What is Intermittent Fasting & Who Should Do It?
Updated: Jun 7, 2022
What is intermittent fasting?
At this point this is a household term that I am sure most of, if not all of you, have heard. However, do you actually understand what it is and how it works? Intermittent fasting refers to a dieting style with set extended periods of minimal to no food consumption. It has been commonly referred to as a weight loss method. As a trainer I get questions about this type of eating everyday. Does it work? Is it sustainable? Who should do it and when?
Well, this is my attempt to explain the concept of intermittent fasting in hopes that you can better understand it and maybe even decide if it truly is something you may benefit from. Let me just clarify, I am in no way a registered dietitian or a doctor, and no two bodies are the same, so if you have specific questions about starting a new diet or what will work best for yourself you should consult a diet professional.
So, I will start by debriefing it this way: If your goal is to lose weight, there is absolutely no way to cheat the system. You simply need to end up in a calorie deficit at the end of the day. (For more info on this refer to my previous blog about weight loss here.) If by restricting the hours under which you allow yourself to eat you in turn restrict how many calories you are taking in, you are very likely to end up in a caloric deficit. This deficit is what contributes to your weight loss, but people naturally assume that the intermittent fasting caused the weight loss. Intermittent fasting can have a positive impact on many different body processes which can in turn help with weight loss, but it may also improve other body processes as well.
Various published research studies have concluded that intermittent fasting has a positive effect on metabolic regulation. An improvement in metabolic regulation can also assist in the following problems as well:
As you can see, the potential benefits of intermittent fasting go far past just weight loss. Before I explain how it can cause these benefits, let’s begin with exactly how the fasting process works. There are many different methods for fasting. I broke down a simple overview of some methods below.
5:2 Method - This method only involves fasting for two days a week, on these two days you limit your diet to 500 calories/day. The rest of the days of the week you maintain your normal and healthy diet. On the two fasting days people tend to eat one 200-calorie meal and a second 300-calorie meal. To maximize the health benefits of this method, you want to ensure these smaller meals are high in protein to fill you up. These two days can fall whenever in the week as long as there is a non-fasting day in between them.
16:8 Method (Time-Restricted Eating) - This method involves fasting for 16 hours, and allowing yourself to eat during the other 8 hours. A popular way to do so is by skipping breakfast to continue the fasting from while you were asleep. You can repeat this method as many days of the week as you would like. Be cognizant of the calories you intake during those 8 hours, as you are going to need that nutritional content to be able to carry you through 16 hours of fasting.
24-Hour Fasting: This method, as you could guess, includes completely fasting for 24 hours once or twice a week. Since this method requires longer times with limited nutrients, it is a bit more extreme and can come with harsher side effects like fatigue, hunger, lower energy, headaches, and irritability. A healthy and normal diet is recommended for the days you are not fasting.
Alternate-Day Fasting: This method involves fasting every other day. On the fasting days calorie intake is usually limited to about 25% of your normal intake. On non-fasting days you maintain your regular and healthy diet.
Now there are many pros and cons to every method and, as I mentioned before, no two bodies are the same. So your best friend may lose 6 pounds in one month by following the 5:2 method, but you only lose 2 and feel completely fatigued the whole time. My biggest advice is listen to your body. The human body is much smarter than we give it credit for.
So, let’s explain exactly how intermittent fasting can help with weight loss. I mentioned earlier that you have to be in a calorie deficit to lose fat. Specifically, you need to be in a 3500 calorie deficit every week to lose about a pound of fat a week. The whole point of fasting is that the time per day allowed for calorie consumption is limited; which inherently can eliminate snacking or eating extra unnecessary calories. Cutting out the extra eating will bring your overall calorie consumption down and decrease your net calorie balance, which could lead to a calorie deficit.
Intermittent fasting can also have benefits on metabolism, which plays a gigantic role in the way the body operates. This method of dieting tends to regulate the exact times you are eating at. An example of this would be eating every single day at 12pm sharp to break your fast, and having your last meal every day at 7pm before you begin your fast again. The time of day the body is digesting is one of the biggest factors that affects metabolic regulation. Metabolic regulation controls circadian rhythm, which is the natural 24-hour cycle the body operates on affecting all physical, mental, and behavioral changes. Circadian rhythm plays a large factor in hormonal secretion patterns, physical coordination, and sleep. So, improved metabolic regulation should improve hormonal balance, physical performance, and higher quality and effectiveness of sleep.
The body understands sleep vs wake times based on your energy consumption/eating patterns. Eating outside of the normal feeding phase can confuse the circadian rhythm of your body and offset your energy balance and metabolic function which will, as we just discussed, affect other body functions as well. So basically, eating on a more set schedule that incorporates fasting during the ‘night’ cycle of the body will automatically improve energy levels when awake, hormonal processes, digestive function, and more. All of these components work together to therefore improve their own respective functioning, which by improving their functioning can also make the process of fat loss that much more effective.
Improved metabolic regulation that comes from intermittent fasting also improves the gut microbiota. This is the microorganisms that live in the digestive tract and help control digestion and the immune system. Restricting the time under which the body is digesting food actually makes the gut microbiota more effective at energy absorption, energy expenditure, and energy storage - ultimately increasing energy levels of the body all around. If you struggle with any sort of indigestion, gluten insensitivity, IBS, or other digestive problems, intermittent fasting could help to align your circadian rhythm, and may help alleviate symptoms. In fact, the desynchronization of the circadian rhythm of different organs in the body can actually increase the risk of chronic disease like liver, fat, and skeletal muscle cancers. Therefore, realigning your circadian rhythm could also decrease the risk of chronic disease and alzhiemers.
As you can tell from these different points, intermittent fasting could have a positive impact on the body which could in turn help with fat loss, sleep, gut health, menopause, and more. However, it should be noted that any form of calorie restriction could have an alternative effect on the body. We all need a specific amount of calories a day to function properly and getting any less than that minimum amount can actually cause weight gain, fatigue, increased chance of injury, weakened immune system, etc. So, it is possible you may actually be under-eating and the best diet for you includes increased caloric intake. Some of the benefits from intermittent fasting may come from a more structured eating schedule. So, you may experience these benefits if you just stick to a more regimented eating pattern rather than fasting as well.
More research needs to be conducted on the different methods of intermittent fasting to conclude more specific benefits or disadvantages it may have. My goal here is to provide insight into what intermittent fasting is and why people have been seeing benefits from this method of dieting. This higher understanding should hopefully help you consider if this may be an effective method for you to look further into!