My Experience with the 5-Day Fasting Mimicking Diet

My Experience with the 5-Day Fasting Mimicking Diet

A couple months ago I was listening to an episode of the Kevin Rose Show with Dr. Valter Longo, Director of the Longevity Institute at USC. Here’s the description from the show notes:

Dr. Valter Longo is director of the Longevity Institute at USC and the Program on Longevity and Cancer at IFOM in Milan. In this podcast, we discuss Dr. Longo’s new book, The Longevity Diet, which is the culmination of 25 years of research on aging, nutrition, and disease across the globe.


Dr. Longo has put together a powerful combination of fasting and diet. The diet is that of centenarians (people living 100+ years) combined along with with the scientifically engineered 5-day fasting-mimicking diet (or FMD), done just 3-4 times a year. Dr. Longo designed the FMD after making a series of remarkable discoveries in mice, then in humans, indicating that specific micro-fasts can activate stem cells and promote regeneration and rejuvenation in multiple organs to significantly reduce the risk for diabetes, cancer, Alzheimer’s, and heart disease.

As someone who is lucky enough to typically struggle to gain weight, multi-day fasting is something that never really crossed my mind. But the fact that studies had proven that fasting can have significant regenerative effects and reduce the likelihood of some diseases was very interesting – so I decided to give the 5-day Fasting Mimicking Diet (FMD) a try.

Fasting Mimicking Diet – Quick Overview

So quickly, what is the FMD?

In short, it’s a minimal calorie diet over the course of 5 days that mimics the results of an actual, zero-calorie fast

Dr. Longo showed that these showed these minimal calorie diets had the similar regenerative and rejuvenating effects as the zero-calories fasts, opening the door to many people who may have otherwise been completely intimidated by 5 days of no food (like myself).

Like the title insinuates, you’re mimicking a “real” fast.


My 3 Favorite Benefits of Fasting
(including your cells eating themselves)

I’d always thought the only benefit of fasting was weight loss. No calories = pounds lost.

Makes sense. But while the weight loss is certainly part of the story, these studies have demonstrated some really amazing ancillary benefits including:

Benefit #1: Autophagy (when your cells eat themselves)

This is probably my new favorite phenomenon. Autophagy is when, during a time of nutrient stress (i.e. fasting), your cells start to use the less-optimal parts of themselves for energy and for building new parts

Aka, they eat themselves! Or more specifically, they eat the less useful parts of themselves. What an amazing evolutionary adaptation! By fasting, you’re actually doing spring cleaning on the inside of every cell in your body. This has been linked to such wide-ranging benefits as improve conginitive functioning (see below), improved liver functioning, higher insulin sensitivity (a good thing) and improved body composition.

Japanese scientist Yoshinori Ohsumi actually won the 2016 Nobel prize in medicine for his work uncovering the details of this process. 

Benefit #2: Improved Cognitive Function

Fasting has been related to increased cognitive energy and an increased ability to learn and handle stress. By refreshing your cells via autophagy, you’re keeping things fresh in a vital place where decreased autophagy has been correlated with diseases like Alzheimer’s.

On that note, there have also been studies linking calorie-restricted diets and intermittent fasting to reductions in the neural dysfunction that leads to Alzheimer’s, Parkinson’s and other neurodegenerative diseases. 

Benefit #3: Cancer seems to hate it

A study by Dr. Longo showed that, in mice, the FMD in conjunction with chemotherapy has the potential to expose cancer cells to the immune system. There have also been previous studies demonstrating positive cancer responses using fasting alone as the treatment (again in mice, human trials will take years but the results look promising thus far).

Additionally, the regenerative properties discussed in Benefit #1 have been shown to play a huge role in helping subjects deal with the damaging effects chemotherapy can have on healthy cells.

Bonus Benefit (for me): Hangry no more

I’ve always eaten a lot and have been known to get, er, angry when I’m hungry. Some call it “hangry”. I would allow these negative emotions to completely overtake me and would be become generally unpleasant.

In experimenting with intermittent fasting (12-16 hour fasts; essentially skipping breakfast), I’ve experienced a dramatic reduction in these hangry states. I expect much of the same with this longer-term fast (albeit with perhaps a few ugly episodes in the first couple days).

There are more benefits that have been documented from fasting (slowing age markers, lower cholesterol, better digestive function) that I didn’t list here.


Mimicking the Fast Mimicking Diet

Dr. Longo offers an out-of-the-box solution for embarking on the FMD called ProLon. It costs $300 and nearly every review I’ve read has touted it as extremely effective. And while I have no reason to doubt this, I do have a problem paying $300 for an amount of food that would cost $35 at the grocery store.

Additionally, the internet is awash with smart people who have calculated the macro-nutrient breakdown from Dr. Longo’s original studies, enabling amateurs like me to mimic the FMD and create a relatively comparable experience.

The best documentation of someone mimicking the FMD was from Quantified Bob, which provided an incredible amount of quantified detail on his 5-day fast. I used this as a basis for my experiment.

Here’s the ideal daily calories intake (based on my body weight of 185 pounds):

Day 1 – 925 calories
Day 2-5 – 740 calories

The macro-nutrient breakdown from the original study:

Day 1 -10% protein, 56% fat, 34% carbs
Day 2-5 – 9% protein, 44% far, 47% carbs

So I went out and purchased my supplies for the week which included:

  • 5 avocados (daily breakfast)
  • 1 head of cauliflower
  • 1 jar of Amazing Grass Green Superfood
  • 1 jar of Beyond Raw Precision BCAAs (to offset lean muscle loss)
  • 1 bag of raw, unsalted almonds
  • 1 jar of coconut oil
  • 2 small sweet potatoes
  • 2 Fuji apples (which I would later deem a mistake)
  • 1 bag of spinach
  • 3-4 tsp of olive oil

Green Superfood & BCAAs

That was pretty much it! And after a good meal on Sunday night, I was prepped for Day 1 of the Fasting Mimicking Diet.

Did I also mention that I’m giving up coffee during this 5 day stretch as well? Yeah, maybe not the best timing on that…

(At this point I’m just going to repost the notes I took throughout the process along with my body weight, body fat % readings as well as the actual number of calories I ate that day, broken out via MyFitnessPal)

Day 1 – 923 calories
AM – 185lbs, 17.0%

Morning avocado

7:25AM – Ate my AM meal of avocados and sea salt – feel great. Previous experimentation with intermittent fasting should allow me to make it past lunch without much of a hunger problem.

9:20AM – Once at work, the earliest effect of the diet has surfaced…and it has nothing to do with hunger or food. During this 5 days I also decided to detox from coffee and caffeine, having not gone more than 24 hours without it in my system for 6 months or more. I’m finding it extremely hard to focus, even writing this sentence, without that early morning caffeine pumping through my veins.
1:19PM – Realize I forgot to eat my Greens Powder this morning – that will be my “lunch”. Starting to feel hungry as by this point in the day I’ve usually already had a 1400 calorie smoothie and have been munching on almonds for a couple hours. Had a cup of tea to give me something to sip. Still hard to fully focus and I’ve found myself to be very irritable. Little things that normally wouldn’t bother me – like questions from coworkers, small project hiccups – are now placing me on the verge of sending an email or message that I’d regret! Need to relax.
2:04PM – On the irritability note, just went to GNC to purchase a bottle of BCAAs for the fast and very nearly blew up on the cashier as she tried to upsell me on another brand. Deep breath.
PM – 184.4lbs (-0.6lbs), 16.9% (-.1%)
4:42PM – Came home, ingested my greens powder and BCAAs; felt a little better but then was overcome by exhaustion and fell asleep on the couch for 30 minutes. Felt incredibly sluggish.

Apple Almond Salad – probably too many carbs

6:45PM – Had my dinner of Apple Almond Salad which, while seemed like a lot of food in volume, ended up being south of 400 calories which is quite a drop-off from my dinners which frequently top 1200 calories. (Note from end of experiment: eating an apple during this process was probably too many carbs – would definitely cut that out next time)

8:45PM – Was in bed early because I was falling asleep while reading on the couch.

Day 2 – 775 calories

AM – 183.3lbs (-1.1lbs), 16.2% (-.7%)
7:01AM – Had a decent night’s sleep, but not completely restful. My mind was racing for long periods, often about this diet itself and various things I’d read about it. My solution for that tonight is to meditate before I go to sleep. Feeling a little sluggish but not entirely hungry – decided to do an abbreviated morning workout to get my blood flowing (although exercise is not recommended in the original study, I read another account from a doctor who included light workouts and had good results…I’m giving it a go)

Green Superfood mixed with BCAAs…tasted much better than it looked.

8:03AM – Workout complete, and wowza – could definitely feel the lack of calories throughout. Did a very abbreviated workout consisting of 2 sets of light kettlebell swings, goblet squats, bicep curls and exercise ball sit-ups – this after a good warm up and followed by good stretching. I was sipping on a drink containing 2 servings of greens powder mixed with 1 of BCAAs. Despite the fact that I could feel the early fatigue in my muscles, I’m really glad I did it. Feel refreshed and much more energized to take on the day than yesterday.

11:34AM – Had my avocado breakfast and did some personal work (designing the Sprinter van!) before heading into the workspace. I felt much more energized at this point than I did yesterday, albeit I’m still craving coffee. Decided to allow myself to have a green tea to sip on while working. It contains caffeine but my suspicion was that it will help my productivity – and it did. I don’t feel really jacked up like I do after coffee but have had an incredibly productive couples hours.
1:40PM – Started getting really, really hungry around this time. Went home for lunch of 2 cups of cauliflower which provided some mild satisfaction. Was feeling tired again but after reading for a few minutes, went back to the workspace and resumed work for another 3 hours. Definitely more functional than yesterday.
PM – 182.7lbs (-.6lbs), 16.8% (+.6%)
5:30PM – Ate my dinner of the Apple Almond Salad again, which I was very excited for. 
6:30PM – Attended an event for a program I’m involved with. Required a lot of interaction which I thought might exhaust me but I was actually quite energized and had a great time.
9:45PM – Returned home from event and went directly to bed. Had another weird night’s sleep with my mind racing – did not meditate again though (blaming it on the event). Will do that tomorrow (for real!!)

Day 3 – 760 calories

AM – 183.1lbs (+.4lbs), 15.6% (-1.2%)
6:35AM – Had another weird night’s sleep with my mind racing – did not meditate again though. Will do that tomorrow (for real!!). Feeling sluggish again but pushed through for a very quick/light workout of exercise ball chest press, shoulder press & figure-four sit-ups after warm-up/before stretching. Have been thinking about food quite a lot; Oh! how I’d love to slug my huge 1400 calorie smoothie and a couple cups of coffee this morning. But instead it’s my greens power, BCAAs and an avocado…mmm.
10:34AM – Feeling kind of bleh. Putting out some fires at work without much direction (this may be a bigger issue of work productivity though).
2:49PM – This might sound crazy but I can feel my body changing. A big benefit of fasting is selective autophagy, which is a response your body has to a lack of nutrients (which fasting artificially creates). Your body actually starts using the unusable or malfunctioning parts its own cells as energy or to create new necessary parts; literally biological recycling. The less-than-ideal parts of the cell become expendable which, after a period of fasting, provides your cellular structure of a bit of a refresh. I still feel a little off but feel like the corner will be turned soon and I’ll start feeling the clarity so many fasters speak of.
PM – 183.2lbs (+.1%), 17.5% (+1.9%) ??
4:30PM – I was hammering out work until now. Got into this crazy zone, working with tons of clarity.
5:45PM – Had my dinner of 24 almonds and actually feel really good. Even with Jenna cooking some delicious stir-fry I didn’t really have much hunger surfacing. Surprised how much energy I have.
8:40PM – Meditated before bed! Finally! Planned for 15 minutes but ended up doing 25 minutes – was amazed at how fast my mind was running. Took a little extra time for it to slow down. Now to bed!

Day 4 – 761 calories

AM – 181.3lbs (-1.9lbs), 16.6% (-.9%)
5:30AM – Had a great night’s sleep, finally! That meditation thing really does work. Followed up on some of the work I did last night which had to do with planning my day early – really felt good. I’m actually not hungry at all – had my greens powered & BCAA drink and then actually had to muscle down my avocado. Have tons of energy.
10:13AM – Ran some errands and got to work, banged out a solid 1.5 hours straight of good work. I’m not thinking about hunger at all and still have a lot of energy. I was dying for food at this time on previous days. Decided I’m going to end the fast on tomorrow after doing a full circuit workout.

Coconut oil

12:17PM – Spoke too soon on the hunger, it came back with a vengeance right about now. Granted I was home, near food where I’m usually gorging on a big, awesome lunch instead of my workspace where I could have sat with it and made it go away. But it is what it is. Had my lunch of a sweet potato (100g which is basically just a nub), a tablespoon of coconut oil and eight almonds.

PM – 179.6lbs (-1.7lbs), 16.7% (+.1%)
4:11PM – After eating I feel much better, just a quick spat of hunger. Have been working with lots of clarity and focus since then.
6:40PM – Felt really good all night, had my dinner of almonds and then watched a movie. Did a quick meditation before bed and slept like a baby.

Day 5 – 328 calories (half day)

AM – 179.7lbs (-.1lbs), 14.6% (-2.1%) ??
6:34AM – Woke up feeling sluggish and weak again, not immediately refreshed like yesterday. Stomach was actually grumbling which hasn’t happened very often. Ate my avocado and felt much better. Planning on ending the fast today after my midday workout.
9:15AM – I am really struggling this morning. Couldn’t focus on work, so I reset the morning by going home and ingesting the greens powder (which I had forgot to take). I’m amazed at how much better I feel after taking it. It’s like my body has becoming conditioned to those 60 extra calories the powder provides. 
10:00AM – After returning to workspace I’ve been very productive right up until the circuit workout that will be the fast’s last hurrah. Fingers crossed I don’t pass out.
1:14PM – Made it through alive. Kept the weight relatively light but completed a 40 minute pull-focused circuit workout. Was sipped on a mix of BCAAs and greens powder through, think that helped a lot. Thought I’d be sprinting back to my house to eat but the hunger is actually non-existent; figure I need to get to the food considering the strain of the workout.
PM – no readings, fast OVER!
4:15PM – A lot of people have reported not having much of an appetite once completing the fast. I am not one of those people. I started with two eggs and two pieces of toast but proceeded to scarf another egg/toast pair, apple, peanut butter and these amazing gluten free crackers from Costco (Milton’s – they’re seriously amazing). I was worried I’d make myself sick but I actually feel really good – like my body is being revitalized. Here’s the lower half of my Friday nutritional details…
I know the actual ProLon diet has a transition day after the final day of fasting but my version doesn’t, I’m getting right to it….I’d barely eaten in 4.5 days, give me a break!

FMD Results & Observations

Overall, I found the Fasting Mimicking Diet to be a challenging but doable endeavor. The main obstacle for me was the sluggishness I felt at some point on all the days; but who knows how much of that was the FMD and how much of that was caffeine withdrawal (again, probably not an ideal time to stop drinking coffee).

The tiny meals actually end up not being that big of a deal. Once you first through the first couple hunger pangs and watery mouths, the hunger becomes less and less of a consistent issue (although it does pop up with a vengeance from time-to-time).

There were a few instances (mostly on Day 3/4) where I had these amazing moments of clarity that resulted in some really quality work or personal insights. As I mentioned in my notes, I really did feel my body changing which I think had to contribute to these brief flashes of insight.

As for the two metrics I was tracking:

Body Weight: -5.3lbs (-1.06lbs/day)
Body Fat %: -2.4% (-.48%/day)

The body fat readings were done with a handheld Omron device at woefully inconsistent times and physical states (see Lessons for Next Time below) so while I have no doubt I lost body fat (I look leaner), I have no idea how accurate those numbers actually are.

I’m writing this recap 3 days after my fast has ended and my body weight is already back to 183.4lbs (granted, after a weekend of heavy eating and drinking…) which has helped alleviate my concerns about losing too much weight.

But in conclusion, I will absolutely be doing the Fasting Mimicking Diet again. It does require some effort, but the results of fasting are undeniable and well-worth the short-term discomfort.


Lessons for Next Time

There are several significant ways I’m going to improve my FMD when I take it on again in 3-4 months (Dr. Longo recommends it every quarter):

  • Take measurements at more consistent times & physical state
    • My body fat % was all over the place, most likely because of lack of consistency
  • Get blood testing kit
    • Interested to know what was happening in my blood (ketones, etc)
  • Eat more fat, less carbs
    • I realized that my macro-nutrient breakdown was skewed too much towards carbs in the first two days; plus I’d like to try and all but eliminate the carbs to really maximize the process
  • Exercise regularly
    • I’d be interested to see what keeping my normal workout plan would feel like, even if it’s not recommended.

Quick Update from Following Week

It’s Tuesday of the week following my 5-Day FMD and my body has actually felt very fresh. I had lots of energy this week (probably too much, leading to a late karaoke night…) and a strong workout on Monday.
This certainly could have been the result of a week where I did very little to stress my body but it just as easily could be the rejuvenating effects of the FMD.

Thanks for reading!

Posted by on March 5, 2018