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My Experience With Prolon: Lessons Learned From 3 Fasts

ProLon - the Easy, Evidence-Based Way to do a 5-Day Fast

Designed to take the headache out of fasting (not literally, you may still have a headache for the first day or two), ProLon was invented by Dr. Valter Longo, an esteemed longevity researcher who is the head of longevity at USC. Dr. Longo’s book is aptly titled The Longevity Diet. 

His work on intermittent fasting and fasting-mimicking diets (FMD) has focused largely on using fasting to enhance cancer treatment and mitigate the negative impact of chemotherapy, with considerable success. Now, however, many people are using ProLon to help lower cholesterol, triglycerides, and blood sugar, combat insulin resistance, promote weight loss, and enhance immune function.

I have used Prolon three times now because I trust Dr. Longo, full stop. With so many influencers out there competing for our “nutrition attention,” I find Dr. Longo to be one of the most credible, and that is why I am, and will continue to be, a Prolon customer. 

What is the Prolon “fasting mimicking diet?”

Before I get into my experience with ProLon, fasting, and calorie restriction, let’s quickly define some key terms:

  • Fasting – a complete absence of food intake. Prolonged fasting usually means at least 3 days in humans.
  • Intermittent fasting or alternate-day fasting – a long-term practice of fasting every other day, with standard food intake on non-fasting days.
  • Fasting mimetics – pharmacological agents that trigger some of the effects of fasting.
  • Fasting mimicking diet (FMD) – a dietary regimen composed of macronutrients and micronutrients, with minimal calorie restriction, designed to trigger a response akin to fasting. Specifically, to influence levels of glucose and IGF-1.
  • Caloric restriction – A 20-40 percent reduction in standard calorie intake, but a standard intake of micronutrients (i.e. vitamins and minerals, etc.).

ProLon is a fasting mimicking diet (FMD), which typically refers to a diet that contains no animal protein, low amounts of plant protein, very low amounts of saturated fat, high amounts of unsaturated fats, very low amounts of sugars, and high amounts of complex carbohydrates.

Why was ProLon invented?

Valter Longo designed ProLon to support people undergoing chemotherapy or radiotherapy for cancer. This is, in part, because intermittent fasting has been found to reduce levels of insulin-like growth factor-1 (IGF-1).

Lowering levels of IGF-1 can enhance the resistance of normal cells to chemotherapy-dependent damage while simultaneously increasing the susceptibility of a large number of tumors to chemo and radiotherapy. 1 2 3

ProLon may have been designed to support people during cancer treatment, but it is now being used and researched for its potential anti-aging benefits. That’s because Longo, and many others, are convinced that decreasing IGF-1 levels can have a significant effect on slowing down the aging process by promoting stem cell-based regeneration and immune system ‘rejuvenation’.

ProLon Pros vs. Cons


  • Backed by years of extensive research from a giant in the field of longevity
  • All of your food is contained in one box, which offers convenience & simplicity
  • Fasting triggers euphoria and high energy in many people
  • Enter autophagy, a state where the body kills off unhealthy cells, without losing muscle
  • Some food is allowed, which bypasses strict fasting


  • Five days of fasting feels like a long time
  • Hard to maintain with kids
  • Fasting increases uric acid
  • Lots of packaging and waste – ProLon definitely isn’t sustainable or eco-friendly

Which ProLon Fast Day is the Hardest?

ProLon is designed as a five day fast.

Everyone’s body is different. Based on my experience with ProLon, days 1 and 5 are the hardest, by far.

Although day 1 is one of the highest calorie days, it starts to dawn on you what you have signed up for. Your body isn’t yet in ketosis, and heading to bed without dinner feels abnormal, even a little depressing.

However, when I wake up on day 2, things settle, and some of the euphoria people report on ProLon starts to kick in.

The elevated mood, and energy boost associated with fasting is a real phenomenon that I have experienced first-hand each time I have tried ProLon.

Completing a ProLon fast is not easy. Lasting the full five days on a severely calorie restricted diet becomes harder the longer into the week you go. I find that by day 5 I am exhausted with the protocol, and vey tired of the powdered soups in particular.

Each time I have done ProLon, I am tempted to end the fast on the evening of day five, but instead head to bed again without dinner and wait for the morning of day 6 to break my fast by slowly introducing small portions of gentle on the stomach plant foods, like oats or sweet potato soup.

Which ProLon Meals Taste the Best?

I actually ordered some of the fasting bars to keep in the pantry after ProLon.

The L-Bars, and olives are also tasty.

The food that I have the toughest time with during the FMD, are the soups. Everyday of the fast has at least some soup, which is powdered. You can’t just drop a soup in and pur water over it, either. That will result in lumps.

After several lumpy soups haphazardly prepared, I started pouring the soup packet in a bowl and thoroughly whisking the mixture to make sure all of the powder had dissolved.

Letting the soups “steep” with a plate placed over the bowls will soften the dried peas which are added to the minestrone & quinoa soup mix.

My Areas of Concern During ProLon

Fasting, including fasting mimicking diets, increase uric acid levels.

One of the things I have learned building Gene Food, is that I have increased risk for elevated levels of uric acid based on my genetics. That risk is compounded by the fact that we live in a high altitude environment, which exacerbates the problem.

Unfortunately, I haven’t had time to get a before and after blood draw when doing ProLon, but I did have my blood drawn immediately after completing a ProLon kit, and did see elevated uric acid.

I try to mitigate some of the increase in uric acid levels during ProLon by taking quercetin, which is a supplement that can help make urin more alkaline, which in turn, helps the body get rid of more uric acid.

It is also crucial to drink plenty of water during a ProLon fast.

Not sure what to eat?

Gene Food uses a proprietary algorithm to divide people into one of twenty diet types based on genetics. We score for fat metabolism, histamine clearance, carbohydrate tolerance, and more. Where do you fit?

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Should you try ProLon?

After looking at the research, I’m convinced that ProLon has some major selling points. Aside from its likely benefits for anyone undergoing cancer treatment, there may well be some considerable benefits for healthier individuals as well as those with immune system problems.

ProLon makes it super simple to give fasting a try without having to worry about malnutrition. The product packaging is easy on the eye and the food, by most accounts, tastes pretty delicious! The cost is likely to be prohibitive for many people, however, although there are discounts available if you buy in bulk or sign up for a subscription.

One interesting additional benefit of ProLon is that it seems to make a person reassess their relationship to food (and alcohol!). After ‘fasting’ for five days, you’ll probably think harder about everything you put in your mouth. Smaller portion sizes may suddenly seem much more reasonable, and you’re likely to be better at forgoing snacks and foods that were unhealthy habits. That said, there are probably easier ways to promote mindfulness around food.

Interested in a mimicking fasting diet but don’t want to try ProLon? Your best bet is to work with a qualified nutritionist. That’s because trying to design your own is liable to lead to dangerously low blood pressure, blood glucose, palpitations, and other possibly fatal complications. This isn’t just marketing hype. Even on ProLon, which took decades to design, your assigned nutritional advisor will likely tell you to avoid driving or any strenuous or stressful activity because it could be more dangerous than usual.

In fact, the makers of ProLon have a long list on their website of folks who shouldn’t use the product. If none of these caveats apply to you, it seems well worth giving ProLon a go. If you do, be sure to swing by the comment section to let me know how you get on.

John O'Connor

John O'Connor is the founder of Gene Food, a nutrigenomic startup helping people all over the world personalize nutrition. John is the host of the Gene Food Podcast and a health coach trained at Duke's Integrative Medicine Program. Read his full bio here.

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  1. Janice Freebersyser says:

    Prolon Round 1 Day 4 and I have the ability to see the outline of bones in my feet and hands. Walk barefoot on my hardwood floors. Stretching with greater ease. My mind seems to be flying faster than in many years past. I have mild MS and also Moderate RA. I weened myself off all prescription medications to do this FMD and I am so thrilled with how I am doing. I invested in a 3 month kit program. I plan to incorporate a vegetarian based diet after this and use intermittent fasting with Prolon L Bars. Excited for a healthy future.


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