My Experience with Fasting Mimicking Diet

Since I posted my experience on the Prolon Fasting Mimicking Diet (FMD) is , I had many questions on fasting. First of all, what is fasting? Common definition is the abstinence from all or some kind of foods. However, the biological definition of fasting is the switch from burning glucose for energy to burning fatty acids and ketones. FMD is not the same as Intermittent Fasting or Time Restricted Feeding. 

Types of Fasting Defined:

Time Restricted Feeding (TRF): Daily pattern of eating during a window of 8 hours or less

Intermittent Fasting (IF): Extended periods of time (16-48 hours) with very little or no energy intake alternating with intervals of normal eating.

Periodic Fasting (PF): 2-21 or more days broken up into periods of fasting or fasting mimicking diets.

The Prolon FMD program food provides some calorie – 1200 cal on day 1, then 800 cal daily from days 2–5. The “food” is plant based, low on protein, fats, with minimal amount of carbohydrates. This diet tricks the body into believing it is in a fasting state without the discomfort of true fasting. Why 5 days? Because this is just enough for the body to get the benefits of fasting, and any longer the body will starve and start to break down.

What are the benefits of fasting?

FMD promises to promote longevity by improving overall health, reduce excess fat, and promote regenerative and rejuvenating changes to the body, and helps maintain lean body mass.  Prolon FMD research also showed some interesting clinical outcomes. See this link:

So, being a skeptical pharmacist, I had to test out this product myself. And I convinced my spouse Olov to do this with me!  

Below is a recap of our journey with Prolon FMD. We started January 7th, 2019.

Day 1 – Why Am I Doing This? 

We opened our boxes of “food”. We really weren’t too sure how this is going to work out.  The little box marked Day 1 seemed rather skimpy.  We looked at each other and Olov asked “So why are we doing this?” I answered “More out of curiosity than trying to change body images. Check out the benefits chart!”  So with some hesitation, we started. 

We both had a black coffee and the little bar in the morning. That wasn’t too bad. The soup for lunch was actually kind of tasty, and the kale crackers were pretty decent too.  Of course, we drank a lot of water in between meals. We had soup again for dinner at 6PM, then felt my brain slowing down as I had a hard time getting through a simple Sudoku puzzle. Olov felt ok, and didn’t have any complaints.  Then 9:30pm came, my usual bedtime, I felt really, really hungry. It was difficult to fall asleep so hungry.  Apparently Olov had no issues falling asleep (see my eyes rolling here?). Then 11PM came, I was finally tired enough that I fell asleep.

Day 2 – I Need Sleep!

This morning I woke up feeling a little tired. I didn’t sleep too well because I was pretty hungry last night and had trouble falling asleep.  We both though we would be ravenously hungry, but nope. We were just fine. I decided to do a blood glucose test to see where I am at. 4.2, perfectly normal. I guess my pancreas and liver are working just fine. 

We started out with a cup of black coffee, but It wasn’t until an hour later that I started feeling hungry, so I had my breakfast bar. I am thankful this program allows black coffee, however I’ve dialed it back from two cups to one cup daily as I found the second up yesterday made me feel jittery.  Prolon recommends that while on this program, avoid vigorous exercises. So an easy walk my dog Cooper would be my exercise for the 5 days. 

I felt slightly hungry throughout the day. The food supplied helped to suppress hunger for about 2 hours. After that it’s sheer will power. I also realized how often I reach for snacks. It was hard to keep my hands out of the nuts jar. But I did it!  Olov and I also talked about how much more water we drink, and it felt good to be fully hydrated. We agreed we would definitely continue to drink more water after the 5 days. 

Doing paper work can be boring. But today I plowed through them and stayed focused. This felt similar to the focus I experienced while on ketogenic diet a while back. I wonder if ketosis is kicking in? Olov on the other hand felt sluggish today, and this is normal according to the information pamphlet. 

Day 3 – A Little Blue?

Interesting when food is scarce, even a little bar, freeze dried soups and a few olives can taste so good! I savored my breakfast bar over 10 minutes today, and it dawned on me that I usually eat way too fast.

We were warned that Day 3 would be the worst day. I felt really great in the morning and didn’t think much of it.  I worked on my daily tasks just the same. Around 4pm, I started feeling really low in energy and down in mood. As I still have one more networking event to attend in the evening, I decided to just suck it up and go. I made it through, but throughout the event I felt really down. 

Thinking through this issue, I figured I may be missing my supplements. Specifically the one I take for thyroid support. I’ve put all my supplements aside for this diet because this diet supplies a multivitamin. But this is not the same as what I use for thyroid support. So tomorrow I will star taking my thyroid support again. There is a difference between not having energy and feeling down.  I don’t mind feeling tired, but I don’t want to feel blue.  Olov on the other hand did not report any issues, and seems to be handling his fasting just fine. 

Day 4 – Deep Sleep and Lucid Dreams?

I slept well last night with dreams! I know this shouldn’t be shocking. But I don’t recall having dreams for a long time. I woke up feeling refreshed and ready to go. No hunger, no cravings. According to my Garmin watch, I was in deep sleep for 3.75 hours. Wow, usually my deep sleep ranges from 2 to 3 hours. Olov said he slept soundly as well. There is something magical about going to bed in a slightly hungry state. 

Overall we both felt more energetic today with better mental focus. This helped me to accomplish more, checking off my tasks rather proficiently! Olov even went out and did a lot of yard work. The program said no vigorous exercise, yet he trimmed of our cedar hedging. That’s heavy work! He jokingly said that he had more “reserve fat”, and he is happy to be burning them. The scale showed that he had lost 7 lbs since day 1! I didn’t weigh myself because I wasn’t interested in losing weight. But I should have. So weighing myself now and no surprise, I came in slightly under the norm.

Day 5 – Easy Does It

This was by far the easiest day to go through. We both felt great with no side effects. Waking up in the morning we both felt energetic and din’t feel hungry at all. Oddly, neither of us missed food.  And even stranger is the sense of liberation from having to eat 3 square meals plus snacks.  

Biochemistry wise, morning fasting blood sugar is down to 4.1. Urine pH is slightly higher at 8. This is not surprising as autophagy*(see more on this below) should start on day 4 through 5, and higher urine pH usually indicates breaking down of tissues. Vital signs still good. Resting hear rate was 52, BP 106/68 (again, this is my normal). 

Overall, we both felt great the whole day and had no issues dealing with slight sensation of hunger. In fact, I am not sure how I managed stuff so much food into this body before.

*Autophagy (“self-eating”) is a process your body undergoes to clean out damaged cells and regenerate new ones. A protein called p62 activates to induce autophagy.  This process is key to anti-aging. As we get older, our cells accumulate a variety of dead organelles, damaged proteins, and oxidized particles that age us and cause diseases. Autophagy is a way our body gets rid of these faulty parts and defends itself naturally against aging and diseases.

Wow, now that the 5 day fasting program is done. Now what? 

Day 6: Break-fast! 

Nope, we did not dive right into eggs and bacon this morning. Oddly, I did not crave a sumptuous breakfast like I thought I would either. 

Prolon recommends that you ease your body back into eating and slowly introduce solid foods over the next few days. 

So my first meal? Coffee with coconut milk and home made kefir. For lunch, it’s home made pea soup. Dinner was shrimp salad, and more salad. Oh I miss my greens! I noticed that I felt full after just a small amount of food. Portion wise it was about half of what I would normally eat. 

Day 7 – Back to Routine? Not so fast!

I went for a 10K walk instead of running this morning.  Given that I haven’t fed my body properly over the past week, I thought I should just take it easy. The walk was good decision because I wouldn’t have had enough energy to run. I got home after the walk and had a full lunch….Now I understand why the company suggested easing back into eating. I felt stuffed and uncomfortable.  It went away eventually, but just to warn you in case you want to do this program. Small Portions!  Other than this, I still felt great. 


A month has gone by since our fasting experiment.

Olov informed me today that he’s lost a total of 10 lbs. to date, much better than results shown above. Pretty impressive, right?  Of course it really helped that we stuck to what we learned during this experiment.

More importantly, this experiment helped us to see how we can improve our eating habits: 

  1. Drink more water!  
  2. We both felt that not having so much food in our stomach at bedtime helped us to sleep better, so we’ve decided from now on, we will try to eat our main meal at lunch instead of late in the night.   
  3. I have learned not to snack so much.  Much of my snacking comes from emotional eating associated with boredom or stress. When I kept myself busy, eating doesn’t even enter my mind. Many occasions during this fast I wanted to reach for a snack, not because I was hungry, but out of habit! 
  4. We’ve also committed to getting active. Exercise (especially HIIT), is another way to boost autophagy, or cellular renewal. And did you know that exercise is the best way to increase BDNF – Brain Derived Neurotrophic Factor, kind of like growth hormone for your brain? 

My skeptical mind has concluded that FMD is beneficial. As I mentioned, I didn’t intend this to be a weight loss program. Rather, I wanted to see if I would feel better, and if my biochemistry would improve. And yes, it did. My A1C lowered from 5.6 to 5.2, and my cholesterol also lowered slightly.

We will do this again later in February. For Olov, he found his weight loss to be encouraging and wants to see if he can lose more weight. For me, I’d like to see if I can lower my A1C further to under 5, which is what I was at when I was in my 30s. This is what I’d call Anti-Aging Medicine!


2 thoughts on “My Experience with Fasting Mimicking Diet

  1. Very interesting experiment, Amy & Olov, thanks for this.

    I am making a DETERMINED effort to lose weight and it turns out I have been doing some of what you suggest here.

    Even better, you have given me a few extra ideas that I’m gonna try!

    Thanks again,

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