Intermittent Fasting: What's the big deal?
If you read the news at all, or check much of any social media you will likely have seen something about intermittent fasting.
Why is it all the rage? What is the point? More importantly, does it work?
I plan on answering all of this and more in this blog post, making the benefits and dangerous of fasting easy to understand, after which you can make your own judgement on it. Let’s begin with defining what the term even means in the first place.
“Intermittent fasting (IF) is a term used to describe a variety of eating patterns in which no or few calories are consumed for time periods that can range from 12 hours to several days, on a recurring basis. - It can also be referred to as time restricted feeding (TRF).”
If you ask me, it can be a bit of a silly name because we really fast every single day. Whenever your head hits the pillow you are “fasting” and you do so until you wake up and subsequently decide to eat. Popular media likes to give special names to things to make them trendy, that way we all think it is the NEXT BIG THING and then everyone wants to try it, just like the OMAD diet which is the One Meal A Day diet… once it has a name, it must work right? Wrong. Hardly ever the case. Most often, health is something acquired over a series of habits done on a consistent basis with constant evaluation and adjustment to gain continued results. It is hard to shove health in a small box or hide it under ONE DIET protocol. Back to IF, (I will refer to intermittent fasting or fasting in general, as IF for the rest of this blog) let’s start by listing out all the reasons most people decide to try it.
Lose weight (probably the most common)
Restore their gut
Lower inflammation
Reduce oxidation and free radical build up in the body
Have a black and white picture of what they can and cannot do for their “diet”
Regulate blood sugar
Reduce brain fog, drowsiness and overall fatigue
Regulate their circadian rhythm (to sleep better)
All of the reasons listed above are amazing reasons to fast, but can you believe there are even MORE than these? Fasting reaches far beyond aesthetics and really is something to consider if you want to increase the longevity of your life and improve your overall health. This is one of the main reasons I have begun to implement fasting into my monthly routine.
We all know that caloric restriction (without malnutrition) helps us lose weight and extend our life span. Many studies of 6-month caloric restriction improved cardiovascular risk factors, insulin sensitivity (ability to breakdown, store and utilize carbohydrate with ease) and mitochondrial function (this one is the most important and will be described later). IF is a version of caloric restriction, but is fundamentally different by the focus of alternating the amount of food someone consumes from day to day and basing meals around particular time periods. Straight caloric restriction simply lowers calories for X amount of time. IF alternates eating patterns to have lower food during a certain time period one day and more normal food the next but perhaps still during a certain time period.
Fasting from an Evolutionary Standpoint
As human beings we evolved experiencing extended periods of little to no food. We had a continuous cycle: we hunted, killed, ate, and hunted again with an occasional gathering of available fruits, nuts, seeds or vegetables along the way. This was all dependent upon the season and what was naturally occurring at that time. (obviously this all changed during the advent of fire and farming, but that is another topic) Take humans out of the equation and look at wild animals, how do they eat? Are they getting food every 4 hours, and timing their post workout meals to optimize their “gains”, uhhh NOPE. They adapt, their metabolism shifts and those that function optimally while “fasted” survive, make the next kill and lead the way. Likely, our most metabolically adaptable ancestors outlived the others and paved the way with their optimal cognitive and physical abilities.
Historically fasting has been used for religious reasons and was evenly widely accepted by those such as Benjamin Franklin and Mark Twain, heck it was used to treat Type 1 and 2 diabetes back in 1914 (3). My point? It is nothing new and has been around for a very, very, very long time with much-proven success.
Here are some typical fasting options:
Intermittent Fasting (IF)This eating pattern involves fasting for varying periods of time, typically for 12 hours or longer.
Calorie Restriction (CR)This eating pattern involves a continuous reduction in caloric intake without malnutrition.
Time Restricted Feeding (TRF)This eating pattern involves restricting food intake to specific time periods of the day, typically between an 8 – 12 hours each day
Alternate Day Fasting (ADF)This eating pattern involves consuming no calories on fasting days and alternating fasting days with a day of unrestricted food intake or “feast” day.
Alternate Day Modified Fasting (ADMF)This eating pattern involves consuming less than 25% of baseline energy needs on “fasting” days, alternated with a day of unrestricted food intake or “feast” day.
Periodic Fasting (PF)This eating pattern consists of fasting only 1 or 2 days/week and consuming food ad libitum on 5 to 6 days per week.
Now, I am going to take some time here to dig into some science, if you want the science keep reading and click on the header to find the research article that my information comes from, if you DO NOT, then skip ahead in each section and just read the bolded text, where I summarize the important stuff.
Fasting Flips Your Metabolic Switch
Traditionally our body runs, moves and operates primarily from carbohydrates, they are the preferred method of energy for us, but our body is adaptable. Carbohydrates are easily absorbed and quickly broken down into simpler components like glucose, when this glucose is linked together it becomes long chains of gycogen which fills our “glycogen stores” within our muscle cells and our liver (a large source of glycogen = energy). Glycogen can quickly and easily be broken down into readily available glucose for energy. But what happens if we are not eating, what happens if we do not eat for 18, 20, or 36 hours? Our body uses up our stored glycogen which can be up to 500g (This is over 2,000 cal of energy) and needs to switch to a new source for energy.
FAT.
We prefer glucose but our body is smart, it adapts! And we shift to fat utilization. Specifically, we begin to mobilize fat through fatty acids and fatty acid-derived ketones. This only occurs once the glycogen stores in the liver are completely depleted, when this happens our body turns on the switch to burn adipose tissue… FAT… therefore creating fatty acids. This typically happens anywhere from 12-36 hours after the stopping of eating (I would push closer to 36 as 12 hours is not that long to go without eating but everyone is different). These fatty acids are then metabolized through beta oxidation and Wa-La we have the infamous “ketones” (ever heard of the keto diet?, yeah well, that is low carb, so what happens? no glucose, no glycogen, body switches over to fat stores and creates KETOnes for fuel).
So great, the switch is flipped, why does this matter?
These ketones head to our muscle cells and neurons to create energy and PRESERVE muscle and brain function during fasting. This “switch” also induces mitochondrial production (more on this to come, sit tight). So overall this switch helps the body get energy from lipolysis (eaten fats broken down), adipose (fat cell breakdown), and ketones. All of this help preserve muscle mass, if this did not happen the body would feed on itself and breakdown your muscle for energy, that is bad, and therefore the body uses the above process instead. In fact, IF protocols retain MORE muscle mass following the protocol when compared to normal calorie restriction protocols (1, 2). This switch seems to produce long-term increases in muscle growth and endurance capacity, therefore, improving body composition in overweight individuals.
Are there dangers in fasting?
Most good things in life come with some discomfort or potential costs. Fasting is no different. These include: nausea and vomiting, edema, alopecia and motor neuropathy, hyperuricemia and urate nephropathy, irregular menses, abnormal liver function tests and decreased bone density, thiamine deficiency and Wernicke’s encephalopathy, and mild metabolic acidosis. Additionally, several deaths have been reported during or immediately following fasting with the etiologies including lactic acidosis, small bowel obstruction, renal failure, and cardiac arrhythmias. Sounds terrifying right? These fasts were all done for EXTENDED periods of time, SEVERAL WEEKS OR MORE which is not the type of fasting I am recommending for health or longevity.
Increased Cellular Adaptation
When comparing mice fed intermittently (restricted eating window and 30-40% caloric restriction on fasting days) to those fed a normal high-fat diet (as much as they wanted to eat) they found lower glucose/insulin levels and increased ketone/adiponectin (marker of increased fat breakdown) levels, while those that were fed unlimited food had the exact opposite and developed obesity. Those mice that utilized alternate day fasts increased their lifespan by 30% and maintained lower body weight and more daily activity than their counterparts.
Effects on your lean muscle mass
Within 6-12 hours of food deprivation, the body begins to upregulate genes within the muscle that increase the metabolic response! How cool is that? It is our safeguard to losing muscle. Therefore, mice that are fed ADF do not become obese and retain their muscle mass due to the intermittent hours of food deprivation. Similar to exercise, fasting activates our AMPK pathway within our muscle cells which promotes mitochondrial growth, cellular clean up and increases our mitochondrial resistance to stress. Certain genes (SIRT3) that protect our muscles from oxidative stress are also upregulated alongside genes that increase cellular clean up within our muscles making them healthier and more efficient (think cellular clean up = less crap/dead cells and oxidation hurting and smothering the muscle cells). Cellular clean up also helps with increased insulin sensitivity and gluconeogenesis. All in all, fasting maintains and protects our lean muscle mass far more when compared to traditional caloric restriction and also upregulates the production of mitochondria which power our cells and allow us to perform at our highest levels.
How about cardiovascular and brain benefits?
One study conducted on mice tracked the heart rate and blood pressure while they had an ADF (alternate day fasting) diet, what did they find? Throughout the first month their heart rate and blood pressure decreased, this was maintained for the following 5 months. The difference between the ADF mice and the eat all you want mice were 100 beats per minute! In addition, the rats increased their heart rate variability and parasympathetic system (that is our rest and digest system).
When it comes to the brain, mice that use TRF (time restricted feeding) experience less cognitive function decline as they age, so their brain works better longer! The mechanisms are unclear but mice that used TRF had better spatial memory and larger amounts of brain white matter (the memory and cognitive function stuff) as they aged. Another study found that mice who used TRF for 3 months experienced an increase in synapse (think the ability for the brain to do more cognitive work) and created more brain-derived neurotrophic factor (BDNF) which is critical for learning, memory and fighting off depression. BDNF has also been found to increase the number of neurons in the brain, the ability of the brain to grow and pushes the signal to grow new mitochondria (there they are again!).
Lastly, perhaps the most important, ADF have been shown to increase certain mechanisms that protect the brain against toxicity and oxidative stress = less aging of the brain and less s risk for neurodegenerative diseases (5). Overall, fasting of any type protects the neurons in your brain, increases your cognitive performance and abilities, bolsters your brain against neurodegenerative diseases through neuroprotective factors and increases the overall capacity and plasticity of your brain.
How fasting changes your body composition
Most of us eat a very Western diet, having 3 meals a day plus countless snacks, eating highly palatable and tasty foods that often come from packages and containers. We eat until we burst and have no need for hunger because food is always available. Doing this causes us to become insulin resistant, which simply means we have so much sugar coming in ALL THE TIME our body becomes numb to the stimulus and begins producing less insulin to deal with the sugar = too much sugar in our blood = inflammation = chronic disease. IF does the exact opposite! IF flips are metabolic switch, regulating blood sugar, increasing our insulin sensitivity and making us very good at dealing with and utilizing sugar (carbs) when we do have them. This lowers our inflammation, reduces blood pressure, and increases our cell’s resistance to stress.
A study of 34 healthy men were split between a normal diet and a TRF (16 hours of daily fasting) for two months. The TRF group showed a reduction in fat mass with a retention of lean mass AND MAXIMAL STRENGTH. When normal calorie restriction is used we see that 1/4 to 1/3 of the weight loss is from lean tissue which over time can affect your overall body composition negatively.
One of the best benefits of fasting is found in the reduction of visceral fat, which is the hardest to lose as it is found within our organs (6). Visceral fat poses the largest threat causing our organs to be bogged down and function sub-optimally resulting in other chronic health conditions. Again, this shows us that fasting can help increase the amount of visceral fat we lose while maintaining more lean muscle mass than traditional calorie restriction diets (I must mention that this is only the case then calorie restriction is done wrong and for an extensive period of time.)
Fasting Allows Your Mitochondria to Grow and Breathe!
Mitochondria are the powerhouses of every cell in our body. Think about mitochondria like the battery in your flashlight or the generator to your house, heck they are the heart to our body. Without them, the cell cannot function, without them, WE cease to survive. Many diseases that we suffer from today our a result of our mitochondria not functioning the way they are meant to, how does that happen? Well think about it like this, every day your cells work, create and do their job, as a result of this, many parts of the cell get warn out, die off or produce excess waste… eventually, this waste needs to go somewhere. If this waste is not cleared out, it is synonymous to taking your trash out of the garbage and setting it in your living room, day after day, week after week. YUCK! The waste builds up, becomes toxic and can suffocate the mitochondria so they can no longer function optimally. When fasting takes place mitochondrial respiration is INCREASED, mitochondria breathe easy and perform their job. In addition, NEW mitochondria are produced when we are fasting, the body is adaptable, it wants to survive so it has safe guards in place to ensure that it does, more mitochondira is one of these safe guards.
At the same time the body upregulates antioxidant activity which lowers reactive oxygen species and lowers overall inflammation within the cells and therefore the body. In conclusion, the healthier your mitochondria are, the healthier you will be and the longer you will live so why not do something that is KNOWN to improve their function and lifespan?
In conclusion, why should anyone consider fasting?
Different than “dieting”, fasting serves as a wonderful alternative to increase your overall health, longevity and quality of life. Most diets are restrictive, too intensive and result in a relapse period of crappy food or binge eating. Fasting allows for a structured framework that can be implemented a few times a month for benefits that reach much further than a number on the scale. If you are someone who needs to lose a few pounds, fasting may not be any better than a normal calorie restriction diet, but if you are someone who needs to lose 15, 20, 30, or 50 pounds I believe that fasting paired with some calorie restriction periods will help you reach results must faster with an onslaught of other health benefits. If you are a hard charging athlete with very high performance goals you need to consider how this might affect your overall performance. I will cover this in post 2, so do not worry!
As we discussed earlier fasting is able to:
Increase cognitive function and performance
Breakdown and target visceral fat and general adipose tissue
Upregulate things such as mitochondrial growth, human growth hormone, and neuroprotective factors
Heal the gut giving it time off from digesting therefore lowering inflammation throughout the body
Regulate blood sugar, increasing insulin sensitivity and increasing someones ability to utilize sugar
Increase cellular clean up throughout the body, therefore lowering toxicity and inflammation
Improve overall health markers such as heart rate, blood pressure and heart rate variability
Allow the body to be more metabolically flexible meaning it can utilize different fuel sources and adapt more easily
Upregulate genes that protect and maintain muscle mass while in a deficit
Upregulate the breakdown and utilization of adipose tissue, lipids and excess carbohydrates found in the liver and muscle cells
Knowing all of these facts above, even if you are someone who only needs/wants to lose a few pounds you can see the numerous positive effects of fasting. Even if you have no weight to lose I would highly recommend fitting fasting into your schedule a few days a month in whatever way you see fit. Unsure how to do that? Ready to find out how you can? Stay tuned for part two in this series where I outline all the ways you could utilize fasting in your daily routine and things to consider while doing it.
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RESOURCES
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Anton, S. D., Moehl, K., Donahoo, W. T., Marosi, K., Lee, S. A., Mainous, A. G., 3rd, Leeuwenburgh, C., & Mattson, M. P. (2018). Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring, Md.), 26(2), 254–268. https://doi.org/10.1002/oby.22065
de Lange P, Farina P, Moreno M, Ragni M, Lombardi A, Silvestri E, Burrone L, Lanni A, Goglia F Sequential changes in the signal transduction responses of skeletal muscle following food deprivation. FASEB J. 2006 Dec; 2014:2579-81.
Arumugam TV, Phillips TM, Cheng A, Morrell CH, Mattson MP, Wan R. Age and energy intake interact to modify cell stress pathways and stroke outcome. Ann Neurol. 2010 Jan; 67(1):41-52.
Neeland IJ, Turer AT, Ayers CR, et al. Dysfunctional adiposity and the risk of prediabetes and type 2 diabetes in obese adults. JAMA. 2012;308(11):1150–9.