I’m starting a five-day fast today, and, ironically, I’m making some of the best pasta I’ve ever cooked. “I think this is the best pasta you’ve ever made,” my partner says, reinforcing my thoughts as everyone else digs in happily. I can’t help but feel a bit guilty.
How did I end up here? Just a scheduling mistake. It turns out carving out an entire workweek to fast is trickier than I thought.
Fasting has gained popularity lately, and research points to its benefits, including weight loss, improved heart health, reduced inflammation, better brain function, and enhanced gut health.
What’s particularly intriguing is how some fasting methods seem to reverse aging at a biological level and may even extend our lifespan.
This occurs through a process called autophagy, which translates to “self-eating.” Essentially, when fasting, your body has the chance to clean up damaged cells and repurpose the leftovers, leading to better overall function. It’s like a cellular spring cleaning, keeping diseases at bay.
The tricky part is, autophagy usually requires extended fasting—somewhere between three to five days—which isn’t exactly a popular option. Going without food for that long, just relying on water, can be tough and should only be done under medical supervision.
Enter Italian scientist Professor Valter Longo, who wondered if it was possible to simulate fasting. After years of research, he developed the “fasting-mimicking” diet (FMD).
This five-day plan tricks your body into thinking it’s fasting, even while you’re consuming small amounts of food. The idea is that what you eat sidesteps your body’s food-detecting mechanisms, allowing autophagy to kick in.
Data from clinical trials indicated that after three or four cycles of this diet, participants—who returned to their regular eating habits the rest of the year—had, on average, reduced their biological age by 2.5 years.
Luckily for Longo, the FMD also delivers quick short-term results. You can lose weight specifically from belly fat while maintaining muscle mass, feel better overall, and even improve the look of your skin.
The downside? The cost. When not on sale, the five-day meal kit sets you back nearly £250, and you need to repeat it several times a year to really see the benefits.
I was curious to try it myself. The ProLon 5-Day Next Gen FMD pack arrived, neatly boxed for each day. Day one provides around 1,100 calories, while days two to five offer between 700 and 800 calories. Could be manageable, I thought.
Though coffee wasn’t listed on my plan, I had confirmed that I could enjoy a cup or two, as long as it was black. Naturally, I indulged in two cups.
Breakfast consisted of a nutrition bar—a sort of dense mix of nuts and seeds—alongside herbal tea and a capsule of algal oil. It wasn’t awful, but felt more like sustenance for astronauts than a satisfying meal.
Lunch included a tiny bowl of soup, a few crackers, a multivitamin, and exactly six olives. Dinner featured another small bowl of soup with another nut bar, this time with a bit of dark chocolate.
Every day, in addition to water and herbal tea, there’s a mix of vegetable glycerin and water meant to provide a smidgen of energy without breaking the fast. I found it unpalatable and skipped it.
The meals varied slightly each day. The breakfast bars stayed constant, but the “choco” bars were gone after day two. Some days there were no olives, and those precious crackers only appeared three out of five days. Thankfully, the soup flavors changed.
The challenge seemed to accumulate. Day one felt manageable, but by the end of day two I was a bit drained, irritable, and really missing the act of chewing; day five felt incredibly far away. Then, surprisingly, something changed.
On day three, I woke up feeling unexpectedly refreshed and remarkably happy. Despite the lack of food, I had an abundance of energy. I cleaned the apartment, took a walk, and even managed to shower—all by 9 a.m., which is quite unusual for me.
I worked focused and uninterrupted throughout the morning, but by lunchtime, that high faded. I was very hungry; soup didn’t make me excited, and after barely finishing it, I felt disappointed.
When I checked the next day’s menu, discovering two servings of olives and a “choco” bar, I made a decision. I would eat them today; future-me could handle any repercussions. I savored each olive like it was a gourmet treat, dragging it out as long as I could.
NNsure, I wasn’t satisfied, but all I could do was console myself with herbal tea—at least that had some flavor. By evening, my hunger subsided.
Day four was similar. I woke up on a high and buzzed through household tasks, feeling unstoppable, but that hunger returned by late morning. A trip to Tesco made me dizzy, and I thought about autophagy—how I was essentially “self-eating”—and it felt oddly tangible.
The fact that I’d come this far and had only one day left motivated me. On the night of day five, I attended my usual yoga class. My arms shook during the poses, but I was relieved to get home and go to bed, feeling cold but satisfied that I had completed the challenge.
As for results? Unsurprisingly, I lost weight—inevitable in a calorie deficit—but I was genuinely pleased with dropping 2.5 kg (the typical loss after five days) and shrinking my waist by 4 cm. What surprised me the most was how my skin looked; it had an even tone and seemed to radiate from within.
Day six arrived, and strangely, I wasn’t hungry until 1 p.m. This may seem odd, Longo noted that people often feel they could continue fasting longer. However, he advises against it—five days is optimal for benefits.
I shared my experiences with him. Everything I felt fell within the expected range; some people do experience chills during fasting, and I’d chosen a tough day for intense exercise. That sudden burst of energy I experienced matched what was happening in my body.
By then, I would have burned through my glycogen stores—our body’s energy reserves—and started tapping into “belly fat.” “When your brain starts using that,” he explained, “a sense of euphoria often arises. Mice in studies exhibit sharper responses and enhanced object recognition.”
This mental clarity, however, isn’t universal. “Some say they can suddenly master that tricky piano piece, while others struggle to concentrate and feel irritable.”
This variability contributes to the FMD’s low dropout rates. Longo mentioned initial concerns of high dropouts similar to those seen with weight-loss drugs. However, they’re observing that about 70 to 80 percent adhere to the five-day challenge.
So, did I get younger? “Yes,” declared Andrea Ghirardi, the company’s CEO, though I couldn’t measure it. Another pressing question lingers: does the weight stay off once regular eating resumes?
The answer varies. Almost a month later, I had only regained 1 kg, despite returning to my usual eating habits, which suggests I lost some fat. Longo expressed that while nourishing cells during the fast, you tend to lose fat while preserving lean mass.
Of course, critics speak up. Dr. Federica Amati, head nutritionist at Zoe, pointed out that there’s insufficient long-term outcome data. “These protocols might benefit specific groups, like those with type 2 diabetes or kidney issues.
“But I don’t think random people should try this, especially anyone underweight. I prefer focusing on sustainable dietary patterns for long-lasting health.”
Your concerns about fasting aren’t unfounded, Longo acknowledges. “I see their point. Water-only fasts can lead to malnourishment and more problems than solutions. What we offer isn’t fasting. We haven’t observed issues, but if they exist, they’re likely no worse than ongoing health problems.”
“In Italy, roughly 50 percent are overweight or obese; the UK has 60 percent, and the U.S. reaches 75 percent. There are adverse effects of poor diets. The medical community needs to step in, and I believe the FMD is a realistic way to help many return to healthier habits.”
As for me, would I do it again? Absolutely. The days following the fast felt like a brand new experience—everything tasted incredible. What will I avoid for a while? Soup.
