The Fasting Mimicking Diet – What’s it About?

You may have heard about the Fasting Mimicking Diet (FMD), promoted by Professor Valter Longo, author of The Longevity Diet. Longo’s research is all about aging – and more importantly, how to slow it down.

Although Longo studies centenarians – those who live over 100 years – his focus goes beyond how many years you can add to your life. Why drag yourself to your 100th birthday with the diseases that typically come with aging (think heart disease, diabetes, arthritis, dementia, Parkinson’s, cancer, etc.)? Longo focuses on preventing these diseases. In other words, aging with vibrant health and vitality.

Who doesn’t want this? Many of us see our beloved elders rapidly decline as they age. Many of my patients at a certain age (often as young as 50!) say things like:

  • This aging stuff is for the birds!
  • Aging sucks! Don’t do it.
  • I know this (fill in the blank) disease is just a part of aging. Runs in the family.

Do you actually have a choice about how you age? Are all the “aging diseases” truly preventable? According to Longo’s research and those behind the FMD, the answer is yes! The science is there and it makes good sense.

My friends are doing it

This year (2018) I’ve watched my colleagues use the FMD with their patients, primarily to shake up metabolic syndrome and resistant weight loss – with great success. People lose weight, change their hunger signals, improve their labs (cholesterol, triglycerides, and inflammatory markers), and their body composition. And the good news is these changes stick after the five-day fast.

How does the FMD work?

The beauty is that it is designed (and proven) to reap all the benefits of fasting, but you still get to eat. You eat specific macronutrients in measured amounts for five days. This approach is easier than fasting with no food. In fact, fasting with no food can cause a breakdown in body tissue you don’t want to lose! The FMD preserves important tissue like muscle, and gets rid of the crappy stuff – stored fat and cellular garbage.

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ProLon® is the prepackaged version of the FMD that replicates Longo’s research to the tee. You get a slick white box that looks like a new Apple computer. Inside are five individual boxes that contain high-quality organic food for each day. The best part is that ProLon® is all dialed in – no thinking, planning, shopping, chopping or cooking. You can do a homemade version as well – which is great for people with dietary restrictions.

The research supports doing the FMD once per month for three months. However, variations include twice a year, once per season, and even once a month for a year for stubborn conditions.

So what ARE the benefits of fasting?

The researched benefits of controlled fasting – NOT starving – are compelling. Fasting induces a process called autophagy (literally self-eating). This is when your cells get rid of damaged organelles, misfolded proteins (think cancer) and invading microorganisms (think chronic infections and pathogens).

It’s all about autophagy

Documented and well-researched results of the FMD that continue after the five days include:

  • Loss of abdominal (belly) fat – a dangerous metabolically active type of fat.
  • Lowered cholesterol.
  • Improved insulin sensitivity.
  • Reduced inflammation.
  • Increased stem cell production and regeneration of tissue.
  • Improved stress resistance.
  • Protection against age-related degeneration such as cardiovascular disease, diabetes, hypertension, cancer, and neurodegeneration (think dementia and Alzheimer’s).

There are many approaches to fasting – for example, you may have heard about intermittent fasting which is all the rage. The fasting mimicking diet is a bit different, because you actually get to eat AND get the benefits of fasting. How do we know this? There’s a huge amount of research behind it. In fact there’s more research behind this approach then there is behind intermittent fasting. 

The FMD is easier to do than other forms of fasting and actually gets better results with all of the above markers. Check out this comparison chart:

intermittent fasting, functional medicine, laura paris, fasting mimicking diet, longevity diet, homemade fasting mimicking diet, paleo

My own home experiment

Fall, 2018

So, my adventurous partner Seth and I decided to try the FMD ourselves, as I like to do with most things before recommending them to patients. The science is there. The logic is there. But I wanted to know how it actually FEELS to do it! Here’s our story . . .

Day 1

I have to admit, having everything ready-made was super appealing. We didn’t have to think about it or do any work. Our first vegan day in years! Confession: we had a smidgen of coffee in the morning, which is allowed “if needed.” We needed. Since we decided to do this, I’ve learned of two women who got rid of their Hashimoto’s thyroiditis by fasting, one of them with ProLon. I’m pretty excited to see what happens, and look forward to the metabolic shakeup.

Day 1 was bearable, however we were tired, hungry and a tad grumpy.

Day 2

Seth woke up feeling great. His energy was better compared to day one, even though calories dropped from 1075 on day 1 to around 700. He was even able to grocery shop for our ravenous teenager and not die of fatigue or hunger.

Me, however – different story. I woke up FULL of histamine reactions (stuffed nose, puffy eyes, wheezing, headache), joint and muscle pain, and a heavy fatigue. I felt like I got hit by a truck.

Why the difference? I reacted to the packaged food ingredients (drat!) due to a long term struggle with food intolerances. The culprits were in most of the foods: yeast, garlic, and onion powder. I took my killer natural anti-histamines and recovered. But what to do? Continue or not?

We decided I should shift to a quick makeshift homemade version of the FMD with my “safe” foods. I felt much better, but I was jealous of Seth’s white boxes and no work.

Day 2 was easier even on less food. Our minds were clear and we were slightly tired, but not hungry or grumpy.

Day 3

As you can see from this video, Seth felt great. By the way, this is shocking, as he normally has the need-to-eat-frequently kind of metabolism. He tried “muscle-ups” in the park for the first time in a couple of years. 

I continued with my homemade version, and sorry, no muscle-ups. I had lots of noise and rumbling in my intestines which actually felt really good. It could mean my migrating motor complex (waves of small intestine muscular movement that only happen on an empty stomach, and often damaged with SIBO) was waking up.

Day 3 we were fully in the appetite suppression stage of fasting because even with less food, it felt easier than the first two days. We were both not very hungry and had more energy.

Days 4 & 5

Day four was easy and uneventful. Day five we had a HUGE amount of energy and mental clarity. I cleaned out the entire garage, which we had avoided for two years, while Seth worked all day with active pediatric patients.

Day five was a clear win. It was worth the whole experience just to get the garage cleared in one day! Crisp thinking and clear decisions, along with a lot of energy.

Two weeks later

I have to say I’m impressed with how we both feel. We each dropped about 5 pounds and held it. And other things changed:

  • The appetite suppression effects from fasting lasted and we have naturally been eating lighter. TRUE.
  • We are more aware of eating mindfully – after savoring every little piece of food for five days, and refraining from mindlessly stuffing food in our mouths while multitasking – we feel more mindful about actually sitting down and being present with each bite and enjoying our food.
  • We have both been eating less animal protein, for better or for worse.
  • Energy and mental clarity have been even-keel and fantastic, as well as physical strength. No slumps.
  • We both feel a shift in our body composition (leaner). Wow.

Is the FMD right for you?

If you’re interested in the FMD, it’s good to do it under the guidance of a practitioner if you have any medical conditions or take any medications. Someone on social media asked if fasting messes up your metabolism. If fasting is done in an evidence-based safe approach, it should actually HELP your metabolism.

There are some obvious populations that should forgo fasting, such as children, pregnant women, those with certain medical conditions, and people with “disordered eating,” – which includes binging in reaction to restriction. By the way, we had absolutely no desire to binge afterward – the appetite suppression and mindfulness towards eating continued, which could be the case with disordered eating, but it is not worth chancing it.

So, thumbs up on the FMD for:

  • Abdominal fat loss
  • Insulin resistance and metabolic syndrome (including high cholesterol and blood pressure)
  • Weight loss resistance
  • Prevention of cancer and cognitive decline
  • Change in body composition and appetite
  • Promoting regeneration and stem cell growth
  • Knocking down inflammation

Update 1 year later!

September, 2019

In the past year we created a homemade FMD program with three menus, called Fasting with Food. Check it out!


paris healing arts, doctor laura paris, dr. laura paris, dr laura paris

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  1. Hi Laura,

    I loved the personal way you wrote this. I think I would have the same reactions as you to the packaged ingredients you mentioned. I am in Pacific Grove and wrote a nutritional cookbook that is purely plant-based. It counts grams of protein and other nutrients in each meal presented, among other nutritional pages. It will be published in about a month and I thought if you were interested in doing your FMD twice annually, you might want my book as a guide to go plant-based in perhaps a more empowered, secure way more than you have been. Just wanted to reach out if there was an opening there. Thanks for your letter.

    1. Thanks for letting me know Rebecca! I wrote a homemade version of the FMD with great recipes and the exact right macros . . . but always happy to expand the recipes.

      – thanks for reading,

      1. Hi Laura,

        I look forward to doing this and taking advantage of your expertise. I’m a FM NP and medical anthropologist. I enjoy doing research and advising people with cancer, Lyme, dead ended diseases, conditions , and sub-clinical patterns.

        Health Decisions Research and Counseling
        Santa Rosa

  2. Hi Laura

    Thanks for posting your experience. I live in a country that Prolon doesn’t easily ship too (or … very expensive).

    Just wondering if you have a link anywhere to your homemade version of the diet?

  3. Looks like a program that would help me get back on track. Would like to know the cost of the program and the cost of the packaged food. Thank you for offering this support for life change. Looking forward to hearing more.

    1. Anne Marie,

      I updated some things on this article since you saw it earlier. Under the Prolon® parts, I included links to the actual product, and more details about how to do it. My homemade version beta trial as a different thing, and explained at the end of the article. Thanks for your interest!

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