@tino-wenderoth

Yes, it technically breaks your fast as it has calories and triggers some insulin response. But here's what I learned: when I skipped glycine to keep my fast "perfect," I'd sometimes lie awake for hours and feel like garbage the next day.

When I started taking it again during fasts, my sleep improved dramatically and I felt way better overall. Poor sleep screws with your hormones and recovery in ways that probably cancel out most fasting benefits anyway.

Only my 2 cents: I would take the glycine, get good sleep, and don't overthink it. The sleep quality win beats the minor fast-breaking downside by miles.

If you sleep fine without it, skip it. But if it's the difference between solid rest and stressing about amino acids all night, just take it and move on.

What do our fasting experts say?

@bastian-mayerhofer
@heiko-bartlog
@brgmn
@ronald-tenholte
@hadi-saleh
@matthias-buchhorn

I skipped glycine during my FMD!

During my everyday intermittent fasting, I take it some days and some days I don't. I usually sleep well with or without glycine. I don't take these daily fastings too serious any more - if it's 12 or 16 hours - I'm just not hungry in the mornings 🤷‍♂️

@tino-wenderoth @karol

I'd agree with Karol's take. Good sleep is a lot more beneficial than intermittent fasting, especially considering the following:

1. The idea that macroautophagy ramps up during intermittent fasting goes back to an erroneous translation of mice data to humans due to different metabolism and lifespan. The actual timeframe is rather 48-72 hours for humans. That's why most fasting programms last for roughly 5-7 days. Macroautophagy is peaking around 72 hours and slowly recedes afterwards (generalizing a bit here).

2. I do not recommend 16:8 IF to most of my clients anymore. There are, in fact, short-term benefits (like weight loss and improved insulin sensitivity) associated with it. The latest research, however, indicates what some researchers have suspected for a while: Not just the omission of breakfast is deleterious to long-term health outcomes (which has been shown in numerous studies), but the short eating window (≤8h) itself is harmful in the long run, with a 91% increased risk of CVD/Death.
   
   https://newsroom.heart.org/news/8-hour-time-restricted-eating-linked-to-a-91-higher-risk-of-cardiovascular-death
   
   This study is not fully published and peer-reviewed yet and has some (common) limitations, but seems to indicate that a 12-14h eating window seems a lot more beneficial in the long run.

I like to think of this development as "You can have your cake and eat it, too" as research seems to indicate that you can get the short-term benefits of IF with a 12-14h eating window while optimizing for long-term health and at the same time enjoying food without stressing out about an unnecessarily large daily fasting period.

Just stumbled upon an article with the following conclusion: "Intermittent fasting restored the circadian rhythms of many previously dysregulated genes in the memory center of the brain in Alzheimer’s disease, including genes known to play a role in Alzheimer’s disease." Source: https://staycuriousmetabolism.substack.com/p/intermittent-fasting-reprograms-the?r=40ekz2 (Nick Norwitz)

sorry for jumping in on this with some delay, many thanks for the great insights from everyone already. I am not an expert on ammino acids, but I can also add some comments from the FMD / Valter Longo Perspective on this, but mainly confirming the previous comments:

- benefits of 16:8; yes as it mostly is the case, there are so many pros and cons when summarizing the research literataure about IF with 16:8 or more. (possible negative effects are mainly due to possible stress increase via cortisol levels rising), especially given that the most relevant levels of autophagy might not be achieved via 16hours ... so Valter Longos take is to recommend 12 hours over night fasting, everything loger depends on many individual factors and goals, e.g. it might be good for a calory deficit, but might come with other trade offs ...

- glycine and (prolonged) fasting (3+ days — according to Longo 5 days the best tradeoff between reaching optimal levels of macro-autophagy, stem-cell activation ... but not risking excessive muscle loss on the other hand) or in combination with the FMD: really not sure about this, on the one hand, the glucose response with Glycine as well as mTor / IGF1 response might be very little, it probably would be better to pause it for the period of your prolonged fasting window.

the main principles behind the FMD is reducing protein intake, low carb intake, high fiber, high fat and low calorie, it is already composed in a way to narrowly stay under the radar, so any additional intake might risk your fasting benefits.

but I align with the other commets: do not stress yourself about the 16hrs window, it seems more important to focus on the sleep quailty and muscle support.