What to Expect While Intermittent Fasting

What to Expect While Intermittent Fasting

Since our article How to Fast, the Qualia team has finished balancing the holiday feasts with some form of famine (hint: they all survived). With a basic understanding of how fasting works at a high level, we can explore some of the more applicable methods to get started on a fasting diet.

In How to Fast, following the timely Science article “A time to fast”, we broke up the fasting-eating regimens into the following categories:

1. calorie restriction
2. time-restricted eating
3. intermittent (periodic fasting)
4. fasting-mimicking diet

We covered why traditional calorie restriction (CR) of 15 - 40% for an extended period wasn’t an appealing option, but in this part we will explore how some biohackers are inadvertently using this method anyway. Then we will discuss common forms of what tend to be grouped together as intermittent fasting in the biohacking community, the purported fasting benefits, and what you can expect. Our goal is that you’ll have a better understanding of what biohackers are doing (the “what is fasting” part) and how they are doing it (the “how to fast” part). 

A Carnivore Diet May Be A Form of Calorie Restriction

To members of the biohacking community, the carnivore diet surfaces frequently. The diet’s adherents eat nothing but animal protein, with some allowance for animal fat (butter to cook steaks, for example).

At face value, this may seem absurd, but it is growing in popularity among biohackers and high performers.The carnivore diet owes some of its popularity to public intellectual Jordan Peterson2 and his daughter Mikhaila Peterson. She has followed a carnivore diet almost one year and remains enthusiastic about the effects.3

The diet seems more frequently adopted by people with autoimmune diseases. There are currently no studies on how an all-meat diet might affect health, but Dr. Rhonda Patrick has hypothesized that it may have something to do with caloric restriction. See the clip below of Dr. Rhonda Patrick on the Joe Rogan Show between 2:06-6:10 for a deeper explanation:

One of the greatest challenges with classic caloric restriction (How to Fast) is the distraction of persistent hunger. The carnivore diet may overcome this hurdle. By eating only meat, satiety mechanisms prevent adherents from consuming excess calories. By consuming the same food, the monotony drives them to eat even fewer calories. 

Carnivore dieters may be in a state of caloric restriction, but they may be missing out on some of the greatest benefits from fasting. In a 2014 Cell Metabolism study, scientists reported that “Calorie restriction achieved by high-protein diets...had no beneficial effects on lifespan.4 Researchers hypothesized the determining factor in this result was mTOR activation, a protein sensor that modulates the elimination of damaged cells and mitochondria (referred to as autophagy, which we explore more in Anti-Aging Benefits of Fasting).

It is hard to argue with individuals struggling with autoimmune health problems who experience positive effects in their n = 1 experiment, but with no long-term studies and counter-evidence on the effects of longevity, it may be best to use the carnivore diet “in case of emergency.”

Time-Restricted Eating

One of the most common forms of fasting is called time-restricted eating (TRE). Often referred to as “intermittent fasting,” (we are using the Science article’s definition instead) this method restricts the entire daily food allowance to within a certain interval of time rather than the total number of calories. This means an adherent to time-restricted eating can eat all 2,000 calories their body needs to feel satiated, but theoretically see benefits of classic caloric restriction by eating in a smaller time frame.

While the traditional model of 15 - 40% fewer calories leaves the adherent distracted and constantly thinking about food, the time-restricted model provides little mental disruption with many of the same positive health outcomes. Time restricted eating hasn’t been studied for longevity, but there are several benefits on metabolic biomarkers and support for healthy body weight management.5

The Science article mentions that the time-restricted eating window is 4 to 12 hours, but in the biohacker community adherents often choose to eat between 1 and 8 hours of the day (the eating window) and fast between 16 and 23 hours. A common starting point is usually 16 hours of fasting and 8 hours of eating.

This is the most common form of intermittent fasting and one that I’ve been doing for the past 6 years. I’ve found the easiest way to get started is by skipping food before noon and eating until 8 PM. This 8-hour window ensures most social situations (dinner gatherings, for instance) are accounted for while maintaining adherence to the time restricted schedule.

Even though some scientific evidence suggests eating in the morning instead of the evening may support weight management more effectively,6 the best diet is the one you stick to. From personal experience, eating in the evening is more socially acceptable and easier to maintain.

For my workflow, fasting in the morning is better. It allows me to focus on creative, cognitively demanding tasks without the distraction of meals, digestion, or varying blood-glucose levels. 

At the outset, it may seem hard to believe that not eating could provide mental clarity, but the initial hunger pangs subside after the first week or two. This may be a result of normalizing a hormone called ghrelin, which modules hunger based on a circadian rhythm (we get hungry when we expect to receive food). Once you train your body not to expect food in the mornings, most people experience positive cognitive effects.

Intermittent (Alternate-Day; 5:2 IF; Periodic Fasting)

Before we dive in, let’s first clarify the terminology used in the Science article versus standard nomenclature amongst biohackers and wellness enthusiasts. The article groups intermittent fasting (IF) and periodic fasting together (PF) even though they are slightly different. 

Here is the terminology in the Science article followed by the real world applications:

  • IF = alternate day fasting (eat one day and fast the next on repeat)
  • PF = 5:2 intermittent fasting (5 days of eating followed by 2 days of fasting)
  • Didn’t mention = periodic multi-day fasting (fasting a few days at a time every once in a while)

The key thing that differentiates these approaches from time-restricted eating is that they refer to patterns where no calories are consumed for a period of at least 24 hours (and often extending for longer). Keep in mind that it’s not until you get to more than two days when some changes in metabolism start to occur (see How to Fast).

Within these extended fasting periods (3+ days), the body undergoes physiological changes that allow for maintenance, recycling, and repair mechanisms to take over. These processes seem to promote numerous changes in animal models including enhanced brain functioning7, increased synaptic plasticity, and the generations of new neurons (neurogenesis).8 

Doing an occasional intermittent fast for a 24-hour interval is a good place for beginners to start (it is an alternative to the daily time-restricted eating we mentioned above as a starting place into the world of fasting). Depending on your experience with fasting and genetic factors, experiences during a 24-hour fast can range from lethargy and discomfort to relaxation and euphoria.

It may be valuable to consult a doctor during extended fasts (especially if you have a medical condition and are not sure whether fasting would be okay for you), but most young, healthy adults tolerate them well. 

My quarterly 3-day fast provided a post-holiday opportunity to reset. These extended fasts always provide me with a host of new positive and negative experiences. 

The most counter-intuitive experience of extended fasting is the added mental energy and acuity. It is subtle and is most comparable to microdosing psychedelics. The sensation is positive, but the creativity, mental endurance, and deep concentration while fasting seem heightened.

From an evolutionary perspective, this response would make sense. If our ancestors hadn’t eaten in multiple days, it would be adaptive for short-term energy reserves to fuel accelerated cognitive and physical abilities in order to successfully find food. While these mechanisms would be short-lived, in theory they would bring a higher chance of success.9

My subjective energy levels increase the farther I go in the fast. By the morning of day 3 I’ve got so much energy I’m compelled to visit the gym. Even though I take my workout lightly to be on the safe side, I’m a bouncing ball of energy.

Despite an overall positive experience, there are downsides. My endurance for mental work is lower than normal. And the likeness to psychedelics doesn’t end with the positivity and mental acuity. While fasting, I experience heightened stress and anxiety, which can send me into a spiral of existential angst. Consider this akin to being hangry (hungry + angry) multiplied by 5.

I also have difficulty sleeping on each night that I’m fasting. This may be a result of the heightened energy, but evening and bedtime are a bit more challenging during extended fasts. I also find hunger to be more of a challenge at this time, which is consistent with the scientific literature suggesting that appetite peaks in the evening.10

My experience of extended fasting is overwhelmingly positive save for these minor side effects. It’s preferable to do Friday - Sunday so I can avoid too much work interference, but even this time around when working both Thursday and Friday, there were only slight dips in productivity. 

Fasting-Mimicking Diet

Of all the fasting methods, the fasting-mimicking diet (FMD) is the newest one. It was pioneered by biologist Valter Longo. In his book, The Longevity Diet he outlines the premise of a FMD based on research that he and other colleagues conducted.

The largest challenge with traditional calorie restriction is compliance, so Longo and his colleagues developed the FMD, which utilizes low caloric consumption with a specific macronutrient breakdown to generate positive health outcomes (his goal was to make it easier to mimic some of the benefits of fasting and calorie restriction).

To generate similar positive health outcomes, FMD does not require you to go without eating. Longo’s book clarifies a 100% plant-based, low protein, and high complex carbohydrate diet that consists mostly of vegetables and healthy fats (nuts and oils). We recommend reading the book or visiting his website for more clarity on the protocol, but here are some of the basic rules:

  • Day 1: Eat about 1100 calories
  • Day 2 - 5: Eat about 800 calories
  • Drink as much water as you want
  • Having several cups of sugarless tea a day is okay
  • A multivitamin / mineral and omega-3 supplement is okay

For those who prefer a simpler approach, Longo developed a product called ProLon, which is sold by L-Nutra to make the FMD easy to implement.11 The ease of implementation is what attracted one Qualia team member to FMD the week after Thanksgiving.

There are also options to customize the FMD as biohacker Quantified Bob explains in his experimentation here

Despite the (relative) ease, the FMD produces many of the physiological outcomes from fasting. These include regulating low concentrations of insulin-like growth-factor (IGF-1), insulin, and glucose, while elevating concentrations of ketone bodies. In animal models, the FMD can support progenitor stem cells, autophagy (cellular repair and recycling),12 healthful immune systems, and beneficial metabolic outcomes.13

The Benefits of Fasting for Longevity and Beyond

Science has shown positive health outcomes of fasting for over 100 years, but implementation has been challenging. Traditional calorie restriction by reducing calories by 15 - 40% is unsustainable for most people. 

Numerous new fasting diets, based on modern scientific inquiry, create positive health outcomes associated with traditional calorie restriction without the compliance problems. We have described three of the most common methods that are being used by myself, the Qualia team, and many biohackers.

In the Anti-Aging Benefits of Fasting, we will focus on some of the mechanisms that modulate these health outcomes. Even though fasting is the topic of this four-part series, we’ll use these mechanisms to bring you up to speed on the science of longevity and healthful aging.

Get $25 Off Prolon for the Fasting-Mimicking Diet

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For more information on the topic, see our related podcasts:


1 At the time of writing, the Reddit community was over 60,000 members. https://www.reddit.com/r/zerocarb/
2 https://www.youtube.com/watch?v=HLF29w6YqXs 
3 http://mikhailapeterson.com/2018/06/18/6-month-carnivore-update/ 
4 https://www.ncbi.nlm.nih.gov/pubmed/24606899?dopt=Abstract 
5 https://www.ncbi.nlm.nih.gov/pubmed/25470547?dopt=Abstract 
6 https://www.ncbi.nlm.nih.gov/pubmed/29471076?dopt=Abstract 
7 https://www.ncbi.nlm.nih.gov/pubmed/21861096?dopt=Abstract 
8 http://www.pnas.org/content/111/47/16647?ijkey=7c47e78e984c4860ad9333c1da78477d71f06ae5&keytype2=tf_ipsecsha 
9 This isn’t the only evolutionary hypothesis for fasting. Another is located here: https://www.fightaging.org/archives/2018/10/considering-the-adaptive-response-hypothesis-for-calorie-restriction/ 
10 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655529/ 
11 ProLon was studied at USC with positive results. Scientifically designed fasted diet lowers risks for major diseases.
12 https://www.ncbi.nlm.nih.gov/pubmed/28235195?dopt=Abstract 
13 https://www.ncbi.nlm.nih.gov/pubmed/27239035?dopt=Abstract


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