Comparing Fasting Types: ProLon’s Fasting Mimicking Diet vs Water

*Updated June, 2020

Don’t let the term FASTING scare you.  It’s completely natural.

If you ask anyone who’s ever done a fast properly, the one thing you will undoubtedly hear is, “I just did a fast and I feel great!”

Whenever I merely mention the word “fasting” to someone who’s interested in weight loss or improving their health, I can feel a palpable discomfort.

I may detect a slight grimace or widening of the eyes or maybe a low groan.  It’s not like I just walk around randomly talking about fasting.  But when people ask me which about diets I think are the best, I will always bring up Intermittent Fasting as a good option.

After all, what is a “good diet?”  One that helps you lose weight (if you’re overweight) and gives you long term health benefits, right?

The research on fasting so far shows many benefits for health, weight loss and even longevity.  So, yes, I practice intermittent fasting as well.

I do IF a fews days  a week for 16 – 20 hours and a couple of days at 12 – 14 hours.  If you’re not sure what IF is, it’s going at least 12 hours and up to a few days without food.  Technically, we refer to going less than 24-hours without food as “Time Restricted Eating” (TRE).  The goal is to limit your feeding window.  So on a 16 hour fast or time restricted eating window, for example, there are 8 hours in the day where you can eat your meals.

There are all kinds of routines you can follow for IF and TRE.

I think too many people have been sold on the “eat frequent small meals a day” hype.  I’ve written and talked about this before.  In short, I’m not a fan of it.  It’s not natural.

Our bodies weren’t designed to eat all day long. It’s been less than 100 years since we’ve had refrigeration. Before that, we never had access to food 24/7.

We were designed to weather bouts of famine.  That’s why the body has fat cells to begin with!  It’s where we store our extra energy for times when access to food is scant.

Nothing bad will happen if you go at least a good 12 hours without food most days of the week, like from dinner to, ahem… break-fast.

As a matter of fact, 12 hour fasts may even be one of the secrets to longevity.

This is one of the main tips Valter Longo, PhD gives in his book, “The Longevity Diet.” Dr. Longo is a professor of Gerontology and the Director of the USC Longevity Institute.  His decades of research and published studies on longevity lead him to believe there is a way to mimic the benefits of fasting with what he calls the “Fasting Mimicking Diet.”

I’ll get to more of the FMD in a minute.

First, let’s look at what the benefits are of doing short term fasts.

Intermittent fasts can range anywhere from 12 hours a day to several days or even 2 weeks at a time.  It would be wise to do anything longer than 3 to 5 days under medical supervision.  (When you get to the videos below, you’ll see how my partner Jim does on a 12-day water only fast!)

According to Longo, it takes about 3 days of being in a fasted state for the body to start regenerating stem cells.  To me, cellular regeneration is the ultimate jackpot!  But even shorter, intermittent fasts have worthwhile benefits.

Benefits of Intermittent Fasting:

  • More mental clarity and better concentration. Seems like all you can think about is food, but hunger comes in short waves.  Once it passes, your mind is more clear.  There are super high performers know to have eating windows of only 1 to 4 hours and they fast the rest of the day.
  • Fat loss. We used to think fasting made you lose muscle mass too.  It’s true, depending on how long you fast, there will be some.  Most of that will really just be water weight, so don’t worry.  You lose much more fat than muscle because that is what fat cells are for… storing energy when food is scarce.  Your body doesn’t want to burn muscle, so it will be burning body fat when it runs out of glycogen (the stored form of glucose or sugar from carbohydrates).
  • Lower blood sugar.  Excess sugar in the blood is for most people the number one cause of fat gain.
  • Reversing insulin resistance and type 2 diabetes. Ketogenic diets, exercise and certain fasts are also useful for this.
  • Increased energy. Sounds counterintuitive, but when you get into ketosis, your body is using ketones for energy.  This also is why you have more mental clarity.
  • Increased levels of human growth hormone. HGH drops as we age, and it also drops when we eat.  However, when we’re in a fasted state, like sleeping, or not eating on purpose, it increases.  Like all body builders and athletes know, the muscles grow while you’re resting.
  • Lower cholesterol. Particularly the bad kind which are the small, dense LDL particles.
  • Reduced inflammation. Makes sense.  If you’re not eating anything, there’s nothing coming in that can cause an inflammatory response.
  • Stimulating autophagy. This is a big win!  Autophagy is the body’s way of removing the damaged parts cells by basically eating itself and recycling the good bits to be used in new cells.

Time Restricted Eating may help you live longer

In case you’ve heard of the term, there is also such a thing as “time restricted feeding” which is a type of IF (and deserves it’s own blog post).

TRF is when you pick a window for eating your meals, for example, 6am to 6pm and works optimally during the day time.

Not eating late at night works great with our internal time clocks (circadian rhythm) and has been shown to help in weight loss, reverse metabolic diseases like type 2 diabetes and manage cholesterol.

Restricting your meals to a window of no more than 12-13 hours is what Longo suggests is a factor in longevity.

IF, on the other hand, is typically considered to be 16 hours of fasting or longer.

Fasting with food?  Huh?

Now if only there were a way to package up the benefits of fasting and put it in a box…. Oh, wait a minute, there is!

Dr. Longo developed a kit containing all the foods you need to do a Fasting Mimicking Diet. The product is called ProLon (short for pro longevity) and I tried it.  ProLon has bragging rights in that it is the first and only diet program to go through a clinical trial at the University of Southern California and is also patented for its anti-aging effects.

You may now be cocking your head to one side, wondering, hmm, how can you eat food and be fasting at the same time?  Good question. I sat down with Dr. Longo’s business partner, Joseph Antoun, CEO L-Nutra Inc. (the parent company to ProLon) for an interview and asked.

Antoun explained the products were carefully formulated to “mimic the positive health effects of fasting while compensating for the negative effects of it,”  meaning, starving.  He says with water only, you may feel faint, weak and not be able to work.

Each day the calories fall between approximately 800 and 1,100 calories.  A typical fasting diet is more like 500 to 600 calories.  The secret, according to Antoun, lies in the formulation.  The ingredients in the foods will nourish the body, but won’t trigger the nutrient sensing pathways, PKA (protein kinase A), Ras and mTOR (mammalian target of rapamycin).

“The food goes into the blood but it won’t trigger the sensors on the cell so that the cell is not in a pro-growth mode.”  In other words, the food enters your body in stealth mode, therefore your body doesn’t recognize the fact that it’s eating food.


It takes three days to really get into the big benefits, like stem cell regeneration.  This is true of any fast.  And this is also approximately how long it takes to get into ketosis where your body uses fat for fuel.  But this is another topic.

Dr. Longo’s goal with the food supplied, is that getting into a fasted state should be a more comfortable transition.

Click here to try the ProLon FMD and get 10% off your order.


Why does it take three days?

Antoun explains it like this:  the first 2 days of a fast, your body is just waiting for you to eat.  By the third day it senses something is up and starts to worry that it might die.  After all, if you faint, you might get eaten by a lion (if you live in Africa or a zoo).  If you can’t think, you can’t figure out a way to get food and, if you can’t get up and run away from danger, you might become dinner.

So the body, smart as it is, does what any intelligent business owner would do if they were running out of funds.  By days 4 and 5, it starts tightening the budget and letting some people go that are dead weight.  These are the cells that are old, damaged and not doing their jobs anymore.  The body disposes of them like henchmen in a Sopranos episode.

Programmed cellular death is known as apoptosis. The cells not ready to totally die, get to do a little self-cannibalism and save any good bits for recycling.  This process is known as autophagy. Once the body has cleared out the garbage and recycled what it can re-use, it calls on the stem cells who are waiting in the wings, to make replacement cells.

“This cellular rejuvenation is the essence of our patent and the essence of how we want to intervene to reverse the course of disease.”  If there’s one thing that separates Longo’s FMD and L-Nutra from other products on the market, it’s that, “we’re the only diet that creates enough stress in the body to take cellular action, not only metabolic action.”

They back up their claims with a clinical trial on 71 people funded by USC and National Institutes of Health.  The study showed the ProLon diet reduced the participants’ risks for cancer, diabetes, heart disease and other age-related diseases, according to the findings published February 15th, 2017 in Science Translational Medicine.  The diet also caused the added bonus of weight loss without muscle loss.

The program is designed to be used for three consecutive months for 5 days out of each month.  But Dr. Longo says in his book, for people who are healthy, they can get benefits in just doing the program twice a year.

As for the study participants who were considered most “at risk,” because they came in with high levels of IGF-1, cholesterol, blood pressure or blood sugar levels, made significant progress toward better health.

Here are the cliff notes on the what the FMD has the potential to do.

Benefits of Fasting Mimicking Diets:

  • Decrease weight and body fat
  • Stem cell regeneration
  • Maintain glucose (blood sugar) at healthy levels
  • Maintain C reactive protein (a marker for inflammation) at healthy levels
  • Maintain triglycerides at healthy levels
  • Maintain blood pressure at healthy levels
  • Maintain healthy levels of bone density
  • Impact in IGF-1 (a marker for aging)
  • Maintain insulin resistance at healthy levels
  • Maintain cholesterol at healthy levels
  • Decrease visceral fat (the most dangerous kind found around the vital organs)

Before it was tested on humans, it was tested on mice.  Longo says the mice in the study only fasted twice a month for four days and lived longer and had only about half of the cancers. When they did develop cancer, it was later in life.   They also had better cognitive performance, less inflammation, and  lost fat specifically in the abdomen.

Dr. Longo concedes, “larger FDA studies are necessary to confirm its effects on disease prevention and treatment,” but thousands of health care providers are recommending the diet to their patients now.

Strict fasting, using water only, has been around for as long as we have – whether we wanted to do it or not.  You may have done it for religious reasons or medical reasons.  If so, you know how difficult it can be.  So would you rather do a Fasting Mimicking Diet or a strict water fast to get all those benefits?

I took off from work and went to the desert with my partner Jim so we could compare.  Jim did the water only fast and I tried ProLon which costs about $200 for the 5 day kit containing all you need to eat for 5 days.  That’s $40 a day which, in many cities is what you could easily spend eating lunch and dinner out.

If you want to try it for yourself – you’ve got nothing to lose but some body fat and worn out, dying cells – click here, then enter my discount code:


Here’s Our Video Diary:











Of course not everyone should do a fast.  ProLon will give you a short medical screening first before you order it and put you on the phone with a Registered Dietician to make sure you’re good to go.

You Should Not Fast If You Are:

  • Underweight (BMI < 18.5)
  • Pregnant – your baby needs to be fed even if you don’t.
  • Breastfeeding – your baby needs that milk to have nutrients!
  • A child under 18 – calm down, you still may not be full grown yet.  However, talk to your doctor about possibly using ProLon if you think you need it.

You Need Medical Supervision If:

  • If you have type 1 or type 2 diabetes
  • If you take prescription medication.
  • If you have gout or high uric acid.


Disclaimer:  Some of the links above may contain affiliate codes meaning, I may receive a commission at no cost to you.  You actually receive a discount.  I do ProLon and IF regularly.  On all my blogs and posts, I only recommend products I believe and use personally.

Jill Brown
Jill Brown
Hi, I'm JillI am a Los Angeles based Fitness + Nutrition Coach. With 20+ years of experience in teaching, training and continuing my education, I have transformed thousands of lives through fitness and healthy lifestyle changes.