What Is The Prolon Fasting Mimicking Diet, And Should You Try It?

What Is The Prolon Fasting Mimicking Diet, And Should You Try It?

Prolon Fasting Mimicking Diet

Soooo many people have asked me to do a Fasting Mimicking Diet review. The FMD is by a company named Prolon. 

I’m lucky to have a lovely colleague who worked for Prolon, who was nice enough to discuss the Fasting Mimicking Diet with me and give me some of the important deets. 


What is the Fasting Mimicking Diet?

The Fasting Mimicking Diet was developed by Valter Longo, an Italian biologist (not a medical doctor, FYI) and director of the Longevity Institute at the University of Southern California. 


Longo’s area of research is, as you probably would guess, longevity, and the main goal of the Fasting Mimicking Diet is to attenuate aging, decrease inflammation, and improve overall health. 


It wasn’t developed as a weight loss diet per se, but weight loss is one of the common effects of the FMD, and it’s one of the reasons why many people do this program.

Unlike other fasting diets where you consume nothing, the FMD is supposed to trick the body into believing that it’s not receiving food for a certain number of days per month, and in doing that, activate anti-aging pathways. 


On the Fasting Mimicking Diet, you do eat, but not very much. We’ll get into that in a second. 

Apparently, Longo developed this diet as an alternative to water fasting, which is notoriously tough to follow (and, IMO, unnecessary for health).


The idea behind fasting is that while they aren’t receiving nourishment, cells apparently ramp up their autophagy process, which is when they eat and destroy components that aren’t necessary or that are potentially harmful. 

Autophagy also appears to renew healthy cells. 

It’s like taking out the cellular garbage, and replacing it with shiny new stuff, if you will. 

We know that autophagy is a normal process, and it happens in all of us. But it is thought that fasting increases the rate at which it occurs.


I was offered a trial of the Fasting Mimicking Diet to try, but I declined.

This is why:


I have a tendency to become obsessive with counting/diets/food things. I suspected that fasting for five days would be very triggering and a really bad idea for me. 

In fact, I don’t recommend this sort of diet for anyone with a history of eating disorders or anyone who becomes obsessive with food. 

The second reason is that I didn’t want my kids to see me doing it. 


As the mother of 11 year old and 13 year old girls, I can’t think of a worse example to set than fasting for five days in front of my daughters. 

I know some of you will believe that doing the FMD would set an example of ‘self-care’ for my kids, but I don’t see it that way.

For me to go from encouraging them to love food and eating in front of them and with them, to essentially starving myself, would be unacceptable, confusing, and potentially dangerous. 

Even if I told them it was for ‘health’ and not for weight, it goes against all of my ethics. 


The Fasting Mimicking Diet food.

Initially, the FMD is meant to be done once a month 3 months, for five days at a time.


When you go onto the FMD, you’ll receive all the food you’ll need for the five days, neatly packaged and delivered to your door. 

The five days are a very low calorie, pre-packaged regimen – things like Prolon-branded bars, soups, olives, tea, and glycerol-based drinks that are supposed to keep you full. 


On 770 calories a day (1200 on day 1), that might be an issue. 


It’s all very prescriptive – you’re not allowed to mix food from different days, and you must eat the food you’re given. 

After the five days, there’s  a transition day of soups and light meals before resuming your normal diet on the 7th day.


Interestingly, Prolon says that you should ‘avoid binging’ after your fast. 


After the first 3-month cycle is complete, Prolon recommends doing the cycle 1-2 times a year.

That means that if you do it twice a year, that’s 6 months out of 12 that you’ll be in the cycle. 


The research.

The research on prolonged fasting in humans is pretty sparse. 


In lab animals, severe caloric restriction seems to increase lifespan. We don’t, however, know how this affects people, because 

  1. it’s unethical to starve people and 
  2. nobody willingly submits themselves to a starvation diet unless they have circumstances that would preclude them from participating in a study like this anyhow.

The Fasting Mimicking Diet was recently tested in a group of breast cancer patients receiving chemotherapy, and similar to recent studies on cancer patients and the keto diet, the FMD study suggested that fasting may increase chemotherapy effectiveness and decrease side effects from the treatment. 


A 2017 study – the only one on the Prolon website under the ‘research’ tab – had participants do three cycles of the Fasting Mimicking Diet – one week every month for three months.

The results suggested that compared to the control group, those who completed the FMD cycles reduced body weight, blood pressure, and IGF-1, which is a hormone that is associated with aging and cancer (but also, with normal growth and development). 

25% of the participants dropped out during the course of this research, which is an extremely large number. 

When a quarter of your participants drop out mid-study, there could be a lot of reasons – one usually being that the regimen was too difficult to follow.


As far as the results gained from the FMD, there’s a lot of ‘allegedly’ going on here.

Allegedly, the diet may lengthen the life of humans.

Allegedly, the diet helps decrease the rate at which telomeres shorten (which is part of the aging process).

Allegedly, autophagy rids us of ‘bad’ cells, and rejuvenates our cells.

Allegedly, it ‘cleanses’ us on a cellular level. 

Do a lot of unknowns mean that the eventual outcome will be bad?

Not necessarily. It just means that we don’t know. And while there is research being done on the FMD, we probably won’t know the results for quite a while. 


If you spend one week a month eating far less than what is normal for you, and you resume your normal diet afterwards, simple math says that you’ll probably lose weight because of the calorie deficit that results. It’s not complicated.

But again, the FMD wasn’t developed for weight loss. It’s more for longevity and overall health.

And as far as longevity, as I mentioned before, there are no long-term human studies on Prolon. 

We can extrapolate evidence from animal studies in this realm, but I wouldn’t. We aren’t animals.

There are a lot of unanswered questions, at least in my mind:

The FMD may be easier to stick to than 5 days without food at all, but why do we want to put ourselves through either of those things? Is it really necessary?

Is the Fasting Mimicking Diet more effective for health than time-restricting eating or the keto diet? We don’t know. There is no research comparing the FMD to other diets.

Does it work better than a low calorie diet? Are the benefits from the diet, or from the weight loss? Again, we don’t know.

(Keep in mind, I don’t recommend diets at all).


The Fasting Mimicking Diet, in short.

This whole thing leaves me with the question: to what end do the changes seen with the FMD extend life or improve health? What do we gain from doing this fast, and what can we lose?


I guess everyone needs to answer that for themselves.


I always have the mindset of, do we need to hack everything? Can’t I eat a nourishing diet, move my body, be happy, and have around the same effects that this diet will give me?

Maybe not, but I’m happy to leave that to chance.



Interesting in intermittent fasting? Read my review of it here, first.