Scouted selects products independently. If you purchase something from our posts, we may earn a small commission.

Like many food lovers, the word “fasting” has always intimidated me—especially since I’ve committed to exercising consistently in 2025. When I saw a food influencer post about Prolon’s “Fasting Mimicking” Nutrition program last year, I was instantly intrigued—particularly because she said she felt amazing during the entire five-day program. At the start of the new year, I was looking for a reset, but juice cleanses, and caffeine-free programs were a hard pass for me. Prolon’s program promises to deliver the benefits of fasting (we’ll get into that later) while still allowing you to eat a small amount of solids and liquids. Essentially, the low-calorie diet tricks your body into thinking it’s fasting, letting you reap the benefits without severe caloric restriction.

Dr. Valter Longo, founder of L-Nutra and creator of the Fasting Mimicking Diet (FMD), developed the nutrition program to help patients lose weight and, more importantly, reduce cholesterol, lower age-related disease risk, boost metabolic health, and promote longevity. Prolon’s program has also been clinically tested by the laboratory of Dr. Longo and Keck Hospital at the University of Southern California, which is a big deal—something many other fasting programs and cleanses can’t claim.

The super-structured program comes in one-day and five-day options. After the indulgent holiday season, I opted for the five-day reset. Proponents of the five-day diet (and the brand) say that in addition to helping you shed a few pounds, the FMD may support longevity by stimulating autophagy (inner cellular rejuvenation). Opponents argue there isn’t enough data to support these claims and suggest that sending your body into starvation mode may not be as effective for long-term health as consistently eating whole foods. As a neutral observer, I decided to test the five-day program to see what happened.

What’s Included in the 5-Day Program?

When I opened the box, I was pleasantly surprised by the organization. It contains five separate boxes for each day, each filled with your ‘meals’ and supplements. The meals come in the form of plant-based soups, bars, snacks, specific drinks, and supplements. You’re also allowed unlimited water and one cup of black coffee (minus the creamer) per day. Personally, I wouldn’t give up caffeine for anything, so this was a huge plus for me. Each day, you’re consuming around 700 to 1,000 calories, depending on the day.

The box also includes a “menu” that outlines everything you’ll eat (and are allowed to drink) for each day. Day one was the easiest since I hadn’t fasted the day before, and the program kicked off with a higher-calorie day. Days three and five were definitely the hardest—and based on other reviews, I wasn’t alone—because you’re only getting about 700 calories, and you don’t get your end-of-day “treat,” the Choco Crisp L-Bar.

What’s On the Menu?

Each day starts with a nut-forward bar, which is pretty satisfying and helps keep you full. Lunch is usually a soup of some sort, and in the afternoon, on three of the days, you get either kale and almond crackers or a pack of olives. Dinner is another soup, and on days one and two, you get a small “dessert.” You’re also given a glycerin liquid to mix with water, which “provides the body with an alternate energy source to use instead of lean body mass during days 2-5 of the fast,” as well as several herbal tea bags. Again, the unlimited water and tea, plus one cup of black coffee, were my saving grace.

What Does the Food Taste Like?

It’s not the best food I’ve ever had, but I didn’t expect it to be. I was surprised by how good some of the soups, crackers, and olives were. I expected to feel famished and repulsed by the soups' flavor (or lack thereof). While I definitely wouldn’t choose the Carrot Ginger soup again, I really enjoyed the Green Pea and Chives and Lentil Curry soups and would eat them even if I wasn’t on the FMD diet. The kale and almond crackers and olive packs were also delicious.

I’m already hunting for alternatives on Amazon and Costco so I can enjoy them every day. I was also impressed by the creamy consistency of the soups. I had imagined they’d be chalky (like some powdered greens supplements), but they weren’t at all.

Can You Exercise While on Prolon?

In theory, yes. In fact, the brand suggests you maintain your normal lifestyle as much as possible while on the program. However, I kept my workouts low-impact (i.e., walking) and skipped my usual heated Pilates fusion classes and weight training. These classes are heated to 105°F and combine bursts of cardio and HIIT. I was worried about feeling faint, and they significantly increased my appetite. With brisk walks on an incline for three of the five days, I felt OK (I skipped days three and five because I was more tired and lightheaded).

My Results

By day six, I had lost five pounds. While most of this was likely water weight, I haven’t regained it yet. I attribute this to the transition diet (days six and seven), which is recommended after the program. The brand suggests slowly introducing easy-to-digest foods like beans, grains, and lean protein in the two days following completion. Despite the significant caloric reduction, I didn’t feel as exhausted and malnourished as I’d anticipated. The third and fifth days were challenging, but that was mostly due to temptation from others around me who weren’t doing the cleanse. If you follow a lot of food influencers or enjoy reading restaurant reviews, I recommend taking a break from this during the program. Trust me, watching TikToks of Mukbangs and food reviews will test your willpower. I learned this the hard way.

Another concern I had was how the reduced calories would impact my sleep. I typically don’t sleep well when I don’t eat a good dinner, and I tend to eat later than most. I can’t go to bed hungry and still function the next day, especially with only one cup of coffee. Fortunately, like many others, my sleep was OK. The fifth night was rough, and my Oura Ring called me out for my lack of “readiness,” but I figured one night of subpar sleep was worth the other benefits. Plus, I didn’t feel sluggish or zombified the next day, which I attribute to the FMD benefits.

TL;DR:

This was much more manageable than I expected, and I will definitely do another five-day program before summer.

It’s important to note that Prolon is not for everyone, especially athletes, those with eating disorders, or individuals with certain health conditions. It’s always recommended to consult your physician or healthcare provider before starting a new diet or lifestyle shift.

MORE FROM SCOUTED: