By Amy Burkhart, MD, RD | Dr. Burkhart is the only physician in the United States who is also a registered dietitian and board-certified in integrative medicine.

What Is the Fasting Mimicking Diet?

Most people think fasting means going without food entirely, but the ProLon Fasting Mimicking Diet turns that assumption on its head, with science backing up the claims.

The ProLon FMD is a clinically developed 5-day program that delivers the benefits of fasting while still allowing you to eat. It is not a liquid cleanse or a severe caloric-restriction protocol, but is a structured, food-based program with real science behind it.

Is There Research Supporting the Fasting Mimicking Diet?

Yes, and it’s substantial. There are nearly 240 completed or ongoing studies examining how the fasting-mimicking diet affects the body. Thus far, the research has identified a range of important health benefits:

• Support for autoimmune conditions
• Measurable improvements in depression symptoms
• Rebalancing of the gut microbiome
• An estimated increase in healthy lifespan of up to 2.5 years
• Anti-cancer cellular activity

This isn’t a wellness gimmick. The ProLon fasting mimicking diet is built on decades of longevity research originating in Dr. Valter Longo’s lab at the University of Southern California, one of the most-cited research programs in the science of aging.

How Can You Eat and Still Be Fasting?

It’s the question everyone asks.

Traditional fasting requires complete food avoidance, which comes with a predictable set of side effects: persistent hunger, low energy, headaches, and difficulty sustaining the protocol long enough to capture its benefits. Most people abandon it before the biology has a chance to kick in.

The fasting mimicking diet takes a different approach. Through a specific combination of plant-based foods, precise caloric targets, and carefully controlled nutrient ratios, the ProLon program keeps the body’s nutrient-sensing pathways in a fasted state even while food is being consumed. The body essentially doesn’t register that it has been fed, so the cellular processes triggered by fasting continue uninterrupted.

The result: you get the benefits of fasting with significantly fewer of the physical downsides that make traditional fasting so difficult to maintain.

What Makes ProLon Different From Other Fasting Approaches?

The ProLon fasting mimicking diet is the only program of its kind specifically designed to activate fasting biology without requiring complete food elimination.

*Dr. Burkhart does not work for ProLon. This is an independently written article.

How Can You Eat & Fast at the Same Time?

• The fasting mimicking diet was developed by Dr. Valter Longo, a longevity researcher who has spent more than 20 years studying fasting, aging, and disease. His research team at the University of Southern California focuses on how the body responds to nutrients, specifically through what are known as nutrient-sensing pathways.
• Instead of complete food avoidance, the fasting-mimicking diet uses specifically formulated, plant-based meals that provide some calories while keeping the body in a fasting-like state by avoiding activation of nutrient-sensing pathways. 

What Are Nutrient-Sensing Pathways, and Why Do They Matter?

Nutrient-sensing pathways function like biological gauges. After a typical meal, these pathways detect the incoming nutrients and signal the body that it’s in a “fed state”, activating processes associated with growth, energy storage, and cell replication.

The ProLon fasting mimicking diet is engineered to stay below the threshold that triggers these signals. Through a precise combination of caloric content, macronutrient ratios, and plant-derived ingredients, the body never receives a clear “fed” signal. The result: metabolic activity continues to mirror a fasted state, even with food present.

The FMD and Autophagy: Your Body’s Built-In Cleaning System

One of the most important factors keeping nutrient-sensing pathways quiet is the amplification of autophagy, the body’s internal process for breaking down and recycling damaged, dysfunctional, or aging cells.

Autophagy is always running at a baseline level, acting as a continuous maintenance crew for your cells. Think of it as a garbage truck operating inside every cell, collecting cellular debris, clearing out worn-down proteins, and making room for healthier structures to take their place.

When the FMD suppresses nutrient-sensing activity, autophagy shifts into a higher gear. This accelerated cellular housekeeping has meaningful implications:

• Damaged cells that contribute to chronic disease and accelerated aging are cleared more efficiently
• The cellular environment becomes less hospitable to the conditions that allow cancer cells to persist
• Overall cellular function improves, which translates to measurable effects on energy, recovery, and long-term health

In short, when your cells clean better, your body operates better, and your risk profile for future disease shifts accordingly.

A Fasting Mimicking Diet Is Specifically Designed

On a fasting mimicking diet, you eat a precise combination of plant-based foods, including soups, crackers, and nutrition bars specifically formulated to keep the body in a fasting state while still consuming real food. All meals and snacks come exclusively from the ProLon kit, the only clinically researched fasting mimicking diet program currently on the market.

Each day’s food is pre-portioned and organized in numbered boxes (1–5), removing any guesswork from the process.

Fasting Mimicking Diet Food List by Day

Day 1 — ~1,100 calories:

• Plant-based soups
• Nut-based crackers
• Nutrition bars
• Plant-based protein, healthy fats, and low-carbohydrate sources

Days 2–5 — ~725 calories per day:

• The same categories of food as Day 1, in smaller portions
• Calorie and nutrient ratios are maintained to maximize autophagy effects

Why You Can’t DIY a Fasting Mimicking Diet

Simply cutting calories does not replicate the fasting mimicking diet. The ProLon kit’s exact macronutrient ratios and food combinations are the product of extensive clinical research. A homemade version has not been validated and will not produce the same cellular effects, including autophagy.

How to Get the Fasting Mimicking Diet Kit

The ProLon fasting mimicking diet kit is available without a prescription and ships directly to your door. For optimal results, complete the 5-day program once a month for at least 3 consecutive months.

The fasting mimicking diet (FMD) is a 5-day program, typically repeated monthly.

Initial phase (months 1–3): The Prolon research team, the primary group behind FMD clinical research, recommends completing the 5-day plan once per month for 3 to 8 months. The majority of published FMD research is based on this 3-month repeating cycle.

Maintenance phase (ongoing): After completing the initial protocol, practitioners generally follow the 5-day cycle every 1 to 6 months, depending on individual health goals, to sustain the diet’s benefits over time.

Why 5 days? The 5-day duration is specifically designed to trigger autophagy, a cellular “self-cleaning” process in which the body breaks down and recycles old, damaged, or dysfunctional cells while preserving lean muscle mass. This distinguishes FMD from standard caloric restriction or prolonged fasting, which can degrade muscle tissue.

Quick reference:

• Program length: 5 days
• Initial frequency: once per month for 3–8 months
• Maintenance frequency: every 1–6 months
• Primary mechanism: autophagy with muscle preservation
• Most studied protocol: 3-month consecutive cycle

The 5-day Prolon Kit Available Here.

• Prolon Discount & cost-saving tips are found here.
• The ProLon Fasting Mimicking Diet is the only fasting-mimicking meal program currently undergoing clinical trials. Clinical studies on fasting-mimicking diets are done with the ProLon kit. Research suggests using the kit once a month for 3 months to achieve optimal results.

A DIY fasting mimicking diet is not the same as the clinically researched Fasting Mimicking Diet (FMD). While numerous DIY versions circulate online, none have been scientifically validated to produce the same metabolic and cellular effects as the official ProLon protocol.

Why DIY Fasting Mimicking Diet Versions Fall Short

The official fasting mimicking diet is backed by over 20 years of research and is precisely engineered with specific vitamins, nutrients, and macronutrient ratios to keep the body in a metabolic fasting state. This level of formulation cannot be replicated by simply reducing calories or following a generic low-calorie meal plan.

A DIY fasting mimicking diet may still offer some health benefits — eating fewer calories and prioritizing whole foods is generally positive — but those results are not equivalent to the proven outcomes of the scientifically formulated FMD protocol. Equating the two is not scientifically supported.

What Makes the Official Fasting Mimicking Diet Different From a DIY Version?

Should You Try a DIY Fasting Mimicking Diet?

If the cost of the ProLon kit is a barrier, a low-calorie, whole-food diet may still support general health improvements. However, to experience the full, proven benefits of the fasting mimicking diet — including autophagy and cellular renewal — the official ProLon kit is currently the only validated option. Research on standardized DIY versions is ongoing and may provide more guidance in the future.

Intermittent fasting (IF) and the fasting mimicking diet (FMD) are two distinct approaches to fasting — they work differently, serve different purposes, and should not be used interchangeably.

What Is Intermittent Fasting?

Intermittent fasting involves cycling between designated periods of eating and not eating throughout the day. It does not prescribe specific foods — it prescribes timing.

The most common IF protocols include:

16:8 method — the most popular approach. Individuals fast for 16 consecutive hours, consuming only calorie-free beverages such as water or plain tea, followed by an 8-hour eating window. Food choices during the eating window focus on healthy options without strict calorie counting. The timing windows are flexible, but maintaining a continuous 16-hour fast is essential.

5:2 method — individuals eat normally five days per week and fast completely for two non-consecutive days, consuming only water or calorie-free beverages on fasting days.

How Is the Fasting Mimicking Diet Different From Intermittent Fasting?

The fasting mimicking diet works through an entirely different mechanism. Unlike intermittent fasting, the FMD does not rely on timed eating windows or periods of complete food restriction. Instead, it uses a precise combination of real food — carefully formulated to keep the body in a fasting state metabolically — while allowing controlled calorie intake across five consecutive days.

The key distinction: intermittent fasting controls when you eat. The fasting-mimicking diet controls what you eat and, in what precise combination, to trigger fasting biology without abstaining from food entirely.

• Click these links to see the completed research and ongoing research.  Currently, many projects are in progress looking at the effects of FMD on conditions such as autoimmunity, longevity, cancer, fertility, inflammation, weight loss, and more.
• Below is some of the research done on common conditions.

Prolon FMD & Depression

A study showed that using a fasting-mimicking diet in conjunction with therapy for depression resulted in significantly better outcomes than therapy alone.

Fasting Mimicking Diet & Aging

A 2024 study in Nature showed remarkable results regarding the FMD’s effect on diet and aging.  Three rounds of the FMD lowered the biological age by 2 1/2 years compared to the actual age. More studies are needed but it may get us one step closer to a fountain of youth.

Fasting Mimicking Diet & Weight Loss

A large randomized trial* compared FMD with a typical calorie-restriction regimen. Both approaches achieved comparable weight loss and improvements in risk factors for cancer, diabetes, and cardiovascular disease. Both appeared equally beneficial for weight loss and disease risk reduction. *human study

Fasting-mimicking Diet & Multiple Sclerosis

All mice had improved symptoms, and 20 percent of mice with MS had complete resolution of symptoms. No meds, no side effects! The FMD reduced markers of inflammation and promoted a healthier gut microbiome.

FMD Improves Sense Of Smell & Taste

A 2025 study showed significant improvement in the sense of taste and smell, which is often decreased in obesity.

FMD & Parkinson’s Disease

In this animal study, the fasting-mimicking diet was helpful in improving Parkinson’s disease symptoms and slowing disease progression.

Alzheimer’s & FMD

The results of this animal study show that periodic protein restriction cycles protect against age-related changes.  A 2023 study on the FMD and Alzheimer’s showed improvement in cognitive function, biomarkers and well being in Alzheimer’s patients when using the FMD.

FMD & Diabetes

In this human study, FMD was found to help blood glucose control in type 2 diabetics.

Inflammatory Bowel Disease & FMD

The fasting-mimicking diet decreased gut inflammation and increased the number of stem cells and the number of “good” gut bacteria in people with inflammatory bowel disease. A 2026 study in patients with Crohn’s and the fasting mimicking diet showed it to be superior to a regular diet in helping control Crohn’s and promote remission.

Cancer & FMD

Can a fasting-mimicking diet help in the fight against cancer? That can’t be said yet, but early results are promising. One research study in mice found that a fasting-mimicking diet could reverse tumor growth. Yes, this is in mice, but wow! Couldn’t this be a fantastic addition to cancer therapy if it pans out in humans? A 2024 study on the FMD and CLL shows promising results for the most common leukemia in adults.

Other studies have looked into how fasting-mimicking diets might work on people with cancer, but they are still preliminary, and more research needs to be done before we can say for sure. See the bottom of this article for other studies on FMD and cancer.

Fasting Mimicking Diet Wrap-up

• The fasting-mimicking diet is a specific meal plan formulated to simulate the fasting state while providing some nutrients and calories. It does this by not triggering pathways that make the body think it is in a fed state.
• The fasting-mimicking diet is not the same as restricting daily calories.
• The FMD appears to be as effective as calorie restriction for weight loss. More studies are needed, of course.
• Many human trials are in progress using the fasting-mimicking diet for various health conditions.
• The diet has the potential to provide an alternative to more restrictive forms of fasting.
• The FMD aims to provide the benefits of fasting without the common side effects, such as headaches, fatigue, and muscle loss.
• In my clinical experience with the FMD, I have seen patients have improvement in digestive and autoimmune conditions, energy levels, mood, inflammation, and sleep.
• If you are considering the fasting-mimicking diet, please consult a medical professional before you begin. Fasting is not appropriate for everyone. Learn here: who should not fast?

Listen here to a PODCAST on the fasting mimicking diet with Dr. Valter Longo.

Body Of Wonder Podcast Featuring Dr. Andrew Weil and Dr. Victoria Maizes

This is a fantastic podcast covering research-based topics in the field of integrative medicine.

• Cyclic Fasting-Mimicking Diet in Cancer Treatment: Preclinical and Clinical Evidence
• Effect of Fasting-Mimicking Diet on Markers of Autophagy and Metabolic Health in Human Subjects
• Effects of the Periodic Fasting-Mimicking Diet on Health, Lifespan, and Multiple Diseases: A Narrative Review and Clinical Implications
• Fasting-Mimicking Diet Causes Hepatic and Blood Markers Changes Indicating Reduced Biological Age and Disease Risk
• Fasting Mimicking Diet During Neo-Adjuvant Chemotherapy in Breast Cancer Patients: A Randomized Controlled Trial
• Fasting Mimicking Diet Extends Lifespan and Improves Intestinal and Cognitive Health
• Fasting Mimicking Diet for Metabolic Syndrome: A Narrative Review of Human Studies
• Fasting-Mimicking Diet Modulates Microbiota and Promotes Intestinal Regeneration to Reduce Inflammatory Bowel Disease Pathology
• Fasting-Mimicking Diets Reverse Accelerated Biological Aging in Multiple Sclerosis
• Fasting Mimicking Diet and CLL
• Fasting Mimicking Diet and Aging
• Fasting Mimicking Diet and Weight Loss
• Fasting Mimicking Diet and Metabolism
• Fasting Mimicking Bar Extends Ketosis
• Fasting Enhances the Response of Glioma to Chemo- and Radiotherapy
• FMD Decreases the Inflammatory Response in Autoimmune Disease
• FMD Improves Response to Breast Cancer Chemotherapy
• Impact of Fasting Mimicking Diet on Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Control Trials
• Integration of a Fasting-Mimicking Diet Programme in Primary Care for Type 2 Diabetes Reduces the Need for Medication and Improves Glycaemic Control: A 12-Month Randomised Controlled Trial
• Neuroprotection of Fasting Mimicking Diet on MPTP-Induced Parkinson’s Disease Mice via Gut Microbiota and Metabolites