Experiment: Fasting Mimicking Diet

About three years ago I read Longo’s Longevity Diet, and it helped me form a foundation about nutrition. Ever since reading it I have been wishing to do a FMD, but training, travel, or life always got in the way. I decided it might be a good match to try and eat slightly in surplus, and then do the fast once I hit the goal weight.

Exactly as per the plan I added about 2.5kg by the end of June, so decided to go ahead with the fast. Coincidentally ProLon, the company that helps make FMD kits, had a 30% sale, so I got my kit and chose the week to give it a go.

I did a 14 day fast when I was a teenager based on a dare, so somewhat knew what to expect: the first few days aren’t great, but then your body adapts and things are easier. I also knew that after the fast appetite would be suppressed for a few days. Unlike when I did the dare as a teenage this fast was actually backed by evidence:

https://www.science.org/doi/full/10.1126/scitranslmed.aai8700

The fasting-like diet reduced body weight and body fat, lowered blood pressure, and decreased the hormone IGF-1, which has been implicated in aging and disease. A post hoc analysis replicated these results and also showed that fasting decreased BMI, glucose, triglycerides, cholesterol, and C-reactive protein (a marker for inflammation).

https://www.nature.com/articles/s41467-024-45260-9

Based on a validated measure of biological age predictive of morbidity and mortality, 3 FMD cycles were associated with a decrease of 2.5 years in median biological age, independent of weight loss

Journal

Day 1

I skipped breakfast, already knowing I would prefer to bunch my calories and lunch and dinner, and waited until about 11:00am to open the box. Everything is laid out nicely, and it is pretty clear what to do. If you’ve ever made soup before, then you can do this!

Feeling for the day was pretty good. I was in a calorie deficit from both days over the weekend, due to being quite active, which I think helped ease me in to a real fast. It helps being at least a little fat adapted, so you might want to ease back on the carbs the week prior and instead swap in more fat.

Day 2

Slept amazing the night before; according to Garmin it was the best sleep I’ve ever had; they even gave me the “mythical sleep” badge! I don’t know if I would say it is the best sleep I’ve ever had, but it was very very good. Mildly hungry. Went to the gym and did a light leg day, burning about 200 calories while working out.

Day 3

I knew this would be the hardest day, and I think I was right. Slept average the night before, and feeling more fatigued. Brain fog has kicked in. In retrospect I even made one small mistake at work, which (I don’t think) tends to happen that frequently.

Day 4

Slept better the night before, and hunger levels have decreased. It is a weird feeling knowing you’re hungry, but not really feeling hungry. Brain fog has gone away.

Day 5

Felt like I slept OK, and long, but back got a little sore and it woke me up a few times. My body probably isn’t used to this little activity and sitting around. Mind feels crystal clear.

Day 6

Slept OK. Wasn’t hungry when I woke up, but excited to be able to start training again! The transition day seems to be aimed at getting one’s body ready for whole foods again, and trying to get people to eat healthy. My regular diet is pretty good, so I am opting to skip the soups and generally resume eating as normal. I had a giant salad for breakfast.

We can see the dramatic drop in calories by this chart (from 21-July-2025):

Reflections

I had the privilege to be able to use a glucose/ketone meter to track my progress, and wish I had recorded it on the first morning so I could see it rise. It looks like I was in ketosis on every measurement. You can see how I did in this chart:

Overall the fast went well, and I don’t think I burned any bridges by being too grumpy! I stopped running during the five days, but I tried to do some strength training to prevent muscle loss.

Did it work? What does work even mean? Can I even measure autophagy?

I don’t know the answers, but in two weeks I’ll get my blood checked to see if my biomarkers improved.

My weight did decrease, which you can see in this chart (my goal was to get to 80kg before starting the fast), but then quickly rebounded, I presume from resuming creatine consumption and getting water in my muscles again.

Day 2’s morning weight measurement was 77.1, and Day 6’s morning measurement was 75. I suspect that when I weight myself tonight it will be around 76 - 76.5.

Tips

Are you thinking of doing the FMD? Here are some tips:

1. If using ProLon, add water to your soup as per the instructions, and use a whisk to mix it. Then let it sit for at least 15 minutes, and use a whisk again. This makes sure it is totally mixed.
2. Give yourself permission to take it easy. I stopped running entirely, not because I couldn’t, but because I don’t want to burn those calories. If I had excess weight to lose then I would consider exercising.
3. Consider having most of the calories around dinner time, as this will prevent you from feeling too hungry when you fall asleep, which for me is a feeling I don’t love.
4. It is possible to DIY FMD, which I’d consider doing next time. I actually think that might be an easier way to have food with more volume, which might help with satiety.
5. Stop drinking water/tea relatively early. For some reason even though I stopped around 7pm on Day 2, I ended up needing to pee in the middle of the night twice.
6. Make sure you’ve got the right mindset going in to this thing. Be fully bought in to why you’re doing this, and remind yourself that the discomfort is an opportunity to teach yourself more resilience. Embrace the suck.
7. Stop drinking liquids really early - even earlier than you normally would. I was stopping 3hr before bed, as I normally would, and I still had to pee almost every night, I think, which is pretty unusual. One night I had to pee twice.
8. It is only five days. Take a photo of your accomplishment! You got this.

Reflection

A challenging quarter, as I spent three three weeks travelling; it took me at least a week to start feeling normal in each direction, and much longer to recover. Additionally, because I was leaving for such a long time, I think my work/life balance suffered prior to the trip. However, physical health isn’t the only thing that matters, and I think travelling helped me and my family grow.

I finished some more Longevity-related books, like Longevity Leap, and then also The Art of Dying Well. I’ve also started learning more from Michael Lustgarten. In particular I like his minimalist approach and lifestyle, and that he prioritises whole foods over supplements.

Focus Areas

This quarter I had a several areas I wanted to focus on:

1. Improve fitness by training more. My goal is to get above a 75 fitness score on intervals.icu, and still maintain 3+ gym sessions per week.
2. Gain weight by starting to track my food in Cronometer, again, and not eating out anymore.
3. Sleep better by improving my sleep hygiene (starting wind down by 8pm, in bed by 9pm, wearing red light glasses at night, and increasing glycine consumption before bed). I also experimented with taking Magnesium Glycinate before bed.
4. Reduce Stress by being mindful of when I eat my meals, and what meals I’m consuming. Additionally, wherever possible, avoid evening meetings.
5. Improve Biomarkers by looking at my nutrition, as well as the above items.

Let’s go through what I experimented with, and the result.

Improve Fitness

My main forms of exercise remain running and strength training. There are two tools I use:

1. Garmin’s Intensity Minutes (and other metrics)
2. intervals.icu

Both of these tools help warn me of overtraining, but also lets me see the impact of my planned workouts. For example, as of today (7-May-2025), here is my plan for the rest of the quarter and showing the previous two years of training:

My goal was to get above a 75 fitness score according to intervals.icu without injury, and to average above 800 ‘intensity minutes’ according to Garmin. In Intervals.icu, the “fitness” score, also known as Chronic Training Load (CTL), is ==a measure of your average training load over the past six weeks==.

Results

• Fitness score of 75 or above ❌
• Average intensity minutes of 800 or above ✅
• Improve Vo2Max ✅
• Decrease RHR ❌

So, how’d I do? Let’s look at the previous 3 months in intervals.icu. My goal was to get above 75 ‘fitness’:

And I only got to a 71. The main setback seemed to be the 3 week trip I took to Europe, as I tried to keep up with my fitness, but in some instances it was just too difficult. Additionally, I think the challenge was as much the jet lag as the trip itself, as it took a while for me to get my circadian rhythm back in sync.

Here is what my ‘intensity minutes’ look like for the previous 12 months, which also shows my dip in Dec/Jan while I was travelling, and to a lesser extent in April when I was travelling again:

My fitness routine remains similar to the previous quarter.

RHR: My average resting heart rate was 52. This is a slight increase from 48 back in late February, and with another dip to 49 in late April. I think RHR is impacted as much by training load as other stress factors.

Vo2Max: My Vo2Max according to Garmin is now 52ml/kg/min. This has been consistent for about 4 months now, and is a little higher than the 51ml/kg/min

Gain Weight

Plan

My previous DEXA saw body fat % decrease, but also a slight decrease in lean muscle mass. This is somewhat confusing to me, as I’m lifting heavier than ever before, but apparently that can be purely neuromuscular.

I’m also confused because my weight hovered between 76 and 78kg for the previous 12 months (screenshot from end of April).

Regardless, to maximise my chances of building muscle I need to be in a calorie surplus, and I suspect that when things get busy, given I try to avoid eating out (as well as how expensive it is!), I sometimes don’t get enough calories.

Enter Cronometer. I had previously used this tool to look at my micronutrient profile, so I could fill those gaps with supplementation, so I resumed using it this quarter. The below image is from early May targeting 80kg by the end of June.

Early on I was having trouble hitting the calorie target, as can be seen from this random day of food tracking from Cronometer.

We can see from this that my protein consumption is adequate. I still wished to remain on a whole foods plant based diet wherever possible. Unfortunately, I’m not really driven by food, and I don’t believe my mood is negatively impacted by being in a slight calorie deficit; in fact, I generally don’t even notice besides perhaps my runs being harder, or potentially not sleeping as well. This means that without tracking my consumption it is difficult for me to be in a surplus.

Towards the end of May I started to dial in meal prepping, and getting in a better habit of what foods to bring. By the end of the quarter I was almost able to even hit my calorie targets even on long run days, which is up to 5000 calories!

Results

• Increase weight ✅
• Increase muscle 🤷

I gained weight almost exactly as Cronometer predicted, which is exciting.

I didn’t need to do any major tweaks to my diet, just a few extra calories per day. I have a hypothesis that too many extra calories (e.g. 300+) starts to impact my sleep, so sticking in the 100-200 extra calorie range seems to be the right zone to build muscle, but also still be able to sleep well.

Sleep better

Plan

The National Sleep Foundation (NSF) has a long list of tips ([[https://www.thensf.org/sleep-tips/]]), but I follow all of those. In addition to these tips, I also:

• Get light between 5:30am and 6:00am
• Wear blue light blocking glasses after about 7pm
• Observe the 3-2-1 rule (3 hours before bed: No more food or water. 2 hours before bed: No more work. 1 hour before bed: No more screen time.)
• Take 5-10g of glycine per day
• Sleep in my own bed (except when travelling)

Overall, I fall asleep quickly each evening. However, the challenge that I need to overcome is that I sometimes wake up at 3:30am - 4:00am full of energy, and rarely wake up after 6am. Although this usually still allows for a healthy sleep duration of 7-8 hours, I would prefer 8+ hours if possible. However, the challenge is when I wake up at 4am and can’t get back to sleep.

One observations I had is that I might get in to a vicious cycle: I wake up early, eat food, and then the night night wake up again… hungry. Repeat. One thing I changed this quarter was eating at the same time every morning even if I woke up early.

A note about glycine: I think I need to have a routine where I have it just after dinner, as otherwise I get pretty sleepy during the day. More experiments needed.

Results

• Improve sleep quality ❌

It looks like sleep duration was worse across the board. Note: this is not time in bed, but what Garmin records. I’m especially confused by the one on Tuesday, and that will require additional exploration.

We can also see this with the Body Battery stats; whatever I was doing in February and March seemed to be helpful.

It looks like upon returning from my travels to India at the end of January I had two months where I balanced sleep and exercise quite well, but that started to erode in the lead-up to travelling to Europe.

Decrease Stress

Plan

I had a desire to decrease stress this quarter, but at the same time I didn’t really have a plan of how to make it happen. One area of focus was to avoid late night meetings wherever possible, as I have found that they tend to impact my sleep.

However, because this was an area of focus, I did attempt to be mindful of what caused stressed. One area that I am actively exploring is the impact of food on my ‘stress’ metric, and I’m starting to see a pattern that meals with a lot of carbohydrates (e.g. 250g of gnocchi or 150g of dried pasta, or a significant amount of white rice) seems to trigger a response. Although I don’t eat white rice at home, sometimes when eating out I didn’t always have a choice. Switching to brown rice appears to help.

Results

Overall it looks like I was more stressed this quarter than last quarter, but that could also be because of other factors less in my control - I see a pattern that most years Dec-March my stress levels are the lowest in the year.

The heatmap below is a great way to see how the quarter played out.

Some of the larger events in this quarter really stood out, such as:

• Week 15 is when I flew to Europe (the Thursday)
• Week 18 is when I arrived home (the Sunday)
• Tuesdays (after returning) are usually a hard day for exercise, where I do some kind of harder run (e.g. 4x4) and do a leg day.
• Sundays are usually when I do a longer run

I’m a little curious what changed between Q1 and Q2 when it comes to Tue/Thr, as these were previously my least stressful day of the week.

I still have more work to do when it comes to reducing stress levels.

Improve Biomarkers

Plan

And then what really matters - improving biomarkers. This is ultimately an outcome of achieve a number of the above items as well nutrition. One area that I think I’ve done really well on since returning from Europe was eating well; sufficient protein, lots of fibre, avoiding dairy, and minimising saturated fats.

Results

I’m going to start tracking PhenoAge on a quarterly basis, as long as I can keep getting tested without too much drama. Here are the results.

Compared to my previous test we can see that:

• Albumin: 4.53 → 4.00 🔴
• Creatinine: 0.76 → 0.81 🔴
• Glucose: 88 → 88 ⚪️
• CRP: 0.3 → 0.7 🔴
• Lymphocyte: 27.4 → 44 🟢 (however, I had to calculate the % from the absolute value, so this might be entirely wrong)
• MCV: 93 → 95 🔴
• RDW: 12.6 → 12.8 🔴
• Alkaline Phosphatase: 75 → 60 🟢
• WBC: 6.6 → 4.1 🟢

Although none of these changes are significant, it is absolutely the wrong direction. There are two explanations: (1) I did the blood draw too soon after finishing my FMD cycle, and (2) I had been feeling a little under the weather the week before.

I’m reminding myself that this isn’t a sprint, but a marathon, so we can keep refining as we go along. Next round of testing will hopefully be better!

This Quarter’s Supplement Stack

Some principles that I tried to follow:

• Avoid bill burden
• Wait until a supplement is on the ITP supported interventions page
• Have a biomarker in mind that a certain supplement will change.

And here’s what is currently in my stack:

I swapped out the B Complete with a B12 (methylcobalamin) and L-Methylfolate combination. I’ve added in iodine (via kelp) now, too, given I’m essentially on a vegan diet and don’t eat much salt.

When looking at Cronometer the only vitamin that I am routinely shot on is Vitamin A, so I need to figure out a way to get that in my diet. If possible I prefer to get it via food instead of supplement.

Experiments

Fasting Mimicking Diet

I conducted one experiment this quarter: the Fasting Mimicking Diet.

You can read more about my experience here: https://www.kelvinism.com/2025/07/prolon-fmd.html

Did my biomarkers get better? There are so many variables this quarter that it is hard to point to this one experiment calling out if things got better or worse, but it helps to at least look. How soon should I test after a thing like this without screwing up the results? According to one of the FMD studies linked above, and another study that I vaguely remember about testing after Ramadan, I seem to remember in their methodology the researchers waiting 8-12 days before testing.

After waiting 8 days I was able to take my blood test, and discovered that my PhenoAge… got worse! Check out the Biomarkers section for more details.

Heavy Metals Testing

While travelling in India I was able to do a blood test that included testing for heavy metals, and the results were generally unremarkable with the exception of Caesium and Beryllium.

To corroborate these I also did a Hair Tissue Mineral Analysis test via ToxTest, and here are the results:

From what I could research none of this should actually cause me to lose any sleep, and HTMA isn’t really that proven as a diagnostic tool. The Uranium and Thorium level are a worry though, but given my blood results were acceptable I am just assuming I went somewhere hiking that had higher levels radioactive elements.

Focus For Next Quarter

I think the next quarter will remain similar to this one. Cronometer is working really well for me to be able to control my calories, and to force me to eat from a list of known ‘good’ food. For example, if someone offers me some kind of snack, then I’ll probably skip it purely because of the pain of needing to try and keep a record.

The biomarkers that I will specifically target include, in order of priority:

IGF-1: This is potentially from eating too much protein. I’ve removed pea protein from my smoothie, as well has the HCP. Let’s see if it drops.

MCV & RDW: Seem potentially related to being slightly off. I’ve got an experiment in mind, too. Need to optimise b12 levels, I think.

Albumin: Potentially related to FMD.

hsCRP: I’ve had it at 0.3 several times before, so I know I can get it that low. Potentially related to FMD.

Background

I have a journal of all the travels I did when I was in my 20s, and sometimes it is enjoyable to re-read the various journeys that I went on. In those entries I could see my writing change, both in voice and theme, as I gained more life experience.

Recently I wrote about my health journey in 2024, and I have a goal to write a quarterly entry. This is the first entry of what I hope to be many entries.

Now that I have returned from some travels in India I have been able to focus more on my health. I have returned to a diet lower in saturated fat, and been able to generally increase the amount of exercise that I have been doing.

Experiments / Focus Areas

This quarter I had a few experiments.

1. Train more by getting up to 60-70km/week running, and get in the gym 3-4 times per week. I should see my Vo2Max increase, and RHR decrease. The goals here are to build muscle, bone mineral density, general cardio protection, and sleep better.
2. Sleep better by meditating before bed, starting wind down by 8pm, and increasing glycine consumption before bed.

Train More

Here is what my ‘intensity minutes’ look like for the previous 12 months, and you can clearly see the impact of travelling in Dec/Jan:

And then the previous 3 months in intervals.icu. My goal is to get to 80 Fitness and stick there for the rest of the season.

My target fitness routine remains the following:

Monday

• Easy Run (~8km)
• Resistance Training (upper)

Tuesday

• Hard Run (Vo2Max 4x4)
• Resistance Training (lower)

Wednesday

• Easy Run (~8km or longer)
• Resistance Training (core)

Thursday

• Hard Run (Nx1000, or a beach tempo run)
• Resistance Training (lower)

Friday

• Easy Run (~8km or longer)
• Resistance Training (upper)

Saturday

• Long Run

Sunday

• Play Day (swimming or a hike or walk somewhere)

Many weeks I only achieve about 90% compliance, e.g. today I had a DEXA scan so couldn’t do my morning run, and then had blood work so skipped the gym. I’ll likely still walk home to make sure I get my 10,000 steps in.

Sleep better

In addition to increasing my glycine consumption I’ve started reducing the amount of liquids I drink after dinner, to good results of needing to wake up and go pee. I also purchased a pee jug as a further experiment.

One observation I made is that for two evenings I played a computer game until close to bed time, so missing wind down, and I think it severely impacted the quality of my sleep. I didn’t go to bed any later, but I think all the light impacted my circadian rhythm. I have purchased some clip on blue/green light blocking glasses to see if that helps, although I’ll be avoiding playing any games for a long time (it is about a once/year type of escape). Interestingly, my HRV started dropping after that, too, but perhaps that’s just a byproduct of sleeping slightly worse.

Speaking of circadian rhythm, given it is soon winter here in Sydney, I wanted to get a light to trigger cortisol production first thing in the morning. Given it is an experiment I purchased some LED lights in the right wavelength from AliExpress, taped it in a metal mixing bowel, and put a plastic bag over it. I had the 12v PSU already. I think it is helping, and I start getting pretty tired by 9pm, and I’m often lights out by 9:30pm. I usually wake up around 5:30am, but sometimes when my “body battery” is full at 5am or earlier I’m wide awake and ready to go.

This Quarter’s Supplement Stack

Some principles that I try to follow:

• Avoid bill burden
• Wait until a supplement is on the ITP supported interventions page
• Have a biomarker in mind that a certain supplement will change.

And here’s what is currently in my stack:

My Nutty Pudding also has TMG, Creatine, Pea Protein, Taurine, and HCP.

Results

• Increase weight ❌
• Increase muscle ❌
• Increase BMD ✅
• Improve sleep quality ✅
• Improve Vo2Max ✅
• Decrease RHR ✅
• Improve LDL ✅

Weight/Muscle: Unfortunately, I had mixed results. My DEXA scan results showed that while my body fat % decreased from 18.5% to 17.7%, my lean mass also decreased. This is a bit puzzling given my weight has remained stable and I’m strength seems to have increased since a year ago, but perhaps this is all neuromuscular. My main takeaway from the DEXA is that I need to eat more, which is hard, because I feel like I’m already always eating. This will be a goal for the next quarter.

BMD: Increased from 1.116g/cm^2 to 1.130. I’m not certain the machine’s variance in accuracy, but I’ll count this as a win.

Sleep: Usually I wake up with a 100 “body battery” according to Garmin, which might be a better indicator than my sleep score. My average sleep score since coming back from travelling was 87, but the best indicator is that my sleep scores are relative stable and only dipping below 75 4 times since returning.

Vo2Max/RHR: My average resting heart rate was 49. My Vo2Max according to Garmin is now slightly above 52.

LDL: After the sudden increase while travelling my LDL has dropped back down to normal levels. I’d like to get it down below 2 mmol/L.

PhenoAge: I’m going to start tracking PhenoAge more regularly as part of these quarterly posts, so here is the first one. Lots to improve on! I calculated one using my data from 01-2024 and it was almost 11 years difference, so it seems like I’m going backwards.

Focus For Next Quarter

I think the main focus for next quarter will be relatively similar to this one. I am unlikely to change my supplements that much, and I think my main goal should remain to add muscle. One other potential area of exploration might be to look at stress levels, and see if I can correlate Garmin’s stress score with other events. For example, here is my stress graph for today, where I wasn’t able to run or go to the gym. My average “stress score” is 26", which is higher than my quarterly average of 21.

This becomes obvious when compared to my score from a few days ago, when I did 4x4s in the morning and a hard(ish) leg day at lunch.

I need to figure out how to better overlay my daily activities before I can solve this one, so I might explore this over the next quarter.