Valter Longo’s Fast Mimicking Diet has been clinically proven to provide many of the same benefits of a water fast, without requiring participants to abstain from food entirely. In the post below we look at the details of the diet, including info that will help you create your own DIY fast mimicking diet.

Fast Mimicking Diet

The fast mimicking diet is designed so you get the benefits of a 5 day water fast, whilst still being able to eat something each day. Valter and his colleagues at USC (University of Southern California) have patented and designed an out of the box 5 day ‘fast mimicking diet’ (FMD). This can be purchased in the USA from for $249, and in UK from for £225. For many people, the easiest way to do the fast will be to simply purchase it and follow the instructions.

Fast Mimicking Diet – DIY Method

I think overall, buying and using the Prolon FMD diet is a great idea, for the following reasons:

  • The exact calorie and macro compositions are laid out for you, and you know that by only eating what they provide, you will 100% stay on target. Minimizing temptations to “eat a bit much” of something.
  • There’s no time/energy spent preparing foods.
  • The contents have been carefully constructed to support your micronutrient needs (for example it includes multivitamins, fortified potassium drink and omega-3 DHA oil).

However, I can think of at least 3 possible reasons why you might opt for a do-it-yourself FMD diet:

  • You live in a geographic location that Prolon do not (yet) ship to.
  • You would like to customize the foods you consume, and perhaps eat fresh or home made ingredients.
  • You are financially constricted for money, and can’t justify $249 on 5 days of food (understandable).

In those cases it’s definitely possible to create a DIY FMD diet. In order to replicate the same diet and results, you will want to start by knowing the exact calorie and macronutrient composition of the diet.

The “original” 2015 Cell Metabolism paper that described the diet quoted the composition as:

Day 11,090 calories10%56%34%
Day 2-5725 calories9%44%47%

To quote the specific section in the paper:
“The human fasting mimicking diet (FMD) program is a plant-based diet program designed to attain fasting-like effects while providing micronutrient nourishment (vitamins, minerals, etc.) and minimize the burden of fasting. It comprises proprietary vegetable-based soups, energy bars, energy drinks, chip snacks, chamomile flower tea, and a vegetable supplement formula tablet. The human FMD diet consists of a 5 day regimen: day 1 of the diet supplies $1,090 kcal (10% protein, 56% fat, 34% carbohydrate), days 2–5 are identical in formulation and provide 725 kcal (9% protein, 44% fat, 47% carbohydrate).

Since that paper was written, Valter and his team created the “off the shelf” FMD diet box (mentioned above).

Beyond calories and macros, the Prolon FMD box adds:

  • Days 2 to 5 adds a potassium fortified drink, because fasting can reduce potassium levels, so supplementing this avoids any side effects
  • Days 1 to 5 add a multivitamin daily
  • Days 1 & 5  add 200mg DHA oil each day

I’ve mentioned both of these links above already, but will mention them again in case they help you formulate your FMD diet:

  • The first is a set of tables that provide the blow by blow macros and calories for each day of the official FMD diet.
  • The second is details of the individual products in the FMD diet, with their respective nutritional information.

Posted by Alex

Hi, I’m Alex, a writer with a broad interest in nutrition, hormones, cancer prevention and gerontology (study of ageing). I write this blog to answer questions I myself have had at one stage or another. With the hope that others find it useful.


  1. Hi Alex, another comment from me. Could you please write about the refeeding part? Prof Longo says most of us seems to know what to eat. Like to have your thoughts on how you go about T+1 day FMD and how many days you consciously re-feed?
    For me, I take about 1 week to re-feed mindfully…no smoking, junk food etc, and take mostly high quality protein, vegetables, good fats and good carbs.


    1. Alex

      Hi Jason. Thanks for this message. That’s a great point about refeeding, I’ve messed up that part myself a couple times (typically by either eating too much in one go, or eating too many carbs and having a huge crash). I’ll make a note to revisit this post and go into more details on refeeding – at least a few guidelines on what NOT to do, hehe.


  2. I am a female five feet one inch who weighs 220 and has thyroid condition. I want to know if I can fast for two weeks.


    1. Alex

      Hi D Yueng. With regards to your thyroid condition and fasting, that is a question best left to your doctor. Especially if you’re looking to do an extended fast in the region of 2 weeks. I could imagine a number of possible complications when combining thyroid issues (and its medication) with long periods of not eating. So yes, as I mentioned, do seek specialized medical advice for this question.

      For anyone relatively new to fasting, I would suggest taking it in stages. Start off with a 2-3 day fast, perhaps repeat that a couple of times, then move to 5 days, and so-forth. Firstly, like anything that is practiced, it does get easier over time. And secondly, this gives you adequate experience to learn how to manage your time, energy and wellbeing as you go deeper into the fasting territory.

      Jumping straight to a 7 or 14 day fast could come with unnecessary risks.


Leave a reply

Your email address will not be published. Required fields are marked *