/nu8100630
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- Tags: diet intermittent fasting
- David Brady
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