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Fasting for 5 Days – My Recent ProLon Journey

7th October 2025 By Catherine

If you follow me on Instagram, you’ll know I recently did a 5 day Fasting Mimicking Programme, using ProLon. I’m a huge fan of fasting, when done in the right way, at the right time of our lives. We hear so much about fasting, but it’s really important to know what you’re doing before you jump in with both feet. So here are some tips and thoughts from my 5 day fasting experience (with a special discount code at the end if you’d like to try the Prolon system). 

So what are the benefits of fasting? And what is ProLon?

When we fast, we encourage our body into a state of cellular renewal. This helps us to get rid of toxins and rubbish, have a good clean up and support cell regeneration. This is why fasting is such a great strategy for supporting our longevity.

The longer we fast, the more effective this cellular renewal process becomes.

Fasting also has been shown to support insulin sensitivity, helping to lower the risk of type 2 diabetes and cardiometabolic challenges.  It may also help balance blood lipids (eg cholesterol), protect our brains through release of Brain Derived Neurotrophic Factor (BDNF), balance inflammation and may even be helpful for supporting long-term healthy weight management.

Of course, in the busy-ness of our modern day life – it’s hard to go without food like our ancestors did. Which is where the Fasting Mimicking Programme can be really helpful – you’re putting your body into the same state as if fasting, without having to go completely without food.

I recently did a 5 day fast with my husband using the ProLon system. This was created by Dr Valter Longo, one of the pioneers of fasting research. It provides a calorie controlled, low protein system that enables you to stimulate those physiological processes of fasting, without cutting out all food. 

It comes with 5 daily boxes – which include a breakfast bar, herbal teas, 2 organic vegetable-based soups, olives and crackers. It’s based on organic, real food (which is a huge plus for me!) and super easy to follow. They also provide you with daily supplements. 

There has been a lot of research into this system of Fasting Mimicking.  For example, doing 3 cycles of Prolon over a year has been shown to reduce your biological age by up to 2.5 years!  

I also really like the fact that it’s been designed to help preserve muscle mass, supporting your metabolism and your long term health. 

So here was how I felt whilst doing my 5 day fast!

The positives:

  • My brain was super focused, calm and clear. That’s because a longer fast stimulates ketosis, providing ketones as fuel for your brain.
  • I felt light, full of energy and most “food noise” disappeared during the week.
  • Having the kit made it so much easier, especially when I also had to prepare food for my teenagers!
  • It was fab doing it with my husband – we were there for moral support, to keep each other going and keep reminding each other why we’re doing it.
  • His blood pressure dropped during the week considerably, and he really found that his carb addiction improved.
  • I slept like a baby 😊
  • A week later he is also continuing to eat a lot less food than he was before – something I’ve battled him with for many years (he is Spanish and loves his carbs!)

What was challenging?

  • I missed fresh food. But I just kept telling myself it’s 5 days.
  • I found I was a little constipated, but that is often how my bowel reacts to dietary changes.
  • There were times when my mood dropped over the week – my brain missed some carbs.
  • I found I was hyperfocused, but not so great at multi-tasking!
  • I also found my stress resilience wasn’t so great, and next time I do it I plan to have a lighter week.
  • I didn’t even attempt weight training – but kept to gentle yoga and walks.

If you’re interested in giving fasting a go, here are some final tips and guidance on whether it might be suitable for you.

  • Everyone can do an overnight fast – also known as time restrictive feeding. Aim to have at least 12 hours off food/drinks apart from water/herbal teas, every day. You can also gently extend this to 13 to 14 hours – for most people this is fine.
  • Don’t do longer fasts if you have to take medication with food in the morning, have issues with your blood sugar (eg diabetes).
    Longer fasts are not for children, anyone with eating disorders or potentially with a history of them, while pregnant or breastfeeding.
  • Fasting isn’t great if you’re super stressed or recovering from illness. When cortisol levels are already on the high side, fasting is going to push that up further.  So if you’re in a period of acute or chronic stress, it’s best to focus on 3 balanced meals daily, snacks if you need them. Nourish and restore first!
  • Avoid extended fasting if you have low thyroid. Higher cortisol can interfere with thyroid function.
  • It might be better not to fast for longer in the last week of your menstrual cycle, and potentially even during your period if you struggle with very heavy periods.
  • Children should not do an extended fast.  Also not advisable in pregnancy. 
  • If you have a pre-diagnosed medical condition or take any medication, please always check with your medical professional before completing an extended fast. 

Would you like to try the Prolon Fasting Mimicking Programme?  

If you would like to try Prolon you can use my link for 25% off HERE  CODE: CATHERINE10 

If you want to give it a go, you can order directly – and do let me know you’re planning it, I’d love to hear your feedback.

Would you like to join my new year group fast? 

I’m also planning a group fasting programme in mid-January 2026 using the Prolon system.  If you’d like to do this with group support, get in touch with me here.

Related posts:

Back to School Special: Healthy Lunch Box Ideas

3 delicious ways to cook with apples

How to get off the sugar rollercoaster...

How to control negative self-talk... it could be getting in the way of optimum health

Filed Under: Blog, Fasting, Featured, Low Energy, Men's Health, Skin, Sugar Detox, Weight loss Tagged With: 5 day fast, fasting, fasting benefits, prolon

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