This article is intended solely for informational purposes. It is not meant to be taken as, and should not be construed, as medical advice. Any changes to your lifestyle or diet should be done in consultation with your doctor or health care professional.


Fasting-mimicking diets such as those discussed in this article are designed to be temporary diets, not permanent ways of eating. 

They are followed for a few days at most, after which you resume normal eating. You would starve to death if you tried eating an FMD full time. They’re a “reset” diet designed to clean debris out of your cells and senescent cells out of your body using nutrient deprivation, not a permanent way of eating.

  • Fasting Mimicking Diets (FMDs) have been around for decades. The original ketogenic diet, developed to control epilepsy, was designed to mimic some of the effects of fasting. 
  • Today’s modern FMDs were popularized by Dr. Valter Longo, who did a lot of original research related to their benefits. After several years of research, he developed his diet in conjunction with a company called Prolon. 
  • The Prolon diet is low in protein, high in carbs and moderate in fat.  It’s designed to have certain metabolic effects. You can buy the ingredients for around $220. It’s also sometimes possible to find it on sale. 
  • I have the deepest respect for Dr. Longo, his ideas, and his work. But when I tried the Prolon diet, making meals from the ingredients in the Prolon box, it didn’t work well for me. I felt hungry and distracted most of the time. The problem was that I’d been eating ketogenic diets for a while, and his diet is high in carbs and takes you of ketosis. It also has some ingredients I’m allergic to. And I’m used to eating organic food, but the Prolon diet isn’t based around organics.
  • For this reason, I started looking into alternatives.
  • One obvious one would be just to fast. This is actually easier for me. I’ve done fasts in which I drank water, coffee and tea for a few day. In some fast, I’d add cream to the coffee. In others, no cream. Water, tea and coffee fasts, with or without added cream, were easy and worked well for me.
  • The reason I decided to go back to doing fasting mimicking diets (instead of real prolonged fasting) was because of viral infections. You probably know which one I’m talking about. I’m not greatly worried about, but if I should come into contact with it, I want my immune system to have a fighting chance. Several studies have shown that while water fasting is great when you have a bacterial infection, it can. be a bad idea if we come into contact with a virus. FMDs give us lots of nutrients, strengthening our immune systems and our odds of doing well if we should get infected.

Other Fasting Mimicking Diets

  • When I realized the Prolon diet wasn’t working for me, I started looking into alternatives. You’ll find a number online.
  • All of the fasting mimicking diets that are well designed have one thing in common: they’re all low in protein – keeping it under 16 grams a day. The fat and. carbohydrates vary, but the protein is always kept to or below that number.
  • To keep your protein low, don’t eat any meat, milk, eggs or cheese during your “fasting” days. In a nutshell: avoid animal-based foods (though it’s fine to have a little cream and butter).
  • FMDs should be low in protein, and moderate in both fat and carbs. If the carbs are too high it’ll interfere with ketosis, and if the protein is too high, it’ll stop autophagy and apoptosis, and you may not get the anti-aging benefits you’re hoping for.


The ketogenic fasting mimicking diet I recommend is based on keeping protein under 16 grams a day; avoiding animal proteins; avoiding leucine and methionine; and staying under 60 grams of net carbs. 
On this version, can eat as much fat as you want, because keto diets, including keto FMDs, are about watching your basic macros, not calories. Here are some variations I’ve tried:
  • VERSION 1: Eat two avocados a day and drink some green juice made from parsley, green onions and celery. You can make your own if you have a juicer, or use a cold pressed alternative such as Suja’s “Uber Greens” juice. This is easy and painless. Be sure to add some salt to the juice or the avocado. Salted avocado right out of the fruit tastes wonderful when you’re doing an FMD. 
  • VERSION 2: Eat two avocados a day and eat a big green salad once or twice a day. Make it from low carb, low protein veggies such as iceberg lettuce, celery, carrots and cherry tomatoes. Add other ingredients if you want but make sure to stay under 15 grams of protein per day and under 60 grams of total carbs. Remember that even salad greens have some protein.  
  • VERSION 4: Eat a big plate of steamed vegetables and mushrooms once a day.  Add some avocado or some melted butter and salt.  I sometimes just buy a big bag of frozen organic broccoli or cauliflower, or Chinese-style vegetables for stir-fry, which has about 10 grams of carbs and 10 grams of protein, well under the 15 gram limit. If you need more fat, eat an avocado on the side.
  • VERSION 5: Eat two avocados per day and two glasses of water with some greens powder. (This version is popular online, but I don’t like it really or recommend it. Greens powders are high in protein, and some have been found to be high in cadmium and other toxic metals. Green salads are better, in my estimation.
  • Keeping your protein low, your carbs moderate and your fat high will allow you to get lots of autophagy and apoptosis as the days move along, and to stay in ketosis the entire time.


  • You can drink water, coffee and any kind of tea.
  • Dr. Longo doesn’t recommend coffee but he doesn’t forbid it, and I don’t see any reason not to drink it. Coffee promotes autophagy, which is what we’re aiming for when doing an FMC.
  • Earl Grey tea is a good choice because it also promotes autophagy. But any unsweetened tea is fine.
  • For electrolytes, you can take an electrolyte supplement or drink pickle juice, celery juice or sauerkraut juice, all of which have zero carbs, zero protein, and are rich in electrolytes.
  • It’s fine to salt your food normally. In fact, doing so will replenish your electrolytes. Redmond Real Salt, a sea salt not contaminated with plastic, is a good choice.
  • I would avoid drinks made with other chemical zero-calorie sweeteners such as sucralose. I’ve found small amounts of stevia and allulose to be fine. 

Questions and answers

“Why so low protein?”

  • The body needs protein to perform basic body functions. But just for the three to five days of the diet, you don’t want to create a protein deficit. This will force your body to start autophagy, cleaning debris out of your cells, breaking it down into amino acids, then using them to make its own proteins. It then moves on to cannibalizing your senescent cells, again as a source of vital amino acids. (This is how the body survives water fasts, in which no protein is coming in.)

“Shouldn’t I also restrict fat?”

  • Yes and no. In Longo’s diet, you do have to watch your calories, so your fat has to be severely limited. If you’re doing a ketogenic FMD, one approach is to go ahead and eat all the fat you want. Just make sure it’s healthy fat. Organic butter, ghee and cream from grass-fed cows, organic coconut oil, olive oil, olives, avocados, and avocado oil are ideal.
  • If your goal is weight loss, restrict your fats to about 65 grams a day.
  • If you use olive oil or avocado oil, make sure they’re real, not adulterated with polyunsaturated fatty acids such as soy, corn, safflower or canola oil, which are often rancid before you even buy them, and can be a source of reactive and inflammatory by-products when they’re metabolized.
  • Don’t deliberately overdose on fat. The point isn’t to shove as much fatty food down your throat. Just eat foods naturally rich in healthy fats like the ones above when you’re hungry.
  • If you feel woozy, try taking more electrolytes. And as Jason Fung has said, if you feel sick or feel like something’s wrong, stop the diet. Err on the side of safety.  If there’s any medical reason that you shouldn’t fast or do an FMD, don’t fast or do an FMD. “You can always fast later” once you’ve figured out what the best way forward is.

What to eat after your fast

After the three to five days are over, when you start eating adequate protein again, your body will spend about a week creating brand new stem cells — and also creating new mitochondria to replace the ones the body destroyed in the fast.

So when you go back to eating normally, eat a diet that has adequate protein (and other macronutrients).  Eating salmon, sardines, and dark meat turkey, which are rich in taurine, is essential after any fasting mimicking diet. (Taurine is one of the building blocks your body needs to make new stem cells.)

When doing a real (water) fast your body will go through autophagy and apoptosis (eating its own senescent cells). Well-designed fasting-mimicking diets should have similar benefits.

See also: “My Version of the Fasting Mimicking Diet”