I’m Doing Pro-Lon’s Fasting Mimicking 5-Day Fast — And Here’s What They Don’t Tell You

Taryn Hillin
8 min readFeb 25, 2021


Let’s fast, I said. It’ll be fun, I said. We’ll challenge ourselves and improve our health.

Well let me tell you, I’m at the end of Day 3 (of 5) and I’m about to eat my cat.

A little backstory, I’ve been wanting to try Prolon’s Fasting Mimicking Diet for a while now. When I was in cancer treatment I found all of Dr. Valter Longo’s research on intermittent fasting and was sold (My tumor has the KRAS gene mutation so I was especially interested). I did twenty-hour fasts, two times per week while going through chemo. The five-day fasting-mimicking diet (FMD) allegedly gives you the same benefits of a water fast but allows you to eat a small amount of food (thus avoiding the negative side-effects of fasting). I won’t get into the benefits, you can Google them. I’m literally too tired to write them out — did I mention I’m at the end of Day 3?

(Update: they include weight and body fat loss, lower blood insulin, increased energy, lower blood cholesterol, the potential for anti-cancer effects (tumor suppression), lower IGF-1 factors, and most importantly ketosis and autophagy, aka cellular cleanup.)

Anyway, post-cancer-treatment it was risky for me to do FMD because I went down to 113 pounds. But now that I’ve gained some weight (I’m starting around 125 lbs) I roped my husband into doing Pro-Lon’s “fast” with me — after all, I’m on a journey to not only beat this rare cancer but live a long healthy life after months of chemotherapy and radiation. It’s no small order.

So let’s talk about how it’s going …

Gwyneth Paltrow did it, lots of wellness influencers online have done it and I’ve got to say — I’m annoyed they don’t talk about how difficult it is.

Allegedly, 95% of people complete this fast, so apparently, my willpower is pretty weak. I decided to write this blog in real-time because I’m pretty sure once I complete the five days I’ll look back and see this time as rainbows and butterflies. “It was great, you’ll love it, it’s a reset for your body” I’ll say, forgetting how awful it really is.

Honestly, looking back at chemo I’m like “eh it’s not that bad”. But would I do it again? Hell no. My brain is clearly blocking out the terrible-ness of it. In order to avoid that problem here, I’m writing in my most hangry state.

Truthfully, I thought this would be easier. I usually eat around 1300 to 1500 calories per day anyway, so, in my mind, I thought cutting back wouldn’t be too hard. Indeed, I thought my husband (who sneaks donuts sometimes) would be the one struggling. But it’s me! Here’s how it’s going so far.

Day One

This day was fine. It’s around 1100 calories, so for me, it was not difficult. For my husband, this was the day he almost gave up. After work, he snuck four olives because he was so hungry (every calorie counts here folks). But he pushed through. Me, I was fine. The nut bars, soups, olives, and crackers were enough. I was hungry, but it was fine.

Day Two

The calories drop from 1100 to around 750 on this day. You would think that wouldn’t be too bad, but there really is something about those extra 350 calories that you really miss. I also just miss eating in general, as in the act of preparing and eating food. Since getting cancer I didn’t realize how much of my day is dedicated to thinking about food, preparing food, and eating that food. Whether it’s fruit/veggies smoothies, a fully cooked meal, a tossed salad — I look forward to it. Now, I miss cutting the vegetables, smelling the lemons, popping garlic stuffed olives while I roast purple sweet potatoes. I miss all of it!!!!!!

On this day I got QUITE hungry at night, so much so I went to bed around 9:30 pm. I knew day three would be hard since my calories were getting cut once again. My husband meanwhile was breezing through, not a care in the world. Men, right?

Day 3

I wake up HUNGRY. I want coffee (you’re allowed 8 ounces). I savor every bite of my nut-bar (my mother even comments that I’m eating it extremely slowly). I’m nervous because I have a three-hour infusion of vitamin C and I’m always ravenous afterward. You’re supposed to stop supplements, but I can’t stop my cancer treatment stuff (IVC works great for KRAS), so here we are. By the time I get home, around 4 pm, I’m starving. I told my husband I feel like a lion on the hunt — my senses are heightened in a way that I might kill someone and eat them. He seems to be giddy and fine. He’s apparently experiencing that fasting energy some people get. I AM NOT.

The day drags on. I eat my butternut squash soup (which is really a cup of water with a 100-calorie-freeze-dried soup-powder inside) slowly. I split my kale crackers in half. Half for now and the other half for dinner. Normally the afternoon snack is olives and after dinner, there’s this rice bar thingy. But today no such luck. No olives, no rice bar. Just two soups, each one cup. I’ve decided having my kale crackers for dinner is a must, even though it means a light lunch.

I go for a walk. I feel weak. That’s the other thing, you can’t really work out on this fast because you’ll use up too many calories. Another thing I do all day — yoga, walks, stretching — all gone from my daily routine.

I contemplate quitting all day. Seriously, I’m only writing this blog post right now, so I don’t quit. I’m holding myself accountable through public shame. I sneak one olive at dinner. No joke, I ate that one olive for five minutes. I just held the flesh in my mouth and sucked on it.

Now my cat is driving me insane as I type and I might eat her.

Days four and five will be rough. I know it. I’m trying to remind myself of all the good — but all I feel right now is bad. My willpower is weak. I suffered so much with cancer I just want to enjoy every day I have. I don’t want to wish myself to Saturday. I keep Googling “Can you end Prolon early and still get all the benefits?” but apparently people don’t write about this. I want it to end.

One thing I will say is I have often thought about other people at this time who are also hungry right now — not because they’re fasting but because they don’t know where their next meal is coming from. This hunger thing is awful. I am lucky. I can end at any time and when I make it past Day Five, I will celebrate with delicious food. Many people don’t get that luxury and walking in those shoes, even partially, has been eye-opening. You can’t fake how hunger feels. Either you know it or you don’t and it does things to your mind.

On that note, I’m off to bed at 9:37 pm because, really, what else is there to do without food. LOL.

UPDATE With Day 4, 5, and post-Fast data!

Day 4

Day four was not as difficult as Day 3 (I believe there are a few more calories on this day), but I was still hungry and my energy was at an all-time low. Each day of the fast I walked between one and two miles, but it was a drag.

Day 5

“Please let this end now”, is all I can think. The real bummer of this fast has actually been my mood. I do not feel “reset, rejuvenated, or refreshed”. I feel cranky, irritable, and crazy. I’m really starting to contemplate “What is the meaning of life without food?” I’m not seeing it. I know all the benefits this fast can offer — so I do not regret doing it — but it has been rough and I’m not sure I’ll do it again for a while. My diet is restrictive enough already, so five days of even more restrictions have been a real nightmare. I broke down around midnight (so technically Saturday, Day 6) and ate some food. It was too much to bear.


I started this fast at ~125 pounds, I ended at 118 pounds. The company says the average weight loss is around ~5 pounds and my ProLon coach (because I’m trying not to shed too many pounds) assured me I might not even lose that — but I lost more than that. I lost nearly eight pounds. I’m hoping in the next week I will put back on at least five pounds with a regular diet. I did have some weird theory that because I already do calorie restriction and don’t eat sugar that perhaps my body was in a closer “state of fast” before starting and the company does have rules about BMIs 18 or lower NOT being allowed to do the fast (my BMI is 19). So, definitely be careful if you’re already underweight.

If you want to lose weight this is a great kickstart, my husband lost six pounds as well. Again, men are more likely to lose weight at higher numbers and people starting with more weight are more likely to see numbers lost in the range of 6 to 12.

My scale data from Day 1 to Day 6. (The fast ends on Day 5.)

I’ve read many blog posts on Pro-Lon about people wanting to eat better and no longer craving sugar. The opposite happened for me. I don’t eat sugar (as in no added sugar or even dried fruit or coconut) and I don’t really ever crave it. But all I wanted to do last night was shove cakes and cookies in my mouth or order a pizza. I didn’t! But I wanted to. I knew my stomach would kill me after five days of no food.

Overall, I feel like shit today — so there’s that. I’m doing my best to focus on the positive. I know there are science-backed benefits to this, especially in terms of cancer and disease prevention. I’m definitely not knocking the program. I would advise having a partner to do it with (otherwise you might kill someone), not having too much work that week, and not having too little either (I was quite bored and cranky).

If you don’t need all the cellular clean-up and just want to lose weight I have three tips:

  1. Cut sugar
  2. Cut alcohol
  3. Fast for 20 hours, 2x per week (i.e. Monday and Thursday).

That’s all folks!


For those who don’t know, I was diagnosed with Stage 3C Small Cell Neuroendocrine cancer in October 2019. There are less than 200 cases per year. There is no research, funding, or clinical trials for this cancer. If you would like to learn more please visit https://necervix.com/facts/.



Taryn Hillin

Writer, journalist, media strategist. Sony TV Diverse Writers '21; Universal Writers '22; Formerly of HuffPost, Fusion, TMZ, and VP Strategy ENTITY. Yale grad.