Product review: ProLon fasting diet

Get the skinny on fasting with food using L-Nutra’s proprietary five-day meal programme.

Longevity.Technology scored ProLon at 23/25
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  • Complete a 5-day fast with relative ease
  • Not much variety in daily meals
  • Weight loss and proven longevity benefits of fasting
  • Headache on day one
  • Well-designed, easy to follow programme
  • Relatively expensive

LT editor in chief Phil Newman and I recently tried out ProLon – the five-day “fasting mimicking diet” from L-Nutra. The diet is based on the scientific research of the L-Nutra’s founder Dr Valter Longo. If you’d like to know more about the company and the science behind the programme, check out our recent interview with its CEO Joseph Antoun.

It should be noted that neither of us had previously attempted a five-day fast, so we couldn’t compare the experience with fast without food, but this is our story.

First impressions

We both found it a pleasure to open our sleek ProLon boxes and find everything packaged beautifully. Each day’s nutrition comes neatly packed in its own box, with a set of clear instructions for everything you need to know – very handy, especially for organisationally-challenged individuals like myself.

Seeing all your food for a week laid out like this was in some ways reassuring. For a week of fasting, there actually appears to be plenty of things to eat! There’s also plenty of flexibility around what you eat and when – as long as you stick to what’s in your box on a given day.


Every day begins with a rather tasty snack bar, which quickly became the highlight of both our days from a nourishment perspective.

Lunchtimes and dinners were essentially the same each day – a packet of dried soup along with crackers and/or olives, and sometimes a little treat at the end of the day.

You can also drink as much water and herbal tea as you like. Woo!

Day 1

I started the programme on a Monday, but Phil started on a Tuesday. We ultimately learned that the day you choose to start your fast can be important – you’ll see why later.

Phil cruised through the day fairly easily, even though he started the day with his regular swim before realising strenuous exercise is supposed to be avoided for the duration of the fast. Oops!

I, on the other hand, really struggled with a headache that set in around lunchtime and didn’t fade until after my evening meal. I suspect it may have something to do with caffeine withdrawal (no coffee during the programme), but once it passed it didn’t return again.

We both found ourselves thinking about food. A lot. The reality of how much our life revolves around eating becomes very apparent when you’re fasting.

Day 2

Neither I nor Phil awoke ravenous on the second day, which was a surprise to both of us.

This was the first day of the mysterious L-Drink – a concentrated solution that you mix with cold water (according to your weight) and drink throughout the day. Try adding one of the herbal infusion tea bags to the water to keep your taste buds happy with some flavour. You drink about a litre of diluted L-Drink over the course of the day, and its lightly sweetened flavour provides a welcome change from all the water and herbal teas.

CAUTION: Don’t make Phil’s mistake of putting boiling water in the bottle provided for your L-Drink, or you’ll end up with a work of art instead of a drinking vessel.

It’s easy to see why so many people give up on fasting – without ProLon I would definitely have given up at this point – but having the bare minimum to eat each day actually makes it possible to continue.

Day 3

The significance of getting through “hump day” was not lost on either of us, and we both powered through the day to ensure we made it past the halfway point. Energy levels remained pretty high throughout the week for both of us.


At this point I was very much missing my regular relationship with food – especially little things like stopping off for a coffee, or popping into the kitchen to whip up a sandwich when you’re feeling peckish. And, while Pro-Lon’s fasting with food approach does allow you to eat something, you do miss some of the social aspects of sitting down to eat a delicious prepared meal with family or friends.

On a recent call with renowned aging scientist Judy Campisi, she told me a joke that circulates among longevity scientists: “Caloric restriction doesn’t actually make you live longer – it just feels that way.” I could certainly relate at this point – the week was starting to feel very long indeed.

Days 4 & 5

Okay, here’s where the significance of the day you start your fast comes into effect. Having started on Monday, I had started to accept my new diet as part of my normal weekly work routine, and the final two days of my fast were completed without (much) fuss.


Phil, on the other hand, ended up facing the very real challenge of having to continue his fast into the weekend, and it ultimately proved a bridge too far. Feeling low on energy at the end of Friday (Day 4), and with a game of golf coming up on Saturday, the wheels came off and he succumbed to the temptation of a delicious bagel. Gasp!


L-Nutra advises Pro-Lon users to take it easy as you revert back to normal eating habits. We both do our best, but it’s hard to resist satisfying a craving or two!

Heading to the scales, I did drop a fairly remarkable 2kg (4.4 lbs) during the week, which was a great surprise, and the tightening effect around my lockdown-enhanced middle region was most welcome.

While neither of us can categorically say that we feel much different following our week of abstinence, we know that the science says we have probably done our healthspan some good. For me, the key thing about ProLon is that I it helped me complete a five-day fast at my first attempt. And, while Phil fell at the final hurdle, he’s confident that, had he timed things better, he’d have managed it too.

Images courtesy of ProLon and Danny Sullivan
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