Intermittent Fasting

Today in modern society humans spend most of their time feeding, with little time exposed to a fasted state. From an evolutionary standpoint a fasted state was experienced regularly for our preagricultural ancestor because of unpredictable food supply. In this uncertainty, their brains (and those we inherited) developed to be highly adapted to oscillate between fasted and fed states as an evolutionary result. In conclusion this might conclude that fasting periodically is a natural metabolic state for humans to be in.
Indeed, in nearly every major religion a fasting protocol can be encountered as an integral component. Form the Islamic month of Ramadan to the Jewish Day of Atonement, Yom Kippur. In the Christian new Testament, it is delivered that believers would fast before making important decisions. These traditions are seemingly connected by the recognition of psychological and physiological effects of fasting long before science has entered and backed the conveyed tacit knowledge by evidence.
Today there is a growing body of research around the topic highlighting various benefits of a periodical fast when aligned with natural rhythms such as the sleep-wake cycle of the body . In this essay I shall introduce intermittent fasting: Eating in a time restricted fashion without reducing of the overall calorie intake. I will illuminate the origin of the current hype and examine the effects and benefits of fasting along with some practical tips to start with.
This post is thought to a be first introduction and overview of the topic and I will continue to update it as I read further into the topic.

Background

The science behind intermittent fasting (IF) or time-restricted eating (TRE) has been significantly brought forward by the contribution of Satchin Panda, PhD and his work on circadian rhythms. This field of science has discovered clockwise rhythms, spaces of downtime and activity, for nearly every organ in the human body. While we know this for a fact to be true for our brain as we need sleep to reset, science suggests that this also applies for our stomach, heart, lungs the entirety of body cells in general to recover from stress associated with digestion.

Based on this idea a study on mice has been conducted. Two identical, genetically comparable groups were formed and fed with high calory and fatty food. The only difference being one group was allowed to eat whenever they wanted, when the other group was only allowed to consume the same number of calories within a restricted time window of eight to ten hours. Interestingly, over the course of 18 weeks the group without a time-restricted feeding window developed all kinds of chronic diseases: They have become obese, diabetic developed liver and heart diseases much like they are encountered among humans. In contrast, the mice being feed in time restricted manner were completely protected. Reason being, enough time for the organs to repair, reset, and rejuvenate.

This marked a milestone in the history of nutrition science: It has been shown that not only quality and quantity of food matters but also the time window the food is consumed within. Due to the processes involved in digestion and assimilating food, for example producing acid in the stomach.

Do same results apply for humans?

The underlying concept is based on the 24h circadian rhythm, which is conserved between human, mouse, fruit flies, even pond scum. Consequently, results that have been discovered in one system can easily be translated to another system. Indeed, Satchin Panda and his team discovered similar eating rhythms in humans compared to mice. In the conducted study only 10 percent of the people eat for less than 12 hours suggesting ability to the transfer respective findings.

When is a meal fully digested?

Digestion is a fairly long process which takes at least five hours. After this period the body enters a fasted state. For example, if you are eating form 6am to 6pm, after the last bite of dinner the stomach is still busy digesting the food for at least five hours. As a result, the dinner at 6 pm is still digested until at least 11pm for the stomach to call it a day for rest and reset. When breakfast is served at 6am the following day, the organ has had only roughly seven hours of rest time.

Effects of time-restricted eating

A growing body of research suggests numerous benefits of time-restricted eating but the exact reasons are still subject of further research. Calorie restriction has been known to increase lifespan for over 100 years, with the underlying mechanisms remaining uncovered to this day. Similarly, science is just beginning to understand why time restricted eating is beneficial for the health. In the following the observed major effects that have been found in studies are presented.

• Lower Insulin levels and improved gluconeogenesis
  Insulin is a hormone released into the bloodstream by our pancreas when elevated blood sugar is sensed after food consumption. Insulin activates receptors on the surface of cell membranes, to allow sugar molecules to enter the cell where they can be stored or converted to energy. In healthy muscle, fat and liver cells little insulin is required to respond. But repeated and prolonged stimulation of insulin receptors will force the cell to desensitize, reducing the number of receptors. This is referred to as insulin resistance or diabetes.
  Outside the eating window, pancreas gets enough rest to prime the cells to produce just enough insulin when started eating again. As a result, there is no excessive insulin produced time and fasting insulin level drops when in the fasted state.
  Improved Gluconeogenesis: The process of making new glucose starts down during the eating period. In the fasted state the liver does not produce excessive glucose which might explain why glucose levels remain normal.
  -> Fasting can improve insulin sensitivity including the ability to effectively use glucose for energy.

• Increase of functional muscle mass and growth hormone (GH)
  Glucose is made by breaking down protein in the muscle. When the liver is not producing new glucose from protein breakdown of the muscle while fasting for at least half of the day, the muscle must be getting healthier. This hypothesis was supported by various experiments done by Panda et.al as they found both functional and dysfunctional muscle mass in mice increasing when eating in time restricted manner. They found the subjects to show better motor coordination along with enhanced durability.
  Growth hormone (GH)
  GH is known primarily for its role as a repair hormone. GH has natural performance-enhancing qualities, namely its ability to accelerate repair of connective tissue. In addition, growth hormone is also a powerful cognitive modulator, shown to improve many aspects of brain function, including processing speed and mood. Therefore, it is used in treatment of older patients with mild cognitive impairment referred to as pre-dementia. Intermittent fasting is one of the best ways to this hormone.
  -> Growth hormone is neuroprotective and helps preserve lean body mass.

• Enhanced fat loss and cholesterol recycling
  Being in a fasted state there is a high enough energy-deficit to break down fat to derive required energy. When we fast and the fatty acids are transferred to the liver where they are broken down to ketone bodies: Ketogenesis kicks in, which as an alternate “fuel type” for the body to glucose and provides energy the body. In this context, the breakdown of excess cholesterol begins and causes an increase in bile acids soon after beginning a fast. Bile acids are beneficial as they signal the liver to break down fat and produce ketone bodies.
  -> Increases metabolic health including the ability to effectively use glucose and fat as source of energy

• Reduced inflammation
  Studies have shown that markers of inflammation are significantly reduced in humans during Ramadan. In an extended period, intermittent fasting/ time restricted eating combined with a resistance training program is feasible, safe, and effective in reducing inflammatory markers and risk factors related to cardiovascular and metabolic diseases^[1].

• Increase BDNF and neuroplasticity
  Fasting, as a hermetic stressor, is able to turn on numerous repair genes in the body, increasing antioxidant coverage and production of brain-derived neurotrophic factor (BDNF).
  Activity-dependent brain-derived neurotrophic factor (BDNF) has been identified as key regulator of cognitive performance and brain health^[2]. BDNF is known for its promoting function in creating new neurons in the memory centre of the brain, while also protecting existing brain cells. Having higher levels of BDNF bolsters memory, mood, and executive function in short-term along with promoting neuroplasticity^[3] (the brain's ability to change and form new connections, e.g., by learning).

Optimal Duration and when to start eating

Optimal TRE duration for effects

The most popular intermittent fasting protocol is the 16:8 protocol. This entails fasting for sixteen hours, while eating unrestrictedly during the eight-hour eating window. This window can be adjusted to whichever hours work best for you.
For example, a good starting point to begin with, might be a 12h fast, which should be reasonably be achievable for anybody in between 5 to 100 years. Remember not to deprive yourself during the eating window as malnourishment is not aspirational. People with diabetes or other liver diseases might obviously work with their respective physician.
The goal is to regain the critical balance between anabolic (storing) and catabolic (breaking down) states in the body. During the fasting window any drink without calories including black coffee, herbal tea or water is congruent with the intermittent fasting idea.

When should the eating-window be ?

First things first: It is important to make sure you get sufficient sleep of about 7-9 hour per night. After waking up the hormones produced over night for example melatonin slowly decline and day hormones stress hormones are going back up. From a hormonal perspective having breakfast right after we wake up is a bad time to eat because the organs are still trying to adjust to a different hormonal condition. Therefore, eating should be tried to be avoided and delayed for one, better two hours after waking up.
In favour of better sleep, the last meal should be 2- 3 hours before going to bed. Whilst digesting a lot of blood and temperature is rushing towards the digestive organs rising temperature of the core. This is a suboptimal condition to go to sleep in.
Feel free to play around, find whatever works best for you and note that many find not eating for a few extra hours per day easier than trying to track calories (including the author).

Outlook

Time restricted Eating or IF is an emerging field of study. Analogous to the slowly growing awareness to the threats of asbestos and smoking based on scientific findings and the actions being taken accordingly in the past, the benefits of circadian rhythms are yet to be fully understand and implications to be transferred.
Public health is slowly recognizing the benefits of circadian rhythms and corresponding eating windows. Further research is being conducted to understand underlying mechanics of TRE and IF and their use in cure and prevention of disease.

TRE and IF have huge public health benefits. Time restricted eating according to circadian rhythms is a multi-solving solution. Thus, there are few things that we do every day being solutions for many things, TRE or IF are one of them:

• It helps to prevent and accelerate cure from diseases.
• It can be combined with medical treatment to accelerate recovery.
• Rehab: people that have gone through serious health issue, TRE with optimal nutrition bring them back to peak performance.
• To live our peak physical intellectual and emotional performance for our entire life: TRE or IF can help people at every stage at every health condition

Ressources

• The science of time-restricted eating with Satchin Panda, PhD — Diet Doctor Podcast: https://www.youtube.com/watch?v=Mj-qleik1P0
• Lugavere, Max; Grewal, Paul (2018): Genius foods. Become smarter, happier, and more productive while protecting your brain for life.