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ProLon Diet: A Skeptic’s Review of the 5-Day Fast

I’m not a fan of diets or cleanses (I think the body does this naturally). However, over the last year, I put on some weight despite regular workouts and clean eating. After completing two rounds of this fasting program, I feel confident to share my ProLon diet review, opinions, and results with you.

This post contains affiliate links. See my disclosure policy for more information. Some products were gifted to me but all opinions are my own.

What is Prolon?

Prolon is a five-day mimicking fast diet where your body gets the benefits of traditional water fasts but you get to eat actual food. Sounds good, right? 

It’s a longevity diet focused on cellular renewal and metabolic health. I’m in my late 40’s, likely in the midst of perimenopause. The diet also helps to target belly fat (more on that later). With my metabolism feeling all out of whack, I was excited to get started.

Although weight loss is not the goal but rather one of the side effects of the fast, most people will lose some weight due to the calorie restriction. The ultimate goal is autophagy, something I knew nothing about when I started the program.

I’ve known about ProLon for years. This low-calorie diet had become pretty popular in New York and many of my friends routinely used it. I had even watched a Goop episode about it where Gwyneth Paltrow and her team tried ProLon. Still, I had my reservations.

Who Created ProLon? 

Dr. Valter Longo, the director of the Longevity Institute at the University of Southern California and in Milan, Italy, created Prolon FMD (fasting-mimicking diet) based upon decades of scientific research. Dr. Longo based much of the program on the Blue Zones.

He authored the book The Longevity Diet. Interestingly, he donates profits to his charitable foundation, focused on helping those with serious diseases live healthier lives.

How Much Does the ProLon Fast Cost? 

​I’ll admit, at first, I thought that ProLon was expensive. Now that I see everything you get for the price, I’ve changed my mind for two reasons:

1. Food

First, everything you will eat for the week is included in your kit. You get a 5-day meal kit for $190 that includes all your soups, teas, bars, snacks, and supplements. Use promo code MYPURSESTRINGS to save 15% off your order. So, if you think about it, ProLon costs a little more than $30 per day.

Most people choose to do at least 3 to 4 consecutive rounds like I did so you can save more by signing up for Subscribe & Save or ordering a two-box bundle.

ProLon Fasting Nutrition Program -The 5-Day Fast With Food – Prolon FMD

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2. Coaching Call

I didn’t even know this was included when I signed up (and actually missed the first day). Every morning at 11 am EST, you can participate in a Zoom call with a ProLon registered dietitian (available on replay). This was my favorite part of the program.

There is also an active Facebook group called FASTNATION. I will caveat, while there is helpful information on there and ProLon representatives do jump on, there is also a good amount of speculation and sometimes incorrect advice.

What Foods are Included in ProLon? 

prolon day 3 sampling of foods including soup packets, supplements, bars and drinks

Each box contains food for that particular day:

  • Day 1: Transforming to a Fasting State (benefits that promote fat burning & cellular preparation)
  • Day 2: Fat Burning & Ketogenesis (benefits that promote fat burning & ketogenesis initiation)
  • Day 3: Autophagy Cleanup State (benefits that promote ketone production & cellular cleanup)
  • Day 4: Cellular Renewal (benefits that promote cellular renewal & fat burning)
  • Day 5: Renewal & Change (benefits that promote cellular renewal)

If you don’t like soup, tea, or bars, then ProLon is not for you. I happen to like all three.

Your order comes in a large box, filled with smaller boxes labeled by day, Day 1 to 5. Each box includes a sampling of powdered soup, herbal tea, bars, crackers, olives, supplements, and a specially formulated energy drink solution.

You can change the order of what you eat throughout the day but cannot switch food out from another day. You can see the daily meal program breakdown below.

prolon daily meal program breakfast lunch afternoon dinner


You start the day with a cup of tea and a nut bar. Surprisingly, these L-bars contain very little protein. On some days, you can have an L-Bar Choco-Crisp bar for dessert.


Each day you have spearmint tea and lemon spearmint herbal teas to drink. Some days, you also have hibiscus tea packets meant for the L-Drink.


On Days 2 through 5, you measure out the included L-Drink to a 32-ounce bottle with water. To determine how much of it to use, you need to mark off your weight on the bottle and pour from the top until you reach your individualized measurement. Sip it slowly throughout the day. It tastes fine alone but I liked adding the hibiscus tea bag to it. 

The purpose of the L-Drink is to prevent muscle loss and protein we do have. While it’s tempting to save the L-Drink, you must throw out whatever you have left over in the bottle each day.


I received the newest soup flavors, the Gen 3 box:

  • Red Bell Pepper and Onion (my least favorite)
  • Green Pea and Chives
  • Lentil Curry
  • Chickpea & Leeks
  • Carrot Ginger

Variety 2 Soups include: 

  • Butternut Squash
  • Black Bean
  • Butternut Squash with Quinoa
  • Spinach with White Bean 
  • Tomato

Original Variety 1 Soups which I did not try include these flavors: 

  • Minestrone
  • Tomato
  • Mushroom
  • Vegetable
  • Minestrone Quinoa
prolon lentil soup and olives

​The soups contained about 100 to 120 calories. They arrive powdered and require no prep other than heating water and mixing it.


A few times during the week, you get a small packet consisting of five kale crackers totaling 180 calories. These are a welcome addition as it’s nice to have something with crunch. They’re tasty. I always either ate half at lunch and saved the other half for dinner, or saved them all for dinnertime.


I happen to love olives, although I didn’t until I turned 25. If you don’t like olives, see if you can mash them up into your soup or tolerate them. You want the healthy fats in these olives to suppress your appetite and fill you up.


There are two supplements in the box: 

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What are the Major Ingredients in the Foods? 

You can find the full list of ingredients for each product here but the soups all contain rice flour and most of the bars (and some soups) contain chicory root fiber. 

prolon stack of crackers on white plate, red hibiscus tea l-drink in bottle and peppermint lemon tea in mug

Who Should Not Do ProLon?

Of course, check with your physician before starting any diet plan but ProLon does not want you to do the program if you are:

  • pregnant
  • breastfeeding
  • have an eating disorder
  • under the age of 18 or over the age of 70
  • underweight 
  • have dietary restrictions including allergies to nuts, celeriac/celery, oats, or sesame, or any other ingredients
  • ill ( fever, cough, diarrhea, signs of an active infection, are at risk for recurrent infection)
  • protein deficient or malnourished
  • someone with medical conditions such as diabetes (types 1 or 2), cancer, congestive heart failure, or a history of fainting (unless you are under a doctor’s supervision)

How Often Should You Do ProLon?

I appreciate that ProLon explicitly states that this program should not be overused. You must wait at least 25 days after your first round ends to start round 2.

According to their clinical studies, they recommend for most people, three to four rounds on consecutive months to achieve the full benefits of metabolic health, longevity, and healthy aging. After that, you should do it as needed, usually one to two times per year or as prescribed by your medical doctor. Some people choose to do ProLon monthly until they achieve their individual health goals.

One-Day Reset

If you want to reset any time, ProLon sells a one-day reset box. I have not tried it yet but I’m sure I will at some point. The 1-Day Kit is meant to be used between rounds of ProLon, so you can absolutely add a Reset in between rounds of ProLon. 

ProLon claims there are several benefits to completing their fast. Here are some of them: 

Benefits of Completing Prolon

How Much Weight Should You Expect to Lose from the ProLon Fast

In clinical trials, weight loss from just one cycle of ProLon was approximately 5 pounds and waist circumference was reduced by 1 inch, but results were more significant and were better retained after three cycles.

You may continue to lose weight on Days 6 to 10 as I did. Remember, losing a small amount of weight each round is the best to sustain weight loss. The goal is to keep off half the weight you lose.

​Is ProLon a Keto Diet? 

No. Although your body goes in and out of ketosis, ProLon does not keep you in a Keto state. 

Is ProLon a form of Intermittent Fasting? 

While I decided to fast during it until around 11 am, keeping to a 16:8 interval, not everyone does this. I chose to do it to reduce my hunger throughout the day and found I liked it. I’ve tried intermittent fasting in the past with mixed results but it seems to be working for me. You can eat whenever you feel hungry. 

Further, the ProLon Fasting Mimicking Diet plan does just that: you get the health benefits of fasting without having to actually do so.

Can You Work Out? 

It’s totally individualized. During both rounds, I limited my workouts based on the coach’s instruction. I did some core workouts and walks. Simply put, you don’t have enough protein or calories to fuel you through a workout so strenuous exercise is not advised. 

My Experience with Prolon

I did two rounds of Prolon, the first in mid-March of 2023 and the next one month later. I plan to do a third round at the end of May.

​Round 1

Day 0 is a prep day. Since this is a plant-based diet and I’m a vegetarian and fairly healthy eater, I didn’t do any preparation. But you might want to take it easy on this day.

Day 1 is a good amount of food, 1100 calories. Days 2 through 5 drop to about 750 calories. Day 6 is a transition day. The program has technically ended but you want to ease your body back into a normal diet.

On Day 1, I felt completely fine and had an adequate amount of food. I wasn’t very hungry on Day 2 but woke up feeling unsatisfied on Day 3 and quickly noticed the drop in calories throughout the day but my energy was still up. On Days 4 and 5, I wasn’t even hungry for lunch.

My favorite soups were the Green Pea & Chives and Chickpea & Leeks.

I did not enjoy the NR-1 supplements. I burped up the taste of it hours later and it seemed fishy to me although it’s made of only vegetables.

Round 2

The second time around, five weeks later, was much easier. Since the end of Round 1, I had continued with intermittent fasting, only drinking black coffee. Every morning at 11 am, I would have a Fast Bar and a light lunch. I tried to eliminate carbs and dairy and follow more of a Mediterranean diet, actually the MIND diet. 

I was barely hungry during this round. One day, I realized I had skipped my lunch soup entirely. 

I slept well, did not exercise other than long walks, and felt great. I plan to do Round 3. 

ProLon Fast Bars or Fasting Shakes

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My Results with Prolon

At the end of Round 1, I continued to lose weight for a few days until I reached the 5-pound mark and saw the biggest results in my tummy, where I seem to hold onto fat. 

Despite a vacation to Mexico between rounds 1 and 2, where I ate and drank everything, including desserts multiple days, I kept the weight off.

At the end of Round 2, I had lost another 3 pounds but I’m having a harder time keeping that weight off. All in all, I lost about 9 pounds total and have kept 6 off. 

Since then, I’ve continued intermittent fasting, eating my Fast Bars late morning, avoiding alcohol, and limiting dairy and carbs

I also tried out the Lumen so you can read how that changed my eating habits.

What can I say? This cynical New Yorker became a believer. 

Pros of the ProLon Diet

​There were many pros for me: 

  • I lost some stubborn belly fat and have kept it off
  • I’m in my 40s and it’s not so easy to lose weight anymore but the weight came off and stayed off
    • my stomach was flatter
    • I worried it was temporary water weight but I’ve kept the weight off
  • Ate only when hungry and not to the point of feeling full
  • Good energy
  • Drank less caffeine
  • No meal planning and very easy to follow
  • Learned a lot from the Prolon coach
  • I eat well but I made some positive changes post-Prolon
    • intermittent fasting
    • limit carbs and alcohol
    • keeping fruit to 2 servings and trying to stick to berries which have less sugar
    • eating leafy greens throughout the day
    • trying to eat my fruits and vegetables rather than blending them in a smoothie
    • drinking more tea
    • staying hydrated
    • learning it’s OK to skip a workout

Cons of the Prolon Diet

There are some cons to Prolon including:

  • You can’t have any real social plans during the 5 to 6 days of the program
    • Day 6 is the Transition Day and for 12 hours, you want to eat small, light meals.
  • I missed doing my daily workouts
  • Disliked cooking for my family during the week
  • Felt unfulfilled without fruits and vegetables
  • Felt conflicted in front of my tween daughter because I don’t like dieting or limiting my food intake in front of her
  • Disliked the red pepper soup and the NR-1 supplements
  • It felt strange rationing my crackers and olives for later considering how small the portions were
  • Worried about keeping the weight off after the round ended
ProLon Fasting Nutrition Program -The 5-Day Fast With Food – Prolon FMD

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After Completing ProLon

ProLon recommends continuing to intermittent fast and to live a healthy lifestyle. I find that using their Fast Bars or Fast Shakes help me to stay on track. You can read my full review of their Fast Bars here.

ProLon Fast Bars or Fasting Shakes

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Final Thoughts

Honestly, I loved the program. I was doubtful that I could keep the weight off but so far, I have had success. The ProLon diet forced me to make some changes in my diet going forward: less dairy, lower carbs, reduced snacking, and watching my fruit intake.


Can You Drink Coffee on ProLon?

​Although some try to avoid caffeine completely, I allowed myself a cup of black coffee every morning. ProLon is OK with this as long as you don’t add cream and sweeteners. However, you cannot have another cup for the rest of the day.

Some opted to drink decaf coffee all day long which could help to curb cravings. Some days, I couldn’t even finish my coffee and this is coming from someone who always drinks at least two cups.

You can have 140 mg of caffeinated coffee or unlimited decaf coffee or 2 cups of black or green tea per day.

Can You Drink Matcha Tea?

No, you may not drink matcha tea during the five-day fast.

Can You Add Seasoning to the ProLon soups?

I didn’t add anything. While dried herbs are generally OK, you cannot add fresh herbs, orange peel, curry powder, or psyllium to the soups for fiber.

Can You Add Lemon?

Lemon water is OK but you can’t use the entire lemon. You may add up to 2 slices of lemon to your water daily. 

Can You Skip the ProLon supplements?

The supplements are recommended and if you skip them, you are missing that nourishment.

Are there any Physical Side Effects?

You may have gastric distress if it’s a complete deviation from your normal diet. Except for gas pains one evening, my stomach was fine.

Some people experience lower back pain which quickly goes away. Others may have headaches or migraines.

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