If you’ve been exploring ways to reset your body, lose stubborn weight, and tap into the science of longevity, chances are you’ve come across ProLon. Developed by Dr. Valter Longo at the University of Southern California’s Longevity Institute, ProLon is a fasting mimicking diet (FMD) that lets you eat real food while your body thinks it’s fasting. It sounds almost too good to be true — but behind this program lies over 25 years of research, 47 clinical trials, and more than 200 patents.
In our testing, we found that ProLon offers a refreshingly different approach to health and wellness. Rather than asking you to give up food entirely, it provides a carefully calibrated 5-day meal kit that delivers just enough nutrients to keep your body functioning while triggering the same cellular benefits as a water-only fast. The result? Autophagy, fat burning, reduced inflammation, and even a measurable reduction in biological age — all without starving yourself.
Whether you’re looking to shed a few pounds, support healthy aging, or simply give your body a deep cellular cleanse, ProLon has a growing lineup of products designed to fit different lifestyles and goals. In this guide, we’ll break down each product, compare their features, and help you decide which one is right for you. Check out the full ProLon lineup here →
Why ProLon? The Science Behind the Brand
What sets ProLon apart from virtually every other diet program on the market is the depth of science behind it. Dr. Valter Longo, one of the world’s leading longevity researchers, spent decades studying how fasting affects the human body at a cellular level. His research, conducted at USC and in collaboration with 18 prestigious universities worldwide, led to the discovery that you don’t need to stop eating entirely to trigger fasting’s most powerful benefits.
The key is autophagy — the process by which your cells break down and recycle damaged components, essentially performing a deep internal clean-up. This process was so significant that it earned the 2016 Nobel Prize in Medicine. ProLon’s proprietary meal formulations are designed to avoid activating your body’s nutrient-sensing pathways (IGF-1, mTOR, and AMPK), which means your cells enter a fasting state even though you’re still eating.
The clinical results speak for themselves. In a landmark 2024 study published in Nature, three cycles of the ProLon Fasting Mimicking Diet were shown to lower participants’ biological age by an average of 2.5 years compared to their actual age. Other clinical trials have demonstrated an average weight loss of 5.7 pounds and a 1.6-inch reduction in waist circumference after just three monthly cycles. The program has been trusted by over 12,200 medical professionals and has served more than 1 million customers worldwide.
ProLon 5-Day Fasting Mimicking Diet — The Flagship Program
The ProLon 5-Day FMD is the cornerstone of the entire ProLon ecosystem. It’s a 5-day, pre-packaged, plant-based meal program that arrives at your door in five clearly labeled boxes — one for each day. Each box contains everything you need: soups, nut bars, kale crackers, olives, herbal teas, supplements (including algal oil and a proprietary multivitamin), and the L-Drink glycerol-based energy solution.
Here’s how the calorie breakdown works:
| Day | Calories | What’s Happening in Your Body |
|---|---|---|
| Day 1 | ~1,100 | Transition into fasting; body shifts to fat-burning mode |
| Day 2 | 700–800 | Fat burning ramps up; ketogenesis begins |
| Day 3 | 700–800 | Deep autophagy; cellular clean-up intensifies |
| Day 4 | 700–800 | Cellular renewal and fat burning continue |
| Day 5 | 700–800 | Fasting completed; cellular renewal continues post-program |
The soups are the heart of each day’s meals. Depending on the variety you choose, you might find flavors like Minestrone, Tomato, Mushroom, Lentil Curry, Green Pea and Chives, Carrot Ginger, Chickpea and Leeks, or Butternut Squash. We found the soups to have a creamy consistency that’s surprisingly satisfying — not chalky like many powdered meal replacements. The nut bars (made with almonds, macadamias, and pecans) are genuinely tasty, and the kale crackers with Spanish olives provide a satisfying crunch on days when you need it most.
Each day follows a structured eating schedule: a nut-based bar for breakfast, a soup for lunch, an afternoon snack (kale crackers or olives on most days), and a second soup for dinner. Days 1 and 2 include a small Choco Crisp L-Bar as an evening treat, which we found was a genuine morale booster. The glycerol-based L-Drink, mixed with water in the included reusable ProLon bottle, provides an alternative energy source during days 2–5, helping protect lean muscle mass as your body shifts into fat-burning mode.
One thing that surprised us was the daily supplements — each box includes algal oil (a plant-based omega-3) and a proprietary NR-1 multivitamin and mineral packet. These aren’t afterthoughts; they’re integral to the formula, ensuring your body gets essential micronutrients even at drastically reduced calorie levels. The herbal teas (spearmint, lemon spearmint, and hibiscus) are caffeine-free and surprisingly comforting, especially during the lower-calorie days when you want something warm and flavorful.
During the 5 days, you’re allowed a few extras: up to one cup of black coffee per day (140mg caffeine max), unlimited sparkling water without sweeteners, a slice of lemon, and dried herbs or spices for the soups. ProLon also provides an emergency list — a small slice of apple, a celery stalk, or a Persian cucumber — for moments when hunger becomes truly overwhelming. In our experience, we didn’t need to use these, but knowing they’re there provides psychological comfort.
ProLon recommends completing the 5-day program once a month for three consecutive months for optimal results, then maintaining with one cycle every 1–6 months. After the 5 days, you follow a transition day with light, plant-based meals to ease your body back to normal eating. The kit includes a transition meal guide and even a suggested shopping list for your post-fast meals, which is a thoughtful touch.
Pricing: Starts at $175 for the Original variety, with options up to $215 for the Expanded variety. Subscription pricing is available and includes a free welcome kit with a water bottle, extra fasting bars, and shakes. HSA/FSA eligible.
Our take: The 5-Day FMD is the most impactful entry point into the ProLon system. It’s the program with the most clinical data behind it, and it delivers the full spectrum of fasting benefits — autophagy, fat loss, metabolic reset, and biological age reduction — in a manageable 5-day window.
See the latest pricing for the 5-Day FMD →
ProLon 5-Day FMD Next Gen — Certified Organic Upgrade
The ProLon Next Gen is the newest evolution of the 5-Day FMD, and it brings a significant upgrade: certified organic, ready-to-eat soups. Unlike the original program where soups come in powdered form and require hot water, the Next Gen features pre-made soups that you simply heat and enjoy. This makes the experience more convenient and, honestly, more appetizing.
The Next Gen maintains the same calorie structure and fasting-mimicking formula as the original, so you’re getting identical clinical benefits — just with a more premium, organic food experience. It’s rated 4.4 out of 5 stars based on over 1,836 customer reviews, which speaks to high satisfaction among users.
If you’re someone who values organic ingredients, prefers the convenience of ready-to-eat meals, or simply wants the most refined version of the ProLon experience, the Next Gen is worth the upgrade. The flavor profiles are also updated, with richer, more complex soup varieties that make the 5 days feel less like a “diet” and more like a curated culinary experience.
Pricing: $160 for the 5-day kit (competitive with the original when considering the organic upgrade).
ProLon 1-Day Reset Kit — Quick Reboot Between Cycles
Not ready to commit to 5 full days? Or looking for a way to maintain your fasting benefits between monthly cycles? The ProLon 1-Day Reset Kit is the answer. It’s a single-day fasting mimicking kit that you can use up to twice per week (but not during the 5-day program).
The Reset Kit includes a full day’s worth of ProLon’s scientifically formulated food: a Fast Bar for breakfast, tomato soup for lunch, olives and kale crackers for a snack, butternut squash soup for dinner, plus herbal teas and supplements. It follows the same principles as the 5-day program — low enough in calories and specific nutrients to keep your body in a fasting state — just condensed into a single day.
We found this product particularly appealing for people who want to “dip their toe in” before committing to the full 5-day program, or for those who’ve already completed their initial three cycles and want a lighter maintenance option. It’s rated an impressive 4.9 out of 5 stars from 89 reviews, making it one of the highest-rated products in the ProLon lineup.
Key benefits:
- Gentle introduction to fasting mimicking
- Maintains autophagy and metabolic benefits between full cycles
- Can be used on busy days when a 5-day commitment isn’t practical
- Helps recalibrate appetite and food cravings
ProLon 5:2 Program — The Intermittent Fasting Bridge
The ProLon 5:2 Program bridges the gap between the intensive 5-day FMD and everyday intermittent fasting. It includes four 1-Day Reset Kits that you spread across a month — typically two non-consecutive days per week for two weeks, or one day per week for four weeks. This approach mimics the popular 5:2 intermittent fasting pattern, but with ProLon’s scientifically formulated meals instead of generic calorie counting.
At $135 for four kits, the 5:2 Program offers excellent value compared to purchasing individual Reset Kits. It’s designed for people who want ongoing metabolic support and cellular maintenance without the intensity of a full 5-day fast. Think of it as a “slow and steady” approach to the same fasting benefits.
We recommend this program for:
- Gradual weight management between full FMD cycles
- Maintaining autophagy benefits over the long term
- People who find the 5-day program too demanding but still want measurable results
- Transitioning from the initial 3-month protocol to a sustainable long-term maintenance routine
Rated 4.4 out of 5 stars with over 1,836 reviews, the 5:2 Program has built a loyal following among users who appreciate its flexibility and consistency.
ProLon Fasting Bars — Daily Fasting Support Snack
ProLon Fasting Bars are the brand’s answer to a common problem: what do you eat during your fasting window when you’re doing daily intermittent fasting? These bars are specifically formulated to provide nourishment without breaking your fast. They’re made with a precise blend of macadamia nuts, almonds, pecans, and honey — ingredients that are carefully calibrated to avoid triggering nutrient-sensing pathways.
Each bar is designed to keep you satiated during fasting windows, making intermittent fasting significantly more manageable. They’re also useful as a pre-fast preparation snack or as part of the transition day after completing a 5-day FMD cycle.
We found them to be genuinely delicious — the nut-forward flavor with a touch of sweetness from honey makes them feel like a treat rather than a “diet food.” They’re individually wrapped and portable, making them easy to keep in your bag, desk, or car for whenever hunger strikes during a fasting window.
Key features:
- Scientifically formulated to support intermittent fasting without breaking the fast
- Made with premium nuts and honey
- Convenient, on-the-go format
- Complements all ProLon programs
ProLon Longevity Protein — Daily Muscle and Cellular Support
The ProLon Longevity Protein (L-Protein) is a daily supplement designed to support muscle maintenance and cellular health as part of ProLon’s broader longevity ecosystem. While the fasting programs handle the “reset” side of the equation, L-Protein supports the “rebuild” phase — providing your body with high-quality plant-based protein to maintain lean muscle mass and support cellular repair.
This is particularly important because one of the concerns with any calorie-restricted program is the potential loss of muscle mass. ProLon’s research showed that their FMD preserves lean muscle while reducing fat, and L-Protein helps maintain that balance during your regular eating days.
The protein is plant-based, consistent with ProLon’s overall nutritional philosophy, and blends easily into smoothies, shakes, or even soups. It’s an excellent complement to any of the fasting programs, ensuring that the weight you lose is fat — not muscle.
Learn more about Longevity Protein →
ProLon L-Pill — Daily Longevity Supplement
The ProLon L-Pill rounds out the ProLon daily wellness lineup as a targeted longevity supplement. While the fasting programs trigger deep cellular renewal on a periodic basis, the L-Pill is designed for daily use, supporting your body’s ongoing repair and maintenance mechanisms between fasting cycles.
Formulated based on Dr. Longo’s research into the specific nutrients and compounds that support healthy aging, the L-Pill complements the broader ProLon ecosystem. Think of it this way: the 5-Day FMD is your quarterly deep clean, the Fasting Bars and 1-Day Reset Kits are your weekly maintenance, and the L-Pill is your daily foundation.
We recommend the L-Pill for anyone who has completed at least one ProLon fasting cycle and wants to support their longevity goals on non-fasting days. It’s particularly well-suited for those following the Longevity Diet lifestyle that Dr. Longo outlines in his book — a mostly plant-based, pescatarian approach that emphasizes periods of caloric restriction combined with targeted supplementation.
What to Expect: A Realistic Day-by-Day Experience
One of the most common questions we get is what the 5-day ProLon experience actually feels like. Based on our testing and extensive user feedback, here’s a realistic overview:
Day 1 feels surprisingly manageable. At approximately 1,100 calories, you’re eating enough to feel satisfied. The transition into fat-burning mode begins, but you won’t feel dramatically different. This is the day to enjoy the higher food volume and prepare mentally for the days ahead.
Day 2 is when reality sets in. With calories dropping to 700–800, you’ll likely feel hungry, especially if you’re used to eating larger meals. Fat burning ramps up significantly and ketogenesis begins — your body starts producing ketones as an alternative fuel source. We recommend drinking plenty of water and the L-Drink throughout the day. If you’re a regular coffee drinker, the reduced caffeine may trigger a mild headache — this is normal and usually passes by Day 3.
Day 3 is often described as the turning point. Hunger actually begins to subside for many people as ketone production increases and your body fully adapts to burning fat for fuel. This is also when autophagy deepens — your cells are actively breaking down and recycling damaged components. Some users report a surprising sense of mental clarity on this day, despite the low calorie intake. Energy levels vary: some people feel great, others feel a bit sluggish.
Day 4 continues the cellular renewal process. By now, most people have adapted to the eating rhythm and portion sizes. The kale crackers and olives become highlights of the day. Sleep quality may fluctuate — some users report excellent sleep, others find it harder to settle. Fat burning and ketone production continue at their peak.
Day 5 is the home stretch. Hunger is typically at its lowest point, and there’s a psychological boost knowing the finish line is near. The program includes slightly less food on this day (no Choco Crisp treat), which can feel anticlimactic, but by now your body has completed the fasting cycle. Many users report feeling lighter, less bloated, and surprisingly energized.
Day 6 (Transition) is critically important and often overlooked. You’ll slowly reintroduce solid foods with light, plant-based meals — think vegetable soups, small portions of rice or pasta, and fresh fruits. Rushing back to heavy meals can undo much of the metabolic reset your body just completed. We found that following the transition guide carefully made a noticeable difference in how well we maintained our results.
ProLon and Your Health: Who Should (and Shouldn’t) Use It
While ProLon is backed by impressive science, it’s not for everyone. Understanding the contraindications is important before making a purchase.
ProLon is a good fit if you:
- Are generally healthy and between 18 and 70 years old
- Want to lose stubborn belly fat while preserving muscle mass
- Are interested in the longevity and cellular health benefits of fasting but can’t (or don’t want to) do a water-only fast
- Have been cleared by your doctor, especially if you have any pre-existing conditions
- Can commit to 5 days of restricted eating without intense physical activity
Avoid ProLon if you:
- Are pregnant, breastfeeding, or trying to conceive
- Have a history of eating disorders or disordered eating patterns
- Have active cancer, congestive heart failure, or a weakened immune system
- Are under 18 or over 70
- Currently have a fever, cough, diarrhea, or signs of active infection
- Have a history of fainting or significant blood pressure issues
If you have diabetes (type 1 or type 2), are on prescription medications, or have any chronic health condition, consult your healthcare provider before starting ProLon. The program can interact with certain medications and may require medical supervision, particularly for blood sugar management during the low-calorie days.
Product Comparison Table
| Product | Duration | Price | Best For | Rating |
|---|---|---|---|---|
| 5-Day FMD | 5 days | $175–$215 | Full cellular reset and fat loss | 4.4/5 (1,836+ reviews) |
| Next Gen | 5 days | $160 | Organic, ready-to-eat experience | 4.4/5 (1,836+ reviews) |
| 1-Day Reset | 1 day | ~$45 | Quick reboot, fasting intro | 4.9/5 (89 reviews) |
| 5:2 Program | 4 days/month | $135 | Ongoing maintenance, IF support | 4.4/5 (1,836+ reviews) |
| Fasting Bars | Ongoing | Varies | Daily IF window support | — |
| L-Protein | Ongoing | Varies | Muscle maintenance and longevity | — |
| L-Pill | Ongoing | Varies | Daily longevity supplementation | — |
How to Choose the Right ProLon Program for You
Choosing the right ProLon product depends on your experience level, goals, and lifestyle:
If you’re new to fasting: Start with the 1-Day Reset Kit. It’s a low-commitment way to experience how fasting mimicking feels without jumping into a 5-day program. Use it once or twice to see how your body responds.
If you want maximum results: Go straight for the 5-Day FMD (Original or Next Gen). Commit to three consecutive monthly cycles for the full clinical benefit — the biological age reduction, deep autophagy, and significant fat loss documented in the studies all come from this protocol.
If you prefer organic, ready-to-eat meals: The Next Gen is your best bet. Same fasting benefits, but with certified organic, pre-made soups that elevate the entire experience.
If you’ve completed the initial protocol and want maintenance: The 5:2 Program offers a sustainable long-term approach with four monthly Reset Kits. Supplement with Fasting Bars for daily intermittent fasting support and L-Protein for muscle maintenance.
If you’re budget-conscious: Start with the 1-Day Reset to test the waters, then invest in the 5-Day FMD when you’re ready to commit. ProLon frequently offers subscription discounts and promotions that bring the cost down significantly.
Frequently Asked Questions
How much weight can I expect to lose on ProLon?
In clinical trials, participants lost an average of 5.7 pounds and 1.6 inches from their waist after three monthly cycles of the 5-Day FMD. Individual results vary, and some of the initial weight loss may include water weight. Most users report that maintaining a healthy lifestyle between cycles helps sustain the results long term.
Can I drink coffee during the program?
ProLon recommends limiting caffeine, but you can have up to 140mg per day — roughly one 8–12 oz cup of black coffee, two cups of black or green tea, or six cups of decaf. No cream, sugar, or sweeteners allowed.
Is ProLon safe?
ProLon has been studied in 47 clinical trials and is trusted by over 12,200 medical professionals. However, it’s not suitable for everyone. You should avoid ProLon if you are pregnant or breastfeeding, under 18 or over 70, have a history of eating disorders, or have certain medical conditions (cancer, congestive heart failure, active infections). If you have diabetes, consult your healthcare provider before starting.
How is ProLon different from regular fasting?
Unlike water-only fasting, ProLon provides carefully formulated plant-based meals that keep you nourished while still triggering the same cellular fasting responses. This means you get the benefits of fasting — autophagy, fat burning, metabolic reset — without the extreme hunger, fatigue, and potential risks associated with complete food abstinence.
Is ProLon HSA/FSA eligible?
Yes, ProLon products are eligible for purchase and reimbursement through Flexible Spending Accounts (FSA) and Health Savings Accounts (HSA), which can significantly reduce the effective cost.
What does the food taste like?
In our experience, the soups are surprisingly good — creamy, well-seasoned, and filling. The nut bars are genuinely enjoyable (especially the Choco Crisp L-Bar dessert), and the kale crackers with olives provide a satisfying savory crunch. Taste is subjective, of course, but most reviewers agree that ProLon’s food quality exceeds expectations for a pre-packaged diet program.
Final Verdict: Is ProLon Worth It?
After reviewing the science, the products, and the real-world results, our answer is a qualified yes. ProLon stands apart from the crowded wellness market because it’s built on decades of rigorous scientific research, not marketing hype. The fasting mimicking technology is patented, clinically validated, and trusted by thousands of medical professionals. The fact that a 2024 study in Nature showed a 2.5-year reduction in biological age after just three cycles is remarkable by any standard.
The main drawback is cost — $175–$215 for a 5-day kit is a significant investment. But when you consider that it covers all your food for five days, comes with coaching support, and delivers clinically documented health benefits that go far beyond simple weight loss, the value proposition becomes clearer.
If you’re serious about cellular health, longevity, and metabolic optimization, ProLon is one of the few programs on the market with the science to back up its claims. Start with whatever product fits your comfort level and budget — and see for yourself why over a million customers worldwide have made ProLon part of their health routine.
