You only have to hear either of the terms “fasting mimicking diet” or “fasting with food” once to get them stuck in your head. What does that even mean?
More importantly—does it work? Cut belly fat, improve longevity, boost energy … I mean, does it really work, or does it work on health nuts who really want it to work? Is it worth the price tag?
I had to know.
I was determined to be a tough customer. I refused to fall for a placebo effect. I stared down the white shoebox that somehow contained everything I would eat for five days and told it that I really like food, that I was not excited about it, and that it would really have to prove itself.
What is Fasting Mimicking?
A fasting mimicking diet (FMD) is a prolonged (four to seven consecutive days) fasting strategy that restricts calories, while still providing specific, strategic nutrients that essentially do not register as food. It “tricks” the body into “thinking” that you’re fasting.
Not to be confused with intermittent fasting. Intermittent fasting describes a pattern of fasting and eating cycles—usually by hours in the day. There are benefits to intermittent fasting too, but prolonged fasting cues the body to do more, and that’s what the fasting mimicking diet attempts to accomplish.
ProLon is practically synonymous with the fasting mimicking diet, because it’s the first—and so far the only—packaged and clinically tested FMD program.
The ProLon Fasting Mimicking Diet is a mouthful only in name. It’s a very specific five-day diet that severely limits caloric intake in order to reap the benefits of prolonged fasting, without totally giving up food. It was created by Dr. Valter Longo, an Italian-American biogerontologist and cell biologist.
Day 1: Fasting State
The very sleek, white ProLon box revealed five smaller boxes inside. Each one was numbered, and contained my rations for one day.
I am allowed to add spices and a squeeze of lemon to anything, but that’s about it. Oh, and all the water and decaffeinated herbal tea I want.
The first day is a transition day, so there’s a little more food than days two through five. Breakfast is herbal tea and an “L-Bar,” which … is actually really good. It’s a nut-based bar with coconut, almond, and macadamia. It’s not a morning cup of coffee, but for the first morning of a fast, I have to admit, it could be a lot worse.
After a morning of virtual meetings and sales presentations, I am ready for a break, but then I remember what I’m having for lunch: soup from a packet, a few kale crackers, and a handful of olives. I’m no chef, but I do cook enough to generally turn up my nose at anything that instructs me to “just add water.”
To my surprise (and, if I’m honest, maybe to my disappointment), the soup is delicious. The kale crackers have a little bit of a peppery punch to them, which I appreciate, and I really like olives in general, so I save them for last and try my best to savor them.
Later, I get another L-Bar for a snack, with more tea. I work from home, so snacking is an affliction. I try to break up my small bar into even smaller pieces to make it last longer. Dinner is more soup, but I also get a Choco Crisp Bar for dessert, which I definitely think I earned. It doesn’t quite make up for the raging caffeine headache, but it’s something.
I put my two boys to bed and then turn in early myself. I am getting cranky.
Benefits of the ProLon FMD
The magic of the ProLon Fasting Mimicking Diet is that you reap the benefits of prolonged fasting, without actually starving and without some of the difficulties and dangers of long, water-only fasts.
There are no guarantees, of course, and every individual is different, but the benefits of prolonged fasting may include:
- Weight loss — Most of us eat more than 800 calories in a day, so, of course, drastically cutting calories will likely result in weight loss. A prolonged fast tends to specifically target belly fat.
- Enhanced cognitive performance — Clarity and focus are improved as energy levels increase around day four. A regular routine of prolonged fasting may also dramatically slow or reduce mental decline in old age.
- Healthier cells — Prolonged fasting encourages cells to clean house and repair/rejuvenate faster. Maintaining a routine of prolonged fasting can slow the signs of aging.
- Improved metabolic health — From cholesterol and blood pressure levels, to blood glucose, to inflammation, prolonged fasting helps your body regulate.
An added bonus for individuals undergoing chemotherapy, is that prolonged fasting before chemo treatments may actually improve results.
The main difficulties of fasting are compliance (it’s hard) and the possible risks involved with too severely restricting calories too often, or for too long.
The ProLon Fasting Mimicking Diet solves those problems by providing a calorie baseline to keep your heart and brain healthy while the rest of your body thinks it’s fasting. And getting a few olives and dessert bars along the way improves compliance rates.
Day 2: Fat Burning
I wake up hungry, but actually looking forward to another one of those L-Bars. I stare at my herbal tea bag floating in my mug and try to convince it to taste like a dark, fair-trade, organic Ethiopian blend cup of coffee.
It does not.
There’s only one L-Bar today, but I do get a powdered energy drink to mix into a bottle of water. ProLon recommends sipping it throughout the day, and, as I can sense I’m going to need all the supplemental energy I can get, this seems like a good idea.
Lunch is soup and olives, and I’m glad that I chose “Soup Variety 2” to swap out some squash soup instead of mushroom. It’s good. I still add some curry powder.
Tea and olives are my afternoon snack, and I am really missing that L-Bar. And Taco Bell. At least I get another dessert bar after dinner.
I go to bed early again, laundry be damned. I know it’s better than a water fast, and I try to remind myself that my cells are getting so much stronger, but I’m starting to feel physically weak.
How Does Fasting Mimicking Work? Science Time.
Here, put on this lab coat and walk with me. Let’s start with what happens during a prolonged fast.
When cells are starved for calories, they actually get stronger. It sounds crazy, but it’s true. Your body goes into a kind of survival mode. Cells stop spending energy on reproducing, and instead, spend energy on self-preservation.
The body also produces special enzymes to:
- Kill free radicals (which can damage cells).
- Prevent proteins from misfolding—a natural process that happens as people age, but which leads to degenerative diseases like Alzheimer’s or Parkinson’s.
Additionally, to make up for those missing calories, the body starts to break down its own cells (“autophagy”), which sounds scary, but it starts with the cells that are weak and damaged. It cleans house on a cellular level.
Fasting mimicking requires a low-carb, no glucose diet with a limited amount of (plant-based) protein and a higher percentage of healthy fats. This is how science “tricks” the body into triggering the health benefits of a prolonged fast, without some of the risks associated with total food deprivation.
The ProLon Fasting Mimicking Diet, specifically, makes it super easy by providing the right amount of calories and nutrients for each day in a five-day “mimic” fast.
Day 3: Ketosis (Burning Fat for Energy)
My alarm goes off and I lay in bed scrolling through food hashtags on social media until thunderous footsteps in the hall signal that my five-year-old is up and on his way to the bathroom. I have to get up.
My L-Bar is waiting and it’s still really good, but I desperately want to dunk it in coffee. My husband sees me gazing longingly at the French press and decides to drive through for coffee on his way to work.
Day three is the day that I realize there’s more going on with the food in these tiny boxes than just the nutrient science and the deliciousness. It’s texture, and I love whomever considered it.
Because the hardest part of a water fast, to me, isn’t the hunger—it’s the lack of taste and texture. Not only does ProLon’s meal kit actually taste good, the combination of L-Bars, soups, olives, and crackers provides a range of texture. Maybe I’m overthinking it, because I’m really hungry and starting to get emotional, but I just really want to hug someone for giving me something crunchy to eat.
From Calorie-Restriction to Cancer Treatment: Dr. Longo, L-Nutra, and ProLon
Dr. Valter Longo studied biochemistry at North Texas and later earned his Ph.D. in Biochemistry from UCLA. At UCLA, he worked with several doctors and scientists who were pioneering work in calorie restriction and longevity.
Dr. Longo’s work with extreme calorie restriction in yeast and bacteria, and later mice, inspired questions and ideas about calorie restriction and chemotherapy treatments.
His work soon demonstrated that organisms on severely restricted calorie diets fared better after chemotherapy treatments than their counterparts. Healthy cells responded to fasting by becoming stronger and more resilient, but cancer cells did not. Thus, chemotherapy treatments had more targeted results—killing cancer cells, while leaving healthy cells unaffected.
But it’s difficult to ask doctors to recommend prolonged fasting to patients already tired and weak from cancer and treatments. And that is how the fasting mimicking diet was born: Dr. Longo set out to design a diet that would serve the body as a prolonged fast, but still allow the patient to eat.
The company L-Nutra was established to produce the diet, so that it could be regulated, clinically tested, and then produced. ProLon is, essentially, the L-Nutra product line that delivers all the science and inspiration of a fasting mimicking diet in very convenient packages and boxes.
Days 4 and 5: Cellular Rejuvenation and Renewal
The morning of day four I wake up feeling … pretty good. I’m still hungry, of course, but it doesn’t feel so urgent.
You’re falling for it! You’re giving in!
I roll out of bed, trying to be grumpy about not getting coffee, but also noticing that it really isn’t as hard to get out of bed. I’m looking forward to that L-Bar, and I feel fairly chipper about the day.
Day five is the same. I daydream about all the donuts I’m going to eat the next day, but I enjoy my tiny, delicious meals and sipping my energy drink through meetings and project management tasks.
I power through work. I play with my kids. I catch up on laundry.
How Much Does ProLon Cost and Can’t You DIY Fasting Mimicking?
A five-day ProLon Fasting Mimicking Diet kit costs about $250. There is a small discount for ordering three at a time, or for signing up for a regular subscription. There is also a Customer Assistance Program that knocks the price all the way to $200 per box for qualified individuals.
Is it a sizeable investment? Yes it is. Is it worth it? I think it probably is.
Keep in mind it’s not a constant diet program. You’re not fasting five days every week, so you’re not paying $250 every week. For the best long-term results, Dr. Longo recommends a five day fast at least once every six months. If you stick to that schedule, it costs a little over $40 per month.
Can you DIY a fasting mimicking diet plan for less? Maybe. If you’re a very good researcher (or a nutritionist), you can probably put together your own fasting mimicking diet.
But I know I couldn’t. Dropping to 800 calories per day is hard enough, but one consolation was having my meals planned, prepared, and waiting for me. There’s an accountability built into those five small boxes and how easy they make the diet.
Also, those L-Bars are really good.
Refeeding and Beyond
Day six is for “refeeding,” and I am cautioned to take it easy. I do. With coffee.
At the end of five days I am down five pounds—so not quite as emaciated as I felt on day three, but it’s something.
I also think I noticed a change in my face. My skin wasn’t bad before, but I swear it’s brighter now. Maybe it’s subjective. Maybe it’s cellular rejuvenation.
Most importantly, I feel good, and it sticks with me for a bit. I continued to eat smaller portion sizes, and very little meat (none of it red), for weeks. My husband pointed out that I was skipping more sweets and fatty snacks than I used to as well.
A month later, my sweet tooth was making a serious comeback, which is normal and expected. What I did not expect was that I would so quickly be making plans to do it again, but I set aside $40 last month and penciled in a fast six months out.