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Review: 5 days on the Fasting Mimicking Diet

One of my favorite podcasts to binge lately is The Peter Attia Drive Podcast. It's all about increasing longevity and healthspan. A point that he comes back to time and time again are the longevity benefits of fasting (autophagy, fatty liver reduction, better pancreatic function, lowers insulin levels). Not just time-restricted or "intermittent" fasting that is all the rage right now, but several days (minimum of 3) straight of fasting.

Over the past year I've tried several times to do a 3-day water-only fast and each attempt has been a complete failure. I invariably find some excuse around lunch time on the first day as to why this actually isn't a good time for me to attempt a fast. The first real strong pang of hunger has just been too big of a hurdle to get over. So when I heard about the Fasting Mimicking Diet on the Tim Ferris Show, I felt like it might finally be the thing to get me over the hump.

What is the fasting mimicking diet? So, this longevity researcher did a lot of studies to find out what is the most amount of food you can eat (and which types of foods) while still getting the majority of the benefits of fasting. Turns out, it's actually a reasonable amount. This is why it's called the fasting mimicking diet - it's a five day diet whose effects mimic that of a water-only fast. The exact foods change a bit from day to day but it's an all vegan mix of nut bars, vegetable soups, teas, and a few snacks thrown in the mix.

Here's everything I ate in those five days:

Just how much food is this? It's about 1100 calories worth on the first day and then 750 each subsequent day.

Day 1

The first day really isn't that bad. The worst part is the olives because olives are truly disgusting. 1100 calories worth of food is actually a reasonable amount so the hunger wasn't ever really a problem.

I even had a hockey game that day and felt perfectly fine before and after.

Day 2

I started the day a little nauseous which may have been a bit of "keto flu". It subsided quickly enough and never returned.

The second day was the first of four days on the hunger rollercoaster. It would come and go throughout the course of the day but not at the times I expected it to. I was never hungry when I woke up or right before bed -- 3pm and 8pm seemed to be the worst times.

Eating a little for lunch and dinner certainly helped, but I was surprised that often hunger would come and go on its own. I wonder how much of it is a learned behavior, and that maybe future fasts will be even easier?

I was also surprised at how manageable the hunger was, never really getting worse than moderate annoyance.

Day 3

I finally wake up in moderate ketosis for maybe the first time in my life. Seems kind of odd or impossible that this is the case but I don't know another time in my life that I would have abstained from carbs for long enough for this to happen. Based on the pee strips I used, I was at around 1.5-2 mmol/L which is solidly in the ketosis zone.

I made the terrible, terrible, terrible mistake of going to the grocery store this day. Let me tell you how bad it was. Just seeing some of the foods caused a literal pain of desire in my chest. The thought of eating was about as much as I could bare and I came close to calling it quits. I was surprised by how much I wanted a frozen pizza but also how Oreos were only moderately desirable (though, to be clear, I would have still eaten a whole package).

Day 4

By day 4 I'm just frustrated with the coming and going hunger. Not because it's particularly painful but because it makes it hard to really concentrate on anything for a long time.

I went into the co-working office  and forgot the lunch/snack for this day's box. I got a side salad with avocado and decided I'd just skip all of the rest of the food provided for this day.

Day 5

The last day feels a lot like day four which is kind of a relief. Throughout the fast I kind of expected every day to be a little bit worse but the pain actually caps out pretty quick.

I really started fantasizing about what I'd eat when it's over, even though I knew I should take it easy and not go crazy the moment I could.

Transitioning out and plan going forward

Sweet, sweet freedom. I actually ate pretty reasonably the first day off the fast. For breakfast I had a scrambled egg, half an avocado, and some blueberries. For lunch I had a Mediterranean chicken salad. I honestly don't even remember what we had for dinner but I'm sure it was pretty tame.

I'm planning on doing this once per quarter with a few tweaks.

1) I'm going to try making all of my own food for this. I think I could make a better tasting and less expensive version (the Prolon kit was $250) of this myself.

2) I'm going to get into or close to ketosis beforehand. I think it might make things a bit easier not having to deal w/ the effects of a fast and keto flu all at the same time.