A Ketogenic Fasting-Mimicking Diet

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by Nils Osmar. February 6, 2022

First a precaution: Fasting-mimicking diets (FMDs) such as those discussed in this article are designed to be temporary diets, not permanent ways of eating, 

They’re “reset” diets designed to clean debris out of your cells and senescent cells out of your body using nutrient deprivation, not a permanent way of eating.

They are followed for a few days at most (usually 3-5 days) after which you resume normal eating. You would starve to death if you tried eating an FMD full time.

Typical FMDs

  • 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 FMD 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. The most popular FMD is the one promoted by Dr. Valter Longo and sold by Prolon. You buy a box of packaged food and eat it over three to five days.
  • The Prolon FMD is scientifically designed to provide the exact nutrients that Dr. Longo recommends based on his research with both animals and human volunteers.
  • I tried the Prolon FMD, but I found it unpleasant. I felt hungry and irritable when on it. (Water fasting was much easier.) I disliked that the food in it wasn’t organic. And I was allergic to some of the foods in it.
  • 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 FMDs that are well designed have one thing in common: they’re all low in protein, keeping it to under 16 grams a day. The fat and. carbohydrates vary, but the protein is always kept to or below that number.
  • FMDs are vegan. It doesn’t matter if you’re a vegan, vegetarian, omnivore, carnivore, or pescatarian in “real life”;  when doing an FMD (of any kind) you need to avoid animal products. Think of doing an FMD as going vegan, low protein, and low carb for a few days. You can go back to eating animal based foods if you want to at the end of your FMD, but not during it.

Protein, Fat and Carbs

  • Protein: Fasting Mimicking Diets of all kinds (ketogenic or not) need to keep protein under 16 grams a day.
  • Carbohydrates: Ketogenic FMDs need to keep carbs low enough to keep the person in ketosis.
  • Net carbs are calculated by adding up the total carbohydrates and subtracting the fiber. Most people eating ketogenic diets aim to get around 20-30 grams of net carbs. Depending on how much fiber  the food has, this might mean eating 30-60 grams of total carbs.
  • I’ve found that for myself, I can eat around 5o grams of total carbs, or 30 grams of net carbs when I’m doing a ketogenic FMD and still be in ketosis. But this may not be true of everyone. If you’re new to eating ketogenic, you may want to buy some ketone test strips that can be dipped in urine to gauge whether or not you’re staying in ketosis.
  • Fats: In ketogenic diets and ketogenic FMDs, you can eat as much fat as you want.

What to Eat on a Ketogenic FMD

  • 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 or celery juice. This is easy and painless (and the macros are listed on the container.) Be sure to add some salt to the juice or the avocado. Salted avocado tastes wonderful when you’re doing an FMD. 
  • Version 2: Eat one avocado and eat a big green salad once or twice a day. Make the salad from low carb, low protein veggies such as iceberg lettuce, celery, carrots, olives, 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.
  • Version 3: Eat a big (even huge) plate of steamed vegetables and mushrooms once a day.  Add some avocado or some melted butter or coconut oil or olive oil and salt.  (I know, butter isn’t vegan; it’s an exception to the “go vegan during the FMD” rule.) 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 4: Eat two avocados per day and two glasses of water with some greens powder. Make sure though that the green powder isn’t too high in protein; some will take you above 16 grams of protein a day.

What to Drink

  • I would recommend drinking water, coffee, and/or any kind of tea during a ketogenic FMD.
  • Dr. Longo doesn’t recommend coffee but he doesn’t forbid it during FMDs. I don’t see any reason to avoid it unless you have a sensitivity or allergy. Coffee promotes autophagy, which is what we’re aiming for.
  • Earl Grey tea is a good choice because it also promotes autophagy. White tea is an ideal choice for those who like it. 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 RealSalt, a sea salt not contaminated with plastic, is my top choice.
  • I would avoid drinks made with other chemical zero-calorie sweeteners such as sucralose. I’ve found small amounts of stevia, xylitol and allulose (all herbal noncaloric sweeteners) to be fine. But some people may want to avoid anything that tastes sweet.

My Experiences with FMDs and Ketogenic FMDs

  • I have the deepest respect for Dr. Longo, his ideas, and his work. But when I tried the Prolon version, as I mentioned above, I felt pretty awful. The problem was that I’d been eating a ketogenic diet for a while, and the Prolon version of the fasting mimicking diet is high in carbs and takes you of ketosis. I felt hungry and irritable while it. 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 those reasons, I started looking into alternatives. One obvious one would be just to fast. This is actually easier for me than doing a Prolon FMD. 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) during the current period of time was because of the pandemic, that ongoing nuisance in the back of our lives. Several studies have shown that while water fasting is beneficial 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.

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, fasting mimicking diets will create a dietary protein deficit (just as water fasting does). 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?”

  • In Longo’s version, you do have to watch your calories, so your fat has to be severely limited.
  • If your goal is weight loss, you might want to restrict your fats to about 65 grams a day. But I don’t count calories at all when doing a ketogenic FMD. (Ketogenic diets aren’t based around counting calories.)
  • 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.
  • I’m not saying you should deliberately overdose on fat. The point isn’t to shove as much fatty food down your throat as you can. Just eat foods naturally rich in healthy fats like avocados above when you’re hungry.
  • If you feel woozy, try taking more electrolytes. 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 FMD

  • 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.

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