Prolon Review (2024 Upd.) Is This Fasting Diet Really Work?

Last Updated on February, 2024

Fasting with food. That’s what the ProLon 5-day fast mimicking diet plan promises us—consuming a limited amount of calories over 5 days while maintaining a fasting state instead of going zero calories and starving to reap the benefits of fasting. 

But is it really effective and worth the effort?

Keep reading to know more about the ProLon diet plan, what is included, how it works, my experience, and much more.

What is the Prolon Diet?

a screenshot of the prolon 5-day diet work program

The ProLon diet plan claims to use a fasting-mimicking technology that can keep the body in a fasting state while allowing foods to keep the body cells nourished without triggering nutrient sensors that can break the fast.

ProLon is a patented diet program introduced by the Longevity Institute of the University of Southern California. It was discovered and developed under the direction of Dr. Valter Longo, Ph.D.

This nourished fasting is enabled through a 100% plant-based technology. It is actually vegan, apart from the use of honey in certain products. The nourished fasting fine-tunes cells to support healthy aging and prevents the need for food-free or water-only fasts that can drain your energy levels. 

The ProLon product line offers two fasting nutrition kits, of which the 5-day fasting-mimicking diet (FMD) plan is the star.

On this 5-day diet, instead of completely starving the cells, a limited number of calories over five days will mimic a fasting state to reset the body’s metabolism and help improve response to insulin, resulting in optimal health and weight loss.

With over 20 years under research and development, the ProLon fast-mimicking eating plan is clinically proven for its ability to rejuvenate the body. (1)

The fast mimicking technology used in ProLon has 32 growing global clinical trials that test the effects and benefits of it on healthspan. (2)

What is Included in the Prolon Diet Kit?

This 5-day FMD kit has all the food items you should eat for the fasting period. The foods are segmented into five separate boxes, one for each day of the fast.

At first sight, the kit contains:

  • A water bottle
  • A variety of foods in five boxes: energy nut bar, dried soup blends, drinks, supplements, snacks, and teas
  • A meal program card
  • Instructions to follow the diet

The meal plan differs for each day and is designed to be taken in four portions: breakfast, lunch, snack, and dinner, conforming to a typical eating routine. 

However, if you have certain eating habits, partitioning each day’s food into three or any number of times as you see fit will work as long as you stick only to the foods given for the day.

So you can make the partitioning of the foods work to your flexibility or follow the meal program instructions card given by ProLon.

Although the foods are different each day, there are repeats of the same foods with a few variances.

a screenshot of the day 1 box of the 5 day prolon program

For example, you’ll find the specific foods listed below in the day 1 box:

  • Algal oil (2 sachets)
  • Tomato soup
  • Minestrone soup
  • NR-1 (2 sachets)
  • Tea
  • Spearmint tea
  • Kale crackers
  • Olives with sea salt
  • L- Bar nut-based X 2
  • L- Bar choco crisp

The other four days have similar foods except for the addition of the L-drink. During your purchase, you can switch the soup options as below;

Original ProLon Variety

  • Tomato soup
  • Minestrone
  • Mushroom
  • Vegetable 
  • Minestrone & quinoa 

Variety option 2

  • Butternut squash
  • Butternut squash with Quinoa
  • Black bean
  • Spinach with white bean

Variety option 3

  • Carrot ginger 
  • Green peas & chives
  • Red bell pepper & onion 
  • Lentil curry
  • Chickpea & leeks

Also, the tea options include hibiscus and lemon spearmint.

*L Drink– A vegetable-based energy drink to provide nutritional support during the fasting diet. The plant-derived glycerol in the drink protects the amino acids and promotes the hydration of the cells. (3)

Foods to Add/Avoid While on the Prolon Diet

pictures of the prolon 5 day program

ProLon says, “Additions are discouraged to minimize the risk of breaking the fast.” So, you should strictly stick to the meals provided in the diet kit and consume only the allowed foods for the day.

However, ProLon allows you to make a few select additions, as listed below.(4):

  • Unlimited herbal teas (sweetener and caffeine-free)
  • Any sweetener-free type of sparkling water
  • A cup of black coffee- Up to 140 mg of caffeine intake per day
  • Up to 1 tsp of dry herbs or spices per day can be added to soups or other foods of the diet plan
  • Up to 1 tsp of sea salt per day
  • Up to 2 slices of squeezed lemon per day 
  • Up to 2 sticks of sugar-free gum

The above additions don’t really make a significant difference. It only makes the diet plan more manageable while accommodating certain habits like caffeine. 

On top of that, ProLon also says certain food additions are allowed “only as a last resort if you are incredibly hungry that you feel like you are going to break the fast.”

In such cases, ProLon suggests the following options:

  • A slice or two of apple or
  • One stalk of celery or
  • One small baby cucumber of 5- 6 inches in length per day

How Does the 5-Day Prolon Diet Work?

It goes without saying since this is a fast-mimicking diet, maintaining fast at optimal levels requires the diet to be highly calorie-restrictive. 

a screenshot of the prolon 5 day program steps

You are looking at around 1150 calories on day 1 and around 800 calories per day from day 2- 5. It is a very low-calorie diet.

The science behind the ProLon 5-day fast is;

  • Day 1: Transforming to a fasting state

The body transitions to a fasting state and fat-burning mode and prepares for cellular cleanup. 

  • Day 2: Fat burning & ketogenesis

Fat burning increases and initiates ketogenesis to produce ketone. By the end of 48 hours, ketosis will begin. (5)

  • Day 3: Autophagy– Cellular cleanup state

Fat burning and ketone production/ utilization continue while autophagy begins.

  • Day 4: Cellular rejuvenation

Fat burning and cellular cleaning/ renewal continue. 

  • Day 5: Renewal & change

Fast is completed. Cellular renewal continues beyond day 5. 

To effectively lose weight, the Prolon 5-day fast should be followed monthly for at least three consecutive months.

Only then will your body be able to reset the metabolism and maintain the health benefits of the fast while losing weight? 

According to the ProLon website, three cycles of this 5-day fasting can reduce your bio-age by 2.5 years; therefore, it claims to be the Reverse Bioage Program.

As I already mentioned early on, ProLon also offers a one-day fast called ReSet by ProLon. This nutrition kit supports intermittent fasting.


But for reliable results on weight loss, trimming belly fat, and improving metabolic health, the 5-day nutrition kit is the way to go.

prolon 5 day program box

What to Do After the 5-Day ProLon Fasting Mimicking Diet?

ProLon also guides you on how to gradually transition and ease out of the 5-day fasting mode instead of deep diving back into your regular meals that can otherwise interrupt the balance in the transition.

Below are tips shared by ProLon on the meal instruction card of the diet plan:

  • Follow the fasting-mimicking diet as instructed by ProLon through to day 5.
  • From day 6 onwards, gradually switch to your regular, healthy diet. Begin with liquid foods like soups and fruit juice. And follow with light meals with rice, pasta, and any low-carb diet with small portions of protein.
  • Keep meals light and small during the first 12 hours of day 6.
  • On day 7, you can completely revert to your regular healthy diet.

Note: ProLon advises you to consult your healthcare professional to determine the best plan to help you transition from the diet.

My Experience on the Prolon Diet

Overall Take on the Diet

I was pretty excited to receive the 5 days fasting mimicking diet package from ProLon. The box had five small boxes for each day of the fast and a water bottle for L- drink. 

Each one of the boxes, although small, was packed with several food items for the day. From breakfast bars to afternoon snack and herbal tea options, everything you should eat during the day was included. 

An instruction card was included on how to follow the diet plan and consume the meals throughout the day. However, since I religiously follow an intermittent fasting diet, incorporating this fast-mimicking diet wasn’t too difficult. 

On intermittent fasting, my eating window is usually from 10 in the morning to 4 in the evening.

Most days, I try to constrict the eating window and stick to a single but full meal, and I am good for the day. So, I don’t necessarily eat through the whole window.

a screenshot of the prolon 5 day diet work program sample schedule

Trying to fit my lifestyle diet to accommodate the 5 days ProLon fast, I partitioned each day’s meal into two main portions and consumed one part in the morning around 10.00 a.m. and the other part during mid-day around 2.30- 3.00 p.m. I fit the tea and snacks in between the two portions as well. 

This partitioning worked because my metabolism is already used to nutrition within a given period. Still, the drop in calories felt a bit overwhelming, especially during days 2-5, but I’d say I managed fine; therefore, my day-by-day experience is pretty similar.

I strongly believe that mentally preparing yourself to take on a diet of this nature makes a big difference in the results of the diet.

How Were the Meals?

a screenshot of whats included in the 5 day program

I am usually not a picky eater. Also, since I do not have any food allergies or medical conditions restricting any foods, I am usually open to most food items. Obviously, there’s only so much you can expect from a highly calorie-restrictive diet. So, for me, most of the ProLon food items were “okay” and edible. 

Below, I have described how the ProLon food items tasted to me;

But when you primarily consume fats and restrict carbs:

  • Soups
  • Minestrone soup– This soup comes with pieces of vegetables, and it was my first favorite. It tasted reasonable and was filling. 
  • Mushroom soup– This soup wasn’t pleasing to the eye, but it tasted fine.
  • Minestrone with Quinoa– The Quinoa gave this soup more of a solid substance that made it filling, and the taste was good.
  • Vegetable soup– Appearance vise, the vegetable soup was on top and taste wise also it was to my palate.
  • Tomato soup– This was my least favorite because, usually, I’m not too fond of tangy foods. And tomato is at the top of the list. So this soup wasn’t for my taste buds, but it was edible.
  • Snacks
  • Kale crackers– These crackers were crunchy and felt good to snack on.
  • Olives with sea salt– This snack was a hit for me because it was salty.
  • Nut bars- You can take these as breakfast bars or an afternoon snack.
  • Choco crisp bar– This was like a chocolate bar, and I liked the taste of it.
  • L- -bar nut-based– This was chewy and filled with nuts, flax seeds, and coconut. It tasted good but had a limited sweet taste.
  • Supplements- 
  • Daily multivitamin– Capsule form
  • Omega 3– Capsule form 
  • L- drinkThis drink had a subtle flavor of orange (alternates between berry flavors, too) but otherwise no taste. You can also add a hibiscus tea bag to flavor the drink. 

Also, you are supposed to sip on it throughout the day, but I drank it within the window like drinking regular water.

I am not a tea drinker. So whenever I feel like sipping on something other than water, I have the herbal tea in the box. Otherwise, it was mainly water for me.

The above-listed soups belong to the ProLon “Original” option.

ProLon also offers another set of soup variety that includes:

  • Butternut squash soup- This tastes just like butternut squash and has a sour taste. The thick texture makes you feel full.
  • Butternut squash with Quinoa soup- This has a nice flavor, but the texture was comparatively thinner than the butternut-only soup.
  • Spinach with white bean soup- This soup was a bit bland and more on the spinach-tasting side. 
  • Black bean soup- Although black beans did not have a heavy taste of it. But it looked pleasing and tasted good.

Refeeding and Recovery Phase

Above, I have included the instructions that ProLon gives on refeeding after the fasting period.

It is absolutely crucial to carefully choose what to feed your body because you don’t want to burden your digestive system to work harder than necessary after a period of balanced functioning. 

You have to let it adapt to your normal diet slowly. That is best done by refeeding on simple and light foods like soups, bone broth, and fruits. 

Loading on carbohydrate meals will spike glucose and then insulin. This will, in turn, affect the mood and energy levels. 

In my case, of course, I turned to a solid carb and protein-based meal, plus a dessert on day 6.

It made me uneasy because the meal didn’t seem to digest for a long time. So that whole time was a bit uncomfortable. 

prolon 5 day diet work program banner

At the same time, it prevented me from eating anything else, too. So that was a positive! Other than that, I was okay overall. On day 7, I continued intermittent fasting, and my system seemed to have reverted to normal.

How Did I Feel After the Prolon FMD?

After the Prolon FMD, I wasn’t feeling super elated, nor was I feeling lethargic and energy drained. But I was hungry before my eating window, which I usually don’t feel.

The benefits of the Prolon fasting-mimicking diet are mostly internal. You can’t see the fat burning or the cellular clean up or renewal, at least not without measuring. And these measurements require lab testing to reveal results.

Was it Difficult?

As I already mentioned, the calorie restriction made it a bit overwhelming for me despite being used to eating one meal a day (OMAD). 

But it wasn’t too unbearable, and it pushed me to break the fast or turn to the additional recommendations from ProLon to keep the fast going. This may not be the case for all. The first time might be a bit difficult, but in the long run, it’ll be worth it.

Also, when compared to a water-only fast, the ProLon fast is definitely a LOT EASIER and COMFORTABLE.

Would I Do it Again?

Yes, I would absolutely do it again, especially since the recommended cycle is three times every month. I am excited for the results in the long run. Also, since it wasn’t as energy-draining for me, I can see myself fitting the ProLon fast into my routine.

prolon 5 day program image
Prolon 5 – Day Program

Is the Prolon Diet Right for You?

Fasting diets are not for all. Based on age and health status, the ability to fast changes.

Individuals who will benefit from doing the ProLon FMD include:

  • Pre diabetics
  • Diabetics- those with insulin resistance
  • Those with excess belly fat
  • Generally, healthy people looking to kickstart a health plan
  • Those who are overweight

The ProLon diet is not suitable for:

  • People with a history of eating disorder
  • Pregnant or breastfeeding mothers
  • Younger than 18 or older than 70
  • Those who are underweight, malnourished, or have experienced protein deficiency
  • Those who are hyperactive
  • Those who have allergies to the plant-based ingredients used in the diet kit
  • Those who have a cough, diarrhea, or fever
  • Those showing signs of active infection or at a risk for recurrent infections

Furthermore, ProLon also advises not to start a fasting diet without consulting a doctor if the following conditions apply to you:

  • Cancer
  • Diabetes type 1 and 2
  • Congestive heart failure
  • A history of fainting

Exercising a few safety tips while fasting on a calorie-restrictive diet will help elevate the experience without any side effects.

Some safety precautions include:

  • Avoiding activities like hot tub, sauna, prolonged sun exposure, long-distance driving, etc
  • Avoid any strenuous exercises or activities that require high energy production. Instead, you can walk, stretch, or do yoga.
  • Avoid scheduling a ProLon diet amidst menstruation, as it can affect your hormone levels.
  • Pay attention to how you feel: headache, dizziness, and difficulty concentrating. Ensure you don’t push yourself when feeling fatigued.

ProLon Vs. DIY FMD

a screenshot of a person using prolon 5 day program

Creating a DIY fasting kit is absolutely possible. But it comes with its own restrictions:

  • You have to be extremely comprehensive when creating a DIY FMD. 
  • You have to strictly and diligently factor in several variables like calories, macronutrients, and micronutrients.
  • You have to wisely choose the food options and study in great detail as to how each one of these foods and other components in the food can affect your fasting state. 
  • You have to pay close attention to IGF-1 hormone, mTOR protein and many similar variables that can compromise your fasting state when you cross a fine line due to a miscalculation in calorie count or failure to consider minor compounds in a food option.
  • And more.

Hence the ProLon diet serves as the safest bet to get you into and sustain you in a fasting state.

Choosing ProLon gives you the following advantages:

  • Research-backed plant-based food formulations that have been extensively studied in labs and humans.
  • Saves time.
  • Zero planning effort.

Benefits of the Prolon Fasting Mimicking Diet

a screenshot of the benefits of the prolon 5 day program

Fasting diets like ProLon FMD offer many cosmetic and long-term health benefits. But it is worth noting that not everyone will benefit the same way and at the same rate.

The possible benefits are listed below:

  • Fat-focused weight loss– The fast can kick start fat-targeted body weight loss, especially belly fat while protecting lean body mass. On average, the ProLon fast, when continued for three cycles, can help lose a few pounds (users have reported 5-6 pounds).
  • Can support metabolic and heart health– According to research, an FMD can help maintain a healthy systolic blood pressure by lowering blood pressure, LDL, triglycerides, and total cholesterol that significantly contribute as risk factors of heart disease, thereby supporting overall enhanced metabolic activity.
  • Potential to improve aging through cellular rejuvenation (autophagy)– The ProLon diet can support healthy aging by promoting cellular renewal through autophagy. So older cells are replaced with new and healthier cells, contributing to rejuvenation inside out, healthy aging, and longevity.
  • Healthier, younger-looking skin– After three cycles of the ProLon FMD, it was clinically shown that rejuvenation can contribute to cosmetic benefits by reducing fine lines and wrinkles. 
  • Improves sense of well-being and mood– The rejuvenation supports enhanced mental clarity, performance, and vibrance, making you feel empowered and full of energy.
  • Improves relationship with food– The proLon diet may help you understand, appreciate, and change your relationship with your food to avoid mindless and extra-calorie consumption. It will also help you determine your gluten and lactose food sensitivities.
  • Portion control– The improved food relationship will help the brain reset and get used to portion sizes you should be eating instead of what you are used to eating.
  • Conveniently fits into any lifestyle– The ProLon fast requires no complicated preparation process. So it allows you to incorporate it into your routine with minimal hassle.
  • Does not require long-term commitment– The proLon fast only needs 5 days of strict fasting to bring about the many benefits listed above. The short commitment period makes it easier to accomplish.
  • No need for meal planning– Since the nutrition kit provides you with all the foods you must eat, it takes away the stress of making calorie-restricted meal decisions.

Drawbacks of the Prolon Fasting Mimicking Diet

Although there are significant benefits to the ProLon FMD, it also comes with certain downsides, as listed below:

  • The cost can be a concern for some– Since the ProLon 5-day fast box runs at $190 each, first-time purchases or those looking for multiple box purchases can be expensive. But ProLon does offer discounts.
  • Limits your food options and is not customizable– The foods in the box are pre-packaged with standard options, so it doesn’t allow customizability to accommodate preferences or even for medical reasons. 

This also limits the food options you can eat within those 5 days, and some may grow weary if they are used to eating fresh produce.

  • Limited body changes due to short-term diet– The short-term diet only enables a short-term ketosis process. This results in limited body composition changes.
  • It is not suitable for all- The ProLon fast is highly calorie-restrictive, and low-calorie intake is not suitable for everyone. Those who are used to being active may have side effects like hunger issues and compromised exercising ability, especially during the first few days.

ProLon also highlights that some possible medical side effects include low blood sugar, constipation, fainting, irritability, fatigue, weakness, and headaches.

  • Visibility of results takes time– Since the body changes mostly take place under the skin, the visibility of the results will take time, affecting the trust you place in the process. You must research and read more on fasting and its benefits to keep you motivated.
  • Some may consider the packaging unsustainable- The 5 days of the food supply is packaged into several small plastic wrappers and the drink plastic bottle8+9*. 

So, each day, there is quite an amount of disposable waste. If ProLon can turn to recyclable options like disposable packaging, it would be more environmentally friendly. 

How Much Does the Prolon Fasting Mimicking Diet Cost?

a screenshot of the prolon 5 day program price

A one-time purchase of the ProLon 5-day fasting-mimicking diet retails at $190. If you opt for a subscription you can save $20 per diet kit. You can easily renew or stop your subscription at any time. 

The one-day ReSet fasting kit retails at $39. If you are on the fence about ProLon, you can start with this diet kit, although the 5-day fasting-mimicking diet kit is the real diet. 

Other Reviews you might want to read:

Frequently Asked Questions

Yes, one can consume coffee during the ProLon 5-day FMD. The recommended amount is one cup of black coffee per day, which contains approximately 140 mg of caffeine.

Yes, you can season your soup with up to 1 tsp each of salt, spices, and herbs every day during the 5-day fast.

An FMD is different from intermittent fasting because it allows for reduced calorie intake rather than complete avoidance of food. On the other hand, intermittent fasting completely restricts food intake regardless of the amount of calories consumed during a specific period of time.

ProLon Review: Last Thoughts

Although fasting is not for everyone, it can bring immense health benefits to the human body by giving it a rest from having to work to process the calories we consume every day.

The ProLon diet is an excellent way to explore the benefits of fasting without having to really fast and starve yourself. 

From weight loss to elevated mood to healthier skin and everything in between that is invisible to the naked eye, ProLon can really get you started on the right path for a healthier and longer life.

You can also try the ProLon diet to experience the difference!

Prolon 5-Day Program
prolon 5 day program image
Taste Wise




Overall Score


Fat-focused weight loss
Can support metabolic and heart health
Potential to improve aging through cellular rejuvenation (autophagy)
Healthier, younger-looking skin
Does not require long-term commitment
Improves relationship with food
Get the BEST PRICE valid until the end of February
The cost can be a concern for some
Some may consider the packaging unsustainable