The why
After listening to the Effects of fasting & time restricted eating on fat loss & health podcast episode, twice, I realized that I need to distill my thoughts and take-home messages into a more accessible form. These notes may not make sense to you, so I encourage you to listen to the whole episode and see if they make sense then.
When we partake in diets, this can be due to many different reasons. Most people think of weight loss, but you can also be dieting for fat loss, muscle mass, organ health, genome health (not sure what specifically was meant here), epigenome (I guess methylation of the genome?), to improve exercising, mood, lifespan, inflammation and cognition. I'll touch on a few of these and expand with notes I made.
What is intermittent fasting?
Generally, this is considered a period when you are (not) eating. You can think of it as time of fasting, or, time of eating. This is why I may refer to it as time restricted feeding in this document. This also goes in line with the circadian rhythm of your metabolism and gene activity. Huberman reports that about 80 % of genes have a diurnal cycle. Technically, we're crepuscular animals and addressing this with also your (not) eating window would kind of makes sense.
When you sleep, body is "cleaning metabolic debris" (including autophagy), which can be helped by intermittent fasting.
When we eat, digestion happens (resulting in shit happens), which is an active process. During the process, among other things, inflammatory biomarkers go up and when going into fasting state, these biomarkers subside. This inflammatory process is important when up-taking and digesting food. I can imagine if this happens around the clock that can be very stressful on the body and mind, also contributing to bad mood.
The dos and don'ts
You should have the feeding window set to the more active part of the day. It's very important that you keep it consistent, as by shifting it you will move your body into another time zone. It can take two to three days to get your body (and mind?) back in line. For many people, 7-9 hours of feeding time seems in line with their social life as well as accommodate the acceptable duration between meals. For example, if you start eating at noon, your last bite should be no later than eight in the evening. Many people who do 8 hour eating period actually do more like 9. If you are aiming for 8 hours, do 7 instead. Ideally, you would not eat one hour after waking up, preferably more, and at least two to three hours before sleep.
It takes 5-6 hours to go into fasting state (that is when blood glucose is low). You can accelerate the lowering of blood glucose by some light exercise (i.e. a walk), intensive exercise or using agents. Be warned that using chemical agents like berberine and metformin can have side effects like headaches.
Simple sugars will raise your blood glucose levels the most. This is followed by protein and fat having the slowest effect on raising of the glucose. This is important for breaking fast as 1 g of sugar may break your fast and a small fat heavy meal may not. This depends on the time of day and state of your body. After a marathon, a meal may not break your fast.
Effects on health and cognition
When fasting, we can detect a decrease in p-S6 and mTOR, latter being associated with aging.
It is reported to have a positive effect on gut microbiome, possibly helping IBS (irritable bowl syndrome) patients and patients with various form of colitis. It is said that it promotes the replacement of possibly offending Lactobacillus with species of bacteria associated with healthier gut, i.e. Acidobacter.
Perhaps patients with non-alcoholic fatty liver disease could reap some benefits from intermittent fasting as it promotes the creation of brown fat, which is associated to be positively correlated with the absence of NAFL. Another way of producing brown fat is through cold exposure.
In elite cyclists, time restricted feeding helped increase testosterone and cortisol levels. FWIW, low cortisol levels are suppose to be associated with depression.
Every other day fasting can produce caloric reduction but can be a challenge for at least some to adhere to the regiment.
Time restricted feeding makes it so that you don't have to think when to (not) eat, freeing you from potentially "expensive" decisions.
In states of fasting, fat is a preferred way of increasing blood glucose levels. This happens through increased activity of hepatic lipase and decreased CIDEc (which is lipolysis inhibitor).
Some people find that consuming a pinch of salt (or some lemon juice) helps them huddle through the fasting period. This possibly happens because salt can increase the blood volume.
Time restricted feeding can also help lower blood pressure.