Paid editorial by Prolon
Metabolic health
Doctor explains
What your doctor never told you about visceral fat, and what actually gets rid of it
When you hear “visceral fat,” you probably picture the soft layer you can pinch in the mirror. That’s not it. Visceral fat is something else entirely, and it does far more than make your jeans hard to zip.
Dr. Joel Kahn, MD, FACC
Board-certified cardiologist and clinical professor of medicine
4.8 from 10,000+ reviews
Built on 25 years of clinical research
Developed, validated and published with leading research institutions and journals.
25 yrs
of development at the USC Longevity Institute
47+
peer-reviewed clinical studies
USC Longevity Institute
Where Prolon was developed, 25 years of research
Stanford
Research institution
Mayo Clinic
Research institution
Cedars-Sinai
Autophagy trial, Dec 2025
Nature Communications
Biological age study, 2024
Prolon was developed over 25 years at the USC Longevity Institute and validated across more than 47 peer-reviewed clinical studies. Institution and journal names denote published research and research collaboration, not endorsement.
The reframe
There are two types of fat in your body
The belly fat just below your skin is called subcutaneous fat. Annoying, but biologically relatively harmless.
Visceral fat sits deep inside the abdominal cavity, wrapped around your liver, intestines and heart. You cannot see it. You cannot pinch it. The scale will not show it to you.
Subcutaneous
The layer just below your skin. Visible, pinchable, and biologically relatively harmless.
Visceral
Deep inside the abdominal cavity, wrapped around your liver, intestines and heart.
Researchers have a name for this: TOFI, thin outside, fat inside
Plenty of adults look "not that overweight" on the outside yet carry high levels of visceral fat on the inside.
Scientists classify visceral fat as metabolically active tissue. It does not just store energy. It secretes. It disrupts. Every single day it interferes with the signalling of insulin, cortisol, estrogen and testosterone.
The measured risk
Why this hidden fat is more dangerous than the fat you can see
Visceral fat acts almost like a rogue organ running its own agenda inside your body. It is independently linked to heart disease, hypertension and stroke.
Risk #1 · Cardiovascular disease
A meta-analysis of 17 cohort studies involving 824,268 participants found that a high Visceral Adiposity Index (VAI) was associated with:1
55%
Higher risk of cardiovascular disease
RR = 1.55
45%
Higher risk of stroke
RR = 1.45
38%
Higher risk of cardiovascular death
RR = 1.38
23%
Higher risk of coronary heart disease
RR = 1.23
Risk #2 · Type 2 diabetes and insulin resistance
Visceral fat is now considered a primary driver of insulin resistance, the foundational dysfunction behind metabolic syndrome and Type 2 diabetes.2
Risk #3 · Chronic inflammation
It continuously releases inflammatory markers linked to accelerated cellular aging, cognitive decline and elevated disease risk across the board.3
Risk #4 · Hormonal disruption
In women, visceral fat accelerates around menopause as estrogen drops. In men, it drives down testosterone and accelerates muscle loss.4
This is not just extra fat. It is its own risk profile.
References
- 1. sciencedirect.com/science/article/pii/S0939475325003709
- 2. diabetesjournals.org/diabetes/article/51/10/2951
- 3. pmc.ncbi.nlm.nih.gov/articles/PMC9795790
- 4. pmc.ncbi.nlm.nih.gov/articles/PMC3964739
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
The part nobody flags
"I feel fine. How do I even know I have it?"
That is the most unsettling thing about visceral fat. It gives you almost no warning signs.
By the time you feel it, it has often been building for years.
What it does not give you
- No pain.
- No obvious symptoms.
- Nothing that makes you think something is wrong, until a blood panel comes back abnormal or a doctor mentions your blood pressure has been creeping up.
The absence of symptoms is not the same as the absence of risk.
Why now
Why visceral fat gets worse after 35
Between the ages of 30 and 70, visceral fat increases even when eating and exercise habits stay exactly the same.5
200%
Increase in men, ages 30 to 70
400%
Increase in women, ages 30 to 70
One main reason, besides the hormonal shift, is cortisol
High levels of stress hormones keep cortisol elevated, and cortisol specifically signals the body to store fat in the abdominal region.
This is the biological mechanism behind the stress belly that so many adults in their 40s and 50s carry. Your biology shifted. Your discipline did not.
What people call it
"Menopause belly"
For women, this is what the sudden change actually is.
"Dad bod" or "beer belly"
For men, the same tissue under a friendlier name.
Now that it is clear what visceral fat is and what it does, the obvious question is what actually removes it.
Reference
The obvious answers
"So what do I do about this visceral fat?"
When people want to lose visceral fat, or what they just refer to as belly fat, they reach for the obvious answers.
Cutting calories and eating clean
Makes sense in theory. But clinical trials show standard caloric restriction reduces visceral fat by only about 14%. The belly is consistently the last thing to respond, and cravings get harder to manage with age, not easier.6
14%
Visceral fat reduction from standard caloric restriction
Cardio and exercise
Also makes sense. But visceral fat follows a "first in, last out" pattern. You simply cannot exercise it away directly. People train for years and still carry the same hidden fat depot underneath.
First in, last out
The pattern visceral fat follows
GLP-1 medications
Yes, GLP-1s help you lose weight. But up to 40% of that loss could be muscle.7
They are popular for a reason, and they do work for total weight loss. But not all weight loss is equal. A good chunk of the weight lost on a GLP-1 is coming from your lean muscle and water, not just fat.
Muscle is one of the biggest drivers of how fast your metabolism runs. If you lose it, your body burns fewer calories at rest, and the weight comes back faster. You end up smaller, but not actually healthier.
That is one of the problems Prolon was scientifically designed to solve: lose visceral fat while protecting muscle.
Weight lost on a GLP-1
Up to 40%
Could be muscle
Reported across published GLP-1 trial analyses.7
References
- 6. onlinelibrary.wiley.com/doi/full/10.1002/oby.23660
- 7. pubmed.ncbi.nlm.nih.gov/38629387 and pubmed.ncbi.nlm.nih.gov/40289060
Prolon is a nutrition program, not a medication. Consult your healthcare provider before starting any new nutrition program, especially if you have a medical condition or are taking prescription medications.
What actually works
Introducing Prolon's 5-Day Fasting Mimicking Diet (FMD)
It is a patented, science-backed nutrition program developed over 25 years at the USC Longevity Institute, and validated across more than 47 peer-reviewed clinical studies, including Stanford and Mayo Clinic.
But what is it? A five-day done-for-you nutrition plan where every item is formulated to keep your body in a fasting state, while you eat.
It gives you not just weight loss, but the right weight loss. It is clinically proven to target visceral fat while protecting precious lean muscle.
25
Years of development at the USC Longevity Institute
47
Peer-reviewed clinical studies
Rated 4.8 based on 10,000+ reviews
Prolon 5-Day
Plant-based soups, bars, snacks, herbal teas and supplements, all pre-portioned and labeled for each specific day. No meal planning. No measuring. No guesswork.
In their own words
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1 million people have tried it
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Healthy, Good and Supportive Experience! Products in the 5 Day Fasting Mimicking Diet are high-quality and tasty. The program comes with professional and community support, too. I highly recommend the products and program!
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My husband and I love the results after the fast. We have more clarity, energy, and all over a healthier feel. Fortunately, we've always exercised and eaten a healthy diet, and gave up all alcohol; this fast was a great addition to all that. Hopefully, our blood work will reflect great changes. Thank you PROLON! Will be back next month.
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This was my third time using PROLON's 5 day fasting-mimicking diet. I am so thankful to have this resource. My package arrived sooner than expected. All the products are of very good quality. I am very satisfied.
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The objection
This is different from any fasting you have tried before
Most people hear five days and immediately think of hunger, fatigue and white-knuckling through an empty stomach.
With the Prolon 5-Day FMD you eat real food every day. Plant-based soups, bars, snacks, herbal teas and supplements, all pre-portioned and labeled for each specific day.
No meal planning
No measuring
No guesswork
95%
Complete their first cycle
95% of people who try the Prolon FMD complete their first cycle. Most say Days 4 and 5 are the easiest.
The mechanism
"But how is fasting while eating even possible?"
Your body does not know it is fasting because you stopped eating. It knows because of what it stops detecting.
Step 01
Your body reads signals, not plates
Specific nutrients at specific levels are what signal your body that it is fed.
Step 02
Below the threshold, fasting mode switches on
When those signals drop below a certain level, the body shifts state on its own.
Step 03
Prolon holds the signals under it
Precisely engineered to keep those signals below that threshold, with real food on the table.
Nutrient signalling during the five days
So your body stays in a fasting state while you eat real, plant-based food for five days.
After the five days
"What happens after? Will the weight just come back?"
This is where Prolon is fundamentally different from caloric restriction.
Long-term caloric restriction
The metabolism adapts downward
When you restrict calories long-term, your metabolism can adapt downward. The moment you eat normally again, the weight may return, often faster than before.
Prolon 5-Day
A precise five-day biological intervention
Prolon does not work through sustained restriction. It works through five defined days, then you return to eating normally.
Most users say the reset goes further than the weight
Reduced cravings, better appetite awareness, and healthier habits that carry over naturally.
User-reported outcomes. Individual results may vary. Charts are illustrative of the difference described above, not clinical trial data.
Clinical results
What makes Prolon different from anything else on the market
Targets visceral fat specifically
A 12-month randomized controlled trial using MRI measurements found that Prolon participants lost 37.9 cm² of visceral fat, while the control group gained 7.6 cm² over the same period.8
Prolon
−37.9 cm²
Control group
+7.6 cm²
Change in visceral fat area over 12 months, measured by MRI.
Protects lean muscle
Clinically proven to protect muscle. One reason is the L-Drink, engineered to protect lean tissue while your body burns fat, one thing diets and GLP-1 medications were never built to do.9
L-Drink
Included in every kit
Triggers autophagy
In a December 2025 Cedars-Sinai clinical trial, Prolon became the first nutrition program in history measured to activate autophagy, the cellular cleanup process that earned the 2016 Nobel Prize in Medicine, in living humans.10
First
Nutrition program measured to activate autophagy in living humans
Can reduce biological age
After three consecutive monthly cycles of Prolon, participants in a 2024 Nature Communications study showed a median 2.5-year reduction in biological age score.11
−2.5 yrs
Median biological age score, after three consecutive monthly cycles
Day by day
What happens in your body during the 5-Day FMD
Day 1
Glucose stores deplete
Your body begins shifting toward using fat for fuel.
Day 2
Ketosis may begin
Your body may transition into ketosis, using fat as its primary fuel source.
Day 3
Autophagy activates
Cellular cleanup begins.
Day 4
Deep cellular renewal
Many report the sharpest mental clarity they have felt in years.
Day 5
The cycle completes
Autophagy is shown to continue into Days 6 and 7.
Swipe through the five days
By Day 5 users report a difference in their energy, their focus, their relationship with food, and the way their body feels from the inside out. That is what five days of targeting the right fat actually does.
The record
Join 1 million people who have already tried it
25+
Years of scientific research
Decades of studies on longevity and nutrition
47
Clinical trials
Conducted with world-leading institutions
18
Leading research institutions
Including USC, Stanford, Mayo Clinic, and more
200+
Pending or issued patents
For optimizing longevity and healthspan
The Prolon 5-Day FMD is clinically proven to trigger autophagy, while helping you lose visceral fat and protect your muscle.
Five days, planned for you
One labeled box per day. Open it, eat, and let the five days do the work.
Choose your kitStart your five days
Prolon 5-Day Fasting Mimicking Diet
Choose your soups, then choose how often you want them. Every kit contains the full five days, sequenced and labeled by day.
Nutrition
Day 1 around 1,100 kcal, Days 2 to 5 between 700 and 800 kcal. Contains tree nuts (almonds, macadamia, pecans, coconut). May contain soy.
Shipping
Free shipping on continental US orders over $199. Ships in 3 to 5 business days.
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What is in the box
Five daily boxes, each pre-portioned, no prep needed.
Soups
A proprietary mix of all-natural, plant-based ingredients.
Nut bars
Cold-pressed, with almonds, macadamia nuts and pecans.
Snacks
Olives from the South of Spain and kale crackers with plant-based protein.
L-Drink
Proprietary glycerol mix designed to fuel and protect muscles through the fast.
Supplements
Multivitamins, minerals and omega-3 fatty acid.
Herbal teas
Caffeine-free, with antioxidants, to keep you hydrated through the week.
Before you start
Questions people ask first
What is the Fasting Mimicking Diet, or FMD?
A five-day nutrition program where every item is formulated to keep your body in a fasting state while you eat. It was designed and clinically tested to nourish the body while inducing the cellular, metabolic and emotional benefits of prolonged fasting.
How do I use the Prolon FMD?
Five days on, 25 days off. Each day arrives as its own pre-portioned box with soups, bars, snacks, the L-Drink, supplements and teas, so there is nothing to plan, measure or shop for.
Will I lose weight on the program?
Prolon supports fat-focused weight loss while protecting lean muscle. In a 12-month randomized controlled trial using MRI, participants lost 37.9 cm² of visceral fat while the control group gained 7.6 cm². Weight loss depends on individual factors, and the program is designed to protect lean body mass while reducing fat.
Is Prolon safe?
Prolon was designed and clinically tested with global universities and has been validated across more than 47 peer-reviewed clinical studies. Consult your healthcare provider before starting any new nutrition program, especially if you have a medical condition or are taking prescription medications.
Will I feel hungry during the five days?
You eat real, plant-based food every day rather than fasting on water. 95% of people who try the Prolon FMD complete their first cycle, and most say Days 4 and 5 are the easiest.
Tax-advantaged
Can I use my HSA or FSA card?
Yes. Prolon 5-Day is HSA and FSA eligible. Choose to pay with Sika Health at checkout.
How often should I do it?
Optimal results are seen with three consecutive monthly cycles, which is also the protocol behind the 2.5-year biological age finding. After that, most people repeat the cycle periodically through the year.
Five days
Target the fat that matters, and keep the muscle that carries you
The Prolon 5-Day FMD is clinically proven to trigger autophagy, while helping you lose visceral fat and protect your muscle.
From $182.75 with subscribe and save · free shipping over $199 · HSA and FSA eligible
25+ years of research
47 clinical trials
18 research institutions
1 million people
Disclaimer: These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary. Consult your healthcare provider before starting any new nutrition program, especially if you have a medical condition or are taking prescription medications.
Citations
- 1. Visceral Adiposity Index meta-analysis, ScienceDirect
- 2. Removal of visceral fat prevents insulin resistance, Diabetes
- 3. Inflammatory markers and cellular aging, PMC9795790
- 4. Visceral fat and hormonal signalling, PMC3964739
- 5. Visceral fat accumulation with age, PubMed 24834015
- 6. Caloric restriction and visceral fat, Obesity
- 7. GLP-1 and lean mass, PubMed 38629387 and PubMed 40289060
- 8. 12-month randomized controlled trial, MRI visceral fat, PubMed 40425403
- 9. USC phase II clinical trial, PR Newswire
- 10. Cedars-Sinai autophagy trial, GeroScience 2025
- 11. Biological age reduction, Nature Communications 2024
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