Fasting Mimicking Diet: Expert Review, Common Mistakes & Guidelines

Heidi Moretti Author circleHeidi Moretti, MS, RD
Certified Clinical Dietitian
Anti-Aging Researcher

Research | Meals | Foods to eat | Benefits | Side effects | My experience | Tips & MistakesAfter the Fast | Cost

I have recently done Dr. Valter Longo’s proLon fasting mimicking diet (FMD), for the second time.

In this review, I will share my personal experience, thoughts, important guidelines and common mistakes I often see, to help you better decide if this diet is for you. I highly recommend that you go over my notes in this guide before you start the ProLon diet.

If are currently doing my longevity protocol for graceful aging:

  • The main difference between my protocol and the proLon fasting mimicking diet is that the diet is a short term 5-day plan. My protocol on the other hand, is intended for long term.
  • I see both as effective tools that can compliment each other and help us all optimize our health and lifespan potential.
  • My longevity protocol can be very helpful to do between your ProLon diet cycles.
Fasting Mimicking Diet Product 1
The ProLon Fasting Mimicking Diet
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The Fasting Mimicking Diet: What’s The Bottom Line?

The fasting mimicking diet has pros and cons.

Anti-aging Perspective: Safe, Effective, Easy To Do

The diet is clinically shown to mimic two of the most powerful most studied longevity promoting dietary regimens: fasting and calorie restrictions.

Practicing long term fasting and calorie restrictions is extremely difficult.
As a result, most people will never do any of these.

The proLon fasting mimicking diet was invented to solve this exact challenge.

The ProLon diet is very practical and easy to do, allowing you to get the same anti-aging and longevity benefits shown in the clinical studies, without having to actually fast or worry about nutritional deficiencies.

proLon fasting mimicking diet box

What’s Inside?

The proLon Kit comes with five small boxes, one for each day, with everything you need to eat and drink. Meals, drinks, snacks, bars, supplements, everything was already made for you. It’s really that simple.

So if your goal is to promote healthy longevity and anti-aging, the fasting mimicking diet may be a really great fit. 

Healthy Weight Loss & Metabolic Health

Another area I believe the fasting mimicking diet may help, is to promote healthy weight loss and metabolic health.

In the clinical studies, FMD was shown to help individuals with normal BMI to lose an average of 5.7 lbs of fat and 1.2 inches off waist circumference.
Effects persisted after returning to normal diet.

This is actually a huge benefit since high fat accumulation around the waist is a risk factor for heart disease and type 2 diabetes.

I actually noticed it myself (see my full review below). In only 3 days, I lost 5 lbs, which amazingly didn’t come back after resuming my normal diet.

I definitely saw significant stubborn belly fat loss. It was apparent and I am very impressed by this considering that I didn’t have much body fat to begin with.

Fasting Mimicking Diet: Can You Eat & Fast At The Same Time?

ProLon Fasting Mimicking Diet Eat & Fast At The Same Time

Have a look at the image above, as this can give you an idea of the nutrients you will be getting in a typical 5 day ProLon fasting mimicking diet plan.

The inventor and brain behind the FMD is Dr. Valter Longo, director of Longevity Institute at the University of Southern California.

Dr. Longo is one of the world top anti-aging experts. Myself just like many of my coworkers have been following his work for years.

The idea is simple. For five days you eat and drink scientifically researched meals and drinks in precise quantities. These nourish you, but are not recognized as food by your body, therefore mimic a fasting state.

The calories are still very low, so you basically get the benefits of fasting and calorie restriction while still eating a balanced meal plan. As a part of the ProLon diet plan, supplements are also included.

Can You Eat & Fast At The Same Time? How is it Even Possible?

Dr. Longo work has shown that when we consume certain foods and natural ingredients, our body still acts as it didn’t get food. As a result, the body activates the same longevity genes that are triggered during prolonged fasting.

These are exactly the ingredients you will find in the Prolon fasting mimicking diet.

That, in my opinion, is what makes the diet so promising.

I know most of my clients will never agree to do prolong fasting.
But what about trying
the 5-day ProLon plan? Eating mediterranean style soups, crackers, olives and chocolate-nut bars for a few days to reboot their system and rejuvenate? Completely different story.

Fasting Mimicking Diet Benefits

Fasting Mimicking Diet Benefits

The ProLon Fasting Mimicking Diet
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The ProLon Fasting Mimicking Diet has gone through clinical trials and been patented for its healthy aging effects.

The results have been published in top medical journals (Cell, Science Translational Medicine, JAMA, etc.) According to the studies, three cycles of the 5-day FMD plan have been shown to:

  • Reduce visceral fat, but at the same time, maintaining lean body mass
  • Initiate autophagy and cellular clean up
  • Decrease IGF-1, which has been linked to aging and disease
  • Help maintain metabolic health

Pretty impressive considering that you only have to do the diet five days per month for three months. I personally noticed the reduced belly fat after only three days. See my complete review and results below.

So, if you wonder how often can you do the fast mimicking diet, ideally, you should stick with what was done in the study. Five Days per month, for three months.

What Do You Eat on ProLon Diet?

What Do You Eat on ProLon Diet

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The above pic shows a typical day of eating on the ProLon fasting mimicking diet. FMD is based on a combination of mediterranean style plant-based soups, crackers, olives, drinks and teas.

  • Soup blends: Minestrone soup, mushroom soup,  minestrone quinoa soup, tomato soup, vegetable soup, butternut squash – quinoa soup, white bean – spinach soup, and butternut soup squash soup.
  • Bars: chocolate crisp bar, nut-based bar
  • Olives: flavored with and without garlic
  • Kale Crackers: with flax seeds,  sunflowers seeds, sesame seeds, hemp seeds, and pumpkin seeds.
  • Energy drinks:  also called L-drink, caffeine free, orange and berry flavors
  • Herbal teas: hibiscus tea, spearmint tea, spearmint-lemon tea
  • Supplements: multi vitamin & mineral, omega 3 DHA from algal oil.

When ordering, remember to choose the options you prefer the most under flavor. (Original and Soup Variety 2).

ProLon Diet 5-Day Meal Plan

ProLon Diet 5-Day Meal Plan
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ProLon Fasting Mimicking Diet: Taste & Feel

ProLon Fasting Mimicking Diet Taste

People usually find the taste of the meals to be pleasant. I personally enjoyed the meals and drinks and liked how they made me feel.

With that said, I did feel like I wouldn’t mind to have some extra protein with the meals. Nothing major, and to be expected. This is one of the core ideas behind the diet. To promote autophagy, the diet per design has to be low in protein.[5] Animal proteins can stimulate an increase in IGF-1, so this is why they are eliminated during the 5 day period.

My Fasting Mimicking Diet Review

My Fasting Mimicking Diet Review

I have done the fasting mimicking diet twice, about 6 months apart.
I decided to stop after day 3 both times because I didn’t want to lose more weight. My weight is at baseline is pretty low.

Overall, I was surprisingly not that hungry until day 3. It actually felt good to have a less full stomach. My meals tasted good, and I was happy and satisfied. Like I mentioned earlier, I felt I could have more protein, though.

How much weight can you lose on the fasting mimicking diet?

In only 3 days, I lost 5 lbs each time, which amazingly didn’t come back after resuming my normal diet. I definitely saw significant stubborn belly fat loss. It was apparent and I am very impressed by this considering that I didn’t have much body fat to begin with.

Energy, brain function & mood

Overall, I felt fair energy and was able to do yoga.  I didn’t feel up to heavy exertion.

My brain function and focus were actually great. I was focused on what to eat and not on other things in my life. It’s a relaxed state of mind I really like. This by itself, is one reason I want to do the ProLon diet again.

By the second day, I felt a little bit of a lull in brain function.  I struggled to find the energy for work a bit. Nothing major, though. I was still able to function well. My mood was fairly good, although on day 3 I had a mild headache which did affect my mood a bit.

Fasting Mimicking Diet: Cost

Fasting Mimicking Diet Product 1
The ProLon Fasting Mimicking Diet
Check Price & Availability

The fasting mimicking diet cost is around $250, or less if you order 3 boxes (see ProLon website for all pricing options).

This includes all the foods, drinks and supplements you need for the five days fasting, minus the water.

As a reference, the average American spends around $150 on food per week. One in 10 Americans say they spend $300 or more per week.[6].

And that doesn’t include weight loss or anti-aging shakes, supplements or other specialty foods. So, not that far.

Keep in mind, anti-aging and weight loss is a billion dollar industry. This is a drop in the bucket compared to most fad diets, risky weight loss pills, or anti-aging products that have no science behind them. The ProLon fast mimicking diet plan has research on its effectiveness and safety, with an army of medical doctors who back it up and recommend it to their patients.

You can read the reviews on ProLon website.

FMD: Common Mistakes to Avoid & Tips

In the section below, I will try to address some of the top questions and mistakes I see people make.

During the fast

You will want to drink water or the FMD teas and skip caffeine and coffee if you can. One cup of black coffee is fine and may even help to promote autophagy further according to some evidence.[7

You can add in a bit of extra spices and herbs, but no more than a teaspoon total of salt, herbs, and spices. Try not to add salt if possible, as you don’t want to get your taste buds get used to salty foods. This can create a problem after the fast.

In general, since ProLon fast mimicking diet has been studied on humans, it is probably best to stick to the plan as closely as possible.

What to Eat After the Fasting Mimicking Diet

ProLon Longevity Diet Shopping List

A common mistake I often see people make after a fast, is to eat a lot of calories, thinking that the body may need the extra foods to rebuild. This however, has proven to backfire. In fact, it is very important to gradually return to normal eating, starting with light meals. This can help your body to digest your foods, save you a lot of problems and can further augment your results after the five days of eating the ProLon diet.

Probiotics & Enzymes: Many people can benefit from taking digestive enzymes and probiotics with their meals a few weeks after the fast, to help the body digesting solid meals again.
Dr. Group Veganzyme and Floratrex are excellent choices.

Eat Clean: I can’t stress this enough:

A lot of the benefits of fasting happen after the fast when you start to refeed. Think about the new fresh cells and stem cells in your body ready to grow and thrive with the foods you eat. It is a window of opportunity to eat clean and healthy, to provide your body the best possible nourishment.

As I mentioned earlier, my longevity protocol can be very helpful to do between your ProLon diet cycles.


  • Gradually introduce foods back, keep it light and mainly plant-based
  • Focus on healthy whole foods
  • Avoid processed foods and drinks
  • Keep sugars low
  • Limit meat, fish, dairy, and other animal products
  • Eat healthy amounts of good fats such as olive oil, nuts, and avocados
  • Eat colorful fruits and vegetables. These are packed with antioxidants and phytonutrients shown to promote good health and longevity.

ProLon Longevity Diet Shopping List

ProLon Longevity Diet Shopping List
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5 from 5 votes

ProLon Longevity Diet Shopping List

Suggested options for healthy longevity promoting foods you can eat after the fasting mimicking diet
Course Fasting Mimicking Diet
Cuisine Mediterranean
Keyword Fasting Mimicking Diet
Cook Time 25 minutes
Servings 1
Author Heidi Moretti, MS, RD


Eat the Rainbow: White

  • Leeks
  • Garlic
  • Onion
  • Cauliflower
  • Mushrooms

Eat the Rainbow: Red

  • Beets
  • Red Peppers
  • Organic Strawberries
  • Cranberries

Eat the Rainbow: Yellow & Orange

  • Butternut Squash
  • Carrots
  • Yellow Peppers
  • Pumpkin
  • Lemons
  • Sweet Potatoes

Eat the Rainbow: Green

  • Broccoli
  • Kale
  • Bok Choy
  • Cabbage
  • Brussel Sprouts
  • Cucumbers
  • Celery
  • Green Peppers
  • Zucchini
  • Avocado
  • Olives
  • Lime

Eat the Rainbow: Blue & Purple

  • Purple Cabbage
  • Eggplant
  • Organic Blueberries
  • Blackberries

Healthy Fats: Eat in Moderation

  • Olive oil
  • Macadamia nuts
  • Cashews
  • Pumpkin seeds
  • Almonds
  • Pecans
  • Walnuts

Healthy Complex Carbs: Eat in Moderation

  • Legumes
  • Quinoa
  • Steel cut oats
  • Brown rice

Seafood: Eat in Moderation, 2-3 times a week

  • Wild Caught Salmon
  • Sardines
  • Cod

Fresh Herbs & Spices

  • Basil
  • Fenugreek
  • Thyme
  • Sea Salt
  • Bay leaves
  • Saffron
  • Turmeric
  • Paprika
  • Black pepper
  • Cayenne
  • Ginger
  • Raw Unpasteurized Apple Cider Vinegar


  • Choose the foods you enjoy the most from each group to support healthy longevity between ProLon fasting mimicking diet cycles.
  • If you follow low carb, you don't have to choose from the complex carbs group, and replace with more good fats

Fasting Mimicking Diet Side Effects

I find that the side effects on the proLon diet depends on your starting point. In other word, what was your diet before. The cleaner and healthier, the better.

ProLon diet is actually well tolerated by most people. Common complaints reported in the clinical trial were fatigue, headache, and difficulty with concentration. With that said, these were mild and most people could continue with the diet.

In my case, by day three, I certainly had a headache. Nothing major, though. Keep in mind, this may be a sign that your body is eliminating toxic compounds. People usually find that the headache is temporary and goes away by day four.

Who Shouldn’t Do The Fast Mimicking Diet

The fasting mimicking diet is gluten free and lactose free.
With that said, it does have a few ingredients that some people may prefer not to consume:

  • Nuts & Soy Intolerance. The bars contain nuts, and there are small amounts of soy. So people with allergies or sensitivities to tree nuts or soy should probably not do the diet.
  • Vegans: FMD is plant based. But, the bars have honey, and the supplements capsules are made from gelatin.

Also, FMD is probably not for you if:

  • You are at a low body weight: considering that you are likely to lose more weight during the diet.
  • You have a medical condition or take medication: your body behaves differently during the fast, which can affect your condition or the way the medication works. Always speak with your doctor before you start the ProLon diet.
  • Pregnant & breastfeeding are times where you need to nourish your body, not fast.

My Final Thoughts

As you can see, the fasting mimicking diet has pros and cons and it is not for everyone.

I find the research and science behind it encouraging. I think the ProLon fast mimicking diet may be a really good options if your goals are:

Anti-aging & longevity: FMD offers some of the most powerful anti-aging and longevity benefits without you having to actually do a long term fast or calorie restriction.

Healthy weight & metabolic balance: In addition to the initial weight loss, FMD can help regulate some of the key factors that influence your metabolic health.

Caloric Restriction & Fasting: Mother’s Nature Anti-aging Clinic

Caloric Restriction & Fasting: Mother's Nature Anti-aging Clinic

A quick summary of the science behind the fasting mimicking diet.

In my longevity protocol for graceful aging, we looked into the benefits and pitfalls of two of the most powerful, most studied anti-aging dietary regimens: fasting and calorie restriction.

The research data on both sounds almost too good to be true.

  • Extend Lifespan. Multiple studies have shown that a 20 – 50% reduction in caloric intake was able to extend lifespan by up to 50%.[1].
  • Activate Autophagy. As if that’s not impressive enough, prolonged fasting was shown to activate potent longevity pathways including autophagy.
    Autophagy is the process where the body recycles damaged and dysfunctional cells, in order to regenerate newer, healthier cells.[2].
  • Produce Stem cells. As a part of the response to fasting, the body also produces stem-cell to promote stress resistance, self-renewal and regeneration. Stem cells have the ability to develop into many different cell types. The body can use them as a renewable source of replacement cells and tissues.[3,4

Fasting Mimicking Diet: Solving the Pitfalls of Fasting & Calorie Restriction

If you have ever tried to fast for a few days or cut 30% of your caloric intake, I am sure you noticed that this can be extremely difficult.

In fact, most people will not do it. Even me, as an anti-aging researcher that is determined to extend my life as much as possible, find it very hard.

So despite all this exciting data and research about the benefits, the bottom line for most people: fasting and calorie restriction are just not realistic.

There’s more here than just willpower.

We are not lab rats. There’s much more in our lives than running on a treadmill in a lab. With less calories or food, our brain eventually goes into “preservation” survival mode. When this happens, you may lack the needed motivation to thrive and reach your full potential. You may live longer, but, I doubt many people will find that type of life appealing.

Even if you can function, you really need to know what you are doing. Long term fasting or calorie restrictions can lead to serious nutritional deficiencies.

This in a nutshell, is what the fasting mimicking diet is trying to solve.

Heidi Moretti, MS, RD
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4 Replies to “Fasting Mimicking Diet: Expert Review, Common Mistakes & Guidelines”

  1. 5 stars
    If are currently doing my longevity protocol for graceful aging:

    The main difference between my protocol and the proLon fasting mimicking diet is that the diet is a short term 5-day plan. My protocol on the other hand, is intended for long term.

    I see both as effective tools that can compliment each other and help us all optimize our health and lifespan potential.

    My longevity protocol can be very helpful to do between your ProLon diet cycles.

  2. 5 stars
    Solid review.

    I’ve done the Prolon 5 day Fasting Mimicking diet 3 times I’ve the last 18 months and am on my fourth round. The first three times were 4-6 months apart. This time I’m doing it within a month of the last one and plan to do another round in a month.

    I usually lose 7-11 lbs of mostly fat on each round. On the longer gaps my weight usually starts to creep up to close to the starting point towards the end of the 4-6 months. I’m hoping doing 3 sessions back to back will help me get to a new set point.

    I was 265lbs at 40. Switching to a mostly plant based diet and increasing activity got me to a set point of 220-230lbs by 43. I’m currently 45 and with prolon I’ve been hovering between 215-225 over the last 18 months. Hoping the consecutive months will get me consistently under 210.

    Probably more importantly than just the weight loss, I ALWAYS feel better in the initial months after doing the fasting mimicking diet, with more energy and better thought clarity.

    I will be looking into your protocol to help me continue to make improvements over the upcoming months & years.

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