One of my major goals for this year was to figure out an effective way to get rid of my visceral fat. I wrote in the past about many things that I’ve tried. By far, the most effective thing for me appears to be extreme fasting. Even though this is highly effective, it comes at a cost. The longer I fast, the more muscle I lose. This isn’t an acceptable solution to me so when I discovered the Prolon fasting mimicking program, which claims to provide all the benefits of a water fast while preserving muscle, I couldn’t wait to try it.

The Prolon Fasting Mimicking Program consists of a suite of products. For the purposes of this blog post, I will mostly be referring to the Prolon 5-Day Fasting Mimicking Program. I will be explicit at any point that I’m referring to another one of Prolon’s products.

The Prolon Fasting Mimicking Program is a patented system based on the research of Dr. Valter Longo. After decades of research, the company has put together a complete 5 day food program designed as a “Fasting Mimicking Diet” (FMD). The goal of an FMD is to allow you to eat a low calorie diet while staying below the threshold of nutrient sensing pathways that are upregulated while doing a water fast.

Prolon claims to provide the same benefits as a prolonged water fast. If you’re new to longer fasts, many people do this for the metabolic benefits and autophagy specifically. Losing non-lean body mass is just a nice added benefit. As mentioned, I’ve experienced the benefits of fasting before and didn’t really need to be convinced of that. I was most interested in getting the muscle preserving aspects of this program combined with the fasting benefits.

There are three main pathways that Prolon focuses on: IGF-1, mTOR and PKA. IGF-1 is primarily activated by protein (especially the amino acid leucine). IGF-1 and amino acids will also activate mTOR. PKA is activated by carbohydrates and to a lesser extent caffeine.

Everything you need for the Prolon FMD is provided in a single box. This box contains smaller boxes, one for each day of the program. There is a menu card inside that describes which pieces of each box you should consume when.

Each day’s box contains a mixture of soups, nut bars, ‘snacks’, herbal teas, a proprietary glycerol drink, supplements and herbal teas. Each day’s caloric content ranges from ~1100 calories on the first day to ~700 – 800 on subsequent days.

The Prolon 5 day program also comes with coach led guidance. There is an hour long meeting each day of the program (as well as one day before and one day after) for everyone who is currently participating in the program to ask questions and commiserate. Initially, I was going to skip this aspect of the program, but I was ultimately glad that I did as I did find value in it. I would highly recommend restructuring your schedule in order to take advantage of this. Even more so if you are new to extended fasting.

Each day, the coach would remind us to ‘live in the box’… essentially resist all temptation to consume anything not provided by the program. Many people were shocked by the lack of caffeine in the box. This was where one exception was allowed. If absolutely necessary, you could consume no more than 140mg of caffeine per day. I didn’t want to get involved in trying to measure this, so I just went forward and completely cutout caffeine for the week as well.

I’ll admit that I was initially very skeptical on the ‘preserve muscle mass’ claims. This grew even more as I researched the program and saw that it was completely ‘plant based’. The day before my cycle was supposed to start and I listened to the coach repeatedly tell us to abandon our workout plans during the week, I was completely convinced that this was not going to meet my expectations. In my past experience, continuing to work out at least at a lower level of intensity was the only thing that helped preserve muscle during longer fasts.

Despite this, I decided to ignore all of my past experience and follow the program to a T. Keeping in this spirit, I also abandoned all supplements for the week. I wanted no confounding variables skewing the results of this program.

I was initially surprised how high the calories on day 1 were. I was concerned that eating anything would make me want food more than just fasting would. In the first 2 days I was definitely feeling hunger, but that mostly went away by day 3. By day 4, I was really looking forward just to the ceremony of eating food that didn’t come out of one of the Prolon boxes, but I wouldn’t really say that I was ‘hungry’.

I was also shocked that the lack of caffeine really did not bother me. I’m pretty sure every other time I did extended fasting, I still had black coffee or green tea.

When day 6 rolled around, I still wasn’t really hungry. I really wanted to go out for a beer, but I kept with the coach’s suggestions… no alcohol, and still mostly plant based until dinner. As recommended, I broke my fast with one of Prolon’s Fasting bars. I find these to be quite good and have since incorporated them into my regular time restricted eating program. I prepared the program’s recommended meals to ease back into the world of eating for the rest of the day. The only deviation was to add (the coach allowable) skinless chicken breast to my dinner. I started working out again on this day as well.

So, the real question… did it work? There’s no question that I definitely felt the same way that I would if I were strictly water fasting. Anyone who’s done that before will recognize that feeling you get around day 3 of doing so and it was definitely present here.

Is Prolon ‘easier’ than a strict water fast? Probably, especially if it’s your first extended fast. Psychologically for me though, the temptation of eating just a little bit was rough at times. Olives never tasted so good! I was watching my biomarkers every day and saw noticeable improvements.

Each day of the fast, my resting heart rate, body temperature and breathes/min trended down. At the same time, my HRV trended up ward. Blood pressure also trended down, but went up to my normal range when I started eating again.

On day 7 was the only time I’ve ever seen my Oura stress resilience score go into the ‘Exceptional’ range. But what about the numbers that really matter?

Over the course of the program, I lost 1.4% body fat. The bulk of that actually being visceral fat. My water mass was raised by almost 2%. I was hydrating way more than usual since that was completely allowed (and required to get the proper amount of the glycerol drink in). Finally, my muscle mass was up .6%!

It’s been a few weeks, and although some of the body fat has come back, my muscle mass has been trending upward ever since. Prolon recommends that you start by doing 3 monthly sessions and then taper off to using the system quarterly. I am not planning on following this recommendation, but I think Prolon is worth doing on a somewhat regular basis. Since I tend to do an extended fast on a regular basis, I plan on doing more investigation into how to replicate the results I’ve seen on Prolon for future fasts.

One of my major goals for this year was to figure out an effective way to get rid of my visceral fat. I wrote in the past about many things that I’ve tried. By far, the most effective thing for me appears to be extreme fasting. Even though this is highly effective, it comes at a cost. The longer I fast, the more muscle I lose. This isn’t an acceptable solution to me so when I discovered the Prolon fasting mimicking program, which claims to provide all the benefits of a water fast while preserving muscle, I couldn’t wait to try it.

The Prolon Fasting Mimicking Program consists of a suite of products. For the purposes of this blog post, I will mostly be referring to the Prolon 5-Day Fasting Mimicking Program. I will be explicit at any point that I’m referring to another one of Prolon’s products.

The Prolon Fasting Mimicking Program is a patented system based on the research of Dr. Valter Longo. After decades of research, the company has put together a complete 5 day food program designed as a “Fasting Mimicking Diet” (FMD). The goal of an FMD is to allow you to eat a low calorie diet while staying below the threshold of nutrient sensing pathways that are upregulated while doing a water fast.

Prolon claims to provide the same benefits as a prolonged water fast. If you’re new to longer fasts, many people do this for the metabolic benefits and autophagy specifically. Losing non-lean body mass is just a nice added benefit. As mentioned, I’ve experienced the benefits of fasting before and didn’t really need to be convinced of that. I was most interested in getting the muscle preserving aspects of this program combined with the fasting benefits.

There are three main pathways that Prolon focuses on: IGF-1, mTOR and PKA. IGF-1 is primarily activated by protein (especially the amino acid leucine). IGF-1 and amino acids will also activate mTOR. PKA is activated by carbohydrates and to a lesser extent caffeine.

Everything you need for the Prolon FMD is provided in a single box. This box contains smaller boxes, one for each day of the program. There is a menu card inside that describes which pieces of each box you should consume when.

Each day’s box contains a mixture of soups, nut bars, ‘snacks’, herbal teas, a proprietary glycerol drink, supplements and herbal teas. Each day’s caloric content ranges from ~1100 calories on the first day to ~700 – 800 on subsequent days.

The Prolon 5 day program also comes with coach led guidance. There is an hour long meeting each day of the program (as well as one day before and one day after) for everyone who is currently participating in the program to ask questions and commiserate. Initially, I was going to skip this aspect of the program, but I was ultimately glad that I did as I did find value in it. I would highly recommend restructuring your schedule in order to take advantage of this. Even more so if you are new to extended fasting.

Each day, the coach would remind us to ‘live in the box’… essentially resist all temptation to consume anything not provided by the program. Many people were shocked by the lack of caffeine in the box. This was where one exception was allowed. If absolutely necessary, you could consume no more than 140mg of caffeine per day. I didn’t want to get involved in trying to measure this, so I just went forward and completely cutout caffeine for the week as well.

I’ll admit that I was initially very skeptical on the ‘preserve muscle mass’ claims. This grew even more as I researched the program and saw that it was completely ‘plant based’. The day before my cycle was supposed to start and I listened to the coach repeatedly tell us to abandon our workout plans during the week, I was completely convinced that this was not going to meet my expectations. In my past experience, continuing to work out at least at a lower level of intensity was the only thing that helped preserve muscle during longer fasts.

Despite this, I decided to ignore all of my past experience and follow the program to a T. Keeping in this spirit, I also abandoned all supplements for the week. I wanted no confounding variables skewing the results of this program.

I was initially surprised how high the calories on day 1 were. I was concerned that eating anything would make me want food more than just fasting would. In the first 2 days I was definitely feeling hunger, but that mostly went away by day 3. By day 4, I was really looking forward just to the ceremony of eating food that didn’t come out of one of the Prolon boxes, but I wouldn’t really say that I was ‘hungry’.

I was also shocked that the lack of caffeine really did not bother me. I’m pretty sure every other time I did extended fasting, I still had black coffee or green tea.

When day 6 rolled around, I still wasn’t really hungry. I really wanted to go out for a beer, but I kept with the coach’s suggestions… no alcohol, and still mostly plant based until dinner. As recommended, I broke my fast with one of Prolon’s Fasting bars. I find these to be quite good and have since incorporated them into my regular time restricted eating program. I prepared the program’s recommended meals to ease back into the world of eating for the rest of the day. The only deviation was to add (the coach allowable) skinless chicken breast to my dinner. I started working out again on this day as well.

So, the real question… did it work? There’s no question that I definitely felt the same way that I would if I were strictly water fasting. Anyone who’s done that before will recognize that feeling you get around day 3 of doing so and it was definitely present here.

Is Prolon ‘easier’ than a strict water fast? Probably, especially if it’s your first extended fast. Psychologically for me though, the temptation of eating just a little bit was rough at times. Olives never tasted so good! I was watching my biomarkers every day and saw noticeable improvements.

Each day of the fast, my resting heart rate, body temperature and breathes/min trended down. At the same time, my HRV trended up ward. Blood pressure also trended down, but went up to my normal range when I started eating again.

On day 7 was the only time I’ve ever seen my Oura stress resilience score go into the ‘Exceptional’ range. But what about the numbers that really matter?

Over the course of the program, I lost 1.4% body fat. The bulk of that actually being visceral fat. My water mass was raised by almost 2%. I was hydrating way more than usual since that was completely allowed (and required to get the proper amount of the glycerol drink in). Finally, my muscle mass was up .6%!

It’s been a few weeks, and although some of the body fat has come back, my muscle mass has been trending upward ever since. Prolon recommends that you start by doing 3 monthly sessions and then taper off to using the system quarterly. I am not planning on following this recommendation, but I think Prolon is worth doing on a somewhat regular basis. Since I tend to do an extended fast on a regular basis, I plan on doing more investigation into how to replicate the results I’ve seen on Prolon for future fasts.