Fasting Pt. IV: The Fasting Mimicking Diet

In the 4th and final part of this series on fasting, I’m going to dig into the Fasting Mimicking Diet (FMD). The brainchild of Dr. Valter Longo, Head of the USC Longevity Institute here in Los Angeles, California. For this write-up, I read Dr. Longo’s book, The Longevity Diet, to get the gist of the FMD and for 5 days, experimented with a modified version of the diet for myself. I’ll start by saying, I highly recommend the book. It’s a great read filled with lots of practical information and a bunch of healthy, nutrient-dense recipes that are low in calories but still extremely tasty and filling. I did a modified version of the FMD. The full version of the FMD is available in a subscription box from Dr. Longo’s Company, ProLon. It likely does the job better than a modified version, but I can’t imagine the recipes laid out in the downloadables are much different.

What is the Fasting Mimicking Diet?

It’s pretty much exactly what it sounds like. Some kind of sorcery where you can eat food, yet have your body work and act like it’s in a fasting state. What makes the FMD method so attractive is that it curbs the discomfort and dangers of a water-only fast. You’ll eat decent amounts of extremely nutrient-dense food which reportedly helps you:
  • Feel full
  • Lose weight (sometimes very quickly)
  • Maintain muscle mass
  • Get adequate amounts of vitamins and minerals
  • Lessen hunger pangs/cramping
  • Lessen dizziness, headaches, rapid heartbeat and other water fasting symptoms
All this while still receiving the rejuvenating benefits of a regular 5-day fast.

Day 1 of the FMD was very manageable. Not the usual amount of calories, but not an uncomfortable deficit either.

Day 1 of the FMD was very manageable. Not the usual amount of calories, but not an uncomfortable deficit either.

This diet was created because the rejuvenating effects of fasting on the body are significant. Those with dire health conditions are the ones who could benefit most from these effects. Yet, those same people already in significant discomfort are often not willing to stop eating food for prolonged periods as this would only increase their current levels of discomfort.

Imagine trying to not eat for a day, after literally every day of your life, eating 2 or more meals a day. It’d be an extremely jarring test of both physical and mental willpower. Fasting used to be something that was environmentally-imposed, and in a world where food is so readily available, self-imposed depravation is beyond difficult, even for those practicing modest calorie restricting diets.

The FMD is a way to trick your body into fasting mode by adding and restricting different types of calories. Largely centered around the balance between ratios of Fats, Carbohydrates and Protein along with reducing the overall amount of calories eaten.

Fasting Mimicking Diet Breakdown

The FMD is usually done in 5-day cycles as putting the body into a calorie-restricted state for too long could end up doing more harm than good. Your body responds to low and mid-level stress by acclimating and getting stronger, anticipating the next round of stress. It’s the foundation of aerobic and anaerobic exercise and why you get stronger and healthier each time you hit the gym. But working any part of the body day-after-day without rest days, will eventually cause fatigue, injury and ruin the results you were hoping to get in the first place. That goes double for fasting. When you fast, your body is clearing out and recycling damaged cells, but in order to replenish what has been destroyed, it needs calories, specifically proteins to be used as fuel for creating new healthy cells. Fasting essentially puts your body on standby for new nutrients, and withholding those nutrients for too long will eventually cause damage.

Missed the mark this day as I had one too many carbs, but interesting to see what’s recommended in a normal diet vs. FMD.

Missed the mark this day as I had one too many carbs, but interesting to see what’s recommended in a normal diet vs. FMD.

Calorie Restriction is an essential part of the FMD and is carefully managed when practiced correctly. Studies on humans, animals and yeast have shown the effects of cutting calorie intake by half (or more) over a period of 3-5 days, on alternating weeks, had positive effects on markers of longevity across all groups. The calorie counts for a cycle of FMD are fairly simple:

  • Around 1,100 or 5-7 calories/1lb of body weight on the first day

  • Around 800 or 3-5 calories/1lb of body through the next 4 days

  • After the cycle has ended, you return to a normal (healthy) diet to feed the body the proper nutrients needed to restore what was lost or cleared during the FMD cycle

The balance of Fats, Protein and Carbs are key to achieving the proper results throughout a cycle of FMD. This is due to the necessity of entering a ketogenic state while practicing the FMD. Too many carbs can trigger the body to revert to the standard glucose-burning mode. The same can happen when too much protein is eaten. The body only needs a certain amount of protein daily for normal healing/building functions to happen. Anything protein ingested beyond your normal threshold and not being used will be processed by the liver, turned to glucose (signaling the body to burn glucose) and then stored as fat. Macros for the FMD should look like:

  • 5-10% carbohydrates – ideally 20g of carbs/sugar or less

  • 10-15% proteins – from healthy sources like grass-fed, wild-caught, cage-free and organic meats

  • 70-80% healthy fats

Supplementing with the proper vitamins and minerals. Most important of those being electrolytes like sodium and magnesium that may be lost during fasting. Water consumption tends to rise during fasts while at the same time the body isn’t receiving the amounts of nutrients it’s used to. This could cause flushing of vitamins and minerals needed to support essential functions of the body.

My Experience

Before day 1 of the FMD vs. after day 5 of the FMD. I lost weight very quickly but didn’t seem to lose muscle mass. Aerobic activity was a bit strained for a day or two after but rebounded pretty quickly after resuming a normal diet.

Before day 1 of the FMD vs. after day 5 of the FMD. I lost weight very quickly but didn’t seem to lose muscle mass. Aerobic activity was a bit strained for a day or two after but rebounded pretty quickly after resuming a normal diet.

I ran a personal experiment with this diet for the full 5-day cycle, using recipes laid out in the PDF available for download when I purchased the audio version of The Longevity Diet. It has multiple weeks-worth of recipes in case you don’t like certain recipes available during any particular cycle. The experience was overall great, especially in comparison to water fasts, which I’ve done three times in my life. I hated each time more than the last.

One thing I will say, is it gets expensive and annoying. I traveled to probably 6 or 7 different stores to get everything I needed for the week. There are a good amount of niche items like barley and spelt that aren’t usually found in your normal grocery aisle. Not to mention specialty items are often quite a bit more expensive. I probably spent more on ingredients than I would have if I just bought the pre-packaged FMD box from ProLon, but I think there’s higher overall value in actually purchasing your own items. For around the same price, you have plenty of healthy leftover ingredients to eat for the next week or two.

I was hungry, but not “fasting” hungry, which was not at all surprising given the recipes. Some (not all) of the meals I ate throughout the week looked like regular-sized portions, which made me highly skeptical at first. In terms of amount, it looked like a normal, sometimes even large plate of food, and I constantly told myself that I shouldn’t be eating this much. This was probably causing some sort of trickery in my brain as well. But once I entered the ingredients into the MyFitnessPal app, I saw the difference. It may have looked like a lot, but the ingredients are carefully curated to be low calorie and nutrient-dense. And the meals are filling! I got hungry at regular intervals, just as often as I would during a normal diet.

I lost weight…fast. To be honest, I wanted to see if I could go for an extra day because I was just generally impressed and curious about how the hell this was even working. But, I’m naturally a fairly slim guy and I was starting to get a little too small. The FMD is incredibly effective at directing your body to mobilize fat, b/c it literally just melted away. I started out around 182lbs and by the morning of the 5th day I was down to 174 and some change, the lowest I’ve been in my adult life.

The meals are DELICIOUS and incredibly simple. I maybe used 3-4 different herbs in rotation for any meal that had to be cooked. Breakfasts were extremely simple, satisfying and I was able to drink coffee or tea every morning. Dinner was max 6-7 ingredients with a few herbs and salt if needed. Olive oil was an absolute staple in most of the cooked meals, which was fine by me b/c it’s delicious and works with so many different dishes already. There are even snacks worked into the mix every day. Not your typical sugary kind, but still enough to semi-quench your snack and dessert craving. My favorite snack is macadamia nuts with dried blueberries anyway and there were a few snacks that were pretty close.

All-in-all it was a pleasant experience and a great tactic to use not only for general health, but for an accelerate weight loss solution. Unfortunately I didn’t have tests run to check the internal effects of the FMD, but I plan on doing so down the line. I’m interested to see the effects a few cycles would have on longevity markers and risk factors for diseases.

I’d recommend this diet to those in good health, but there are some serious conditions like kidney and liver problems that could be complicated by water fasts, the fasting mimicking diet or other forms of calorie restriction. Good health or not, any new diets should always be performed under the supervision of your medical professional.

Happy Holidays!