On Sunday 12th April, I started something that felt both structured and slightly daunting; a five-day Fasting Mimicking Diet (FMD). I did this as part of a much bigger group, alongside my husband and a good friend. This combination made it a truly unique experience which was both deeply personal, yet shared and supported.
This particular experience came about following some continuing professional development I attended around the Fasting-Mimicking Diet delivered by Layla Gordon. I was familiar with the work of Dr Valter Longo and of course the benefits of fasting but I had never tried a 5 day fast or a programme such as this.
Why?
I’ve long been interested in metabolic health, longevity, and how we can support the body at a cellular level, not just through what we eat, but when we eat.
The Fasting Mimicking Diet is designed to do exactly that. Over five days, it provides very low calories in a specific balance of nutrients to gently push the body into a fasting state but without completely removing food.
In my case, I followed the ProLon Programme, which is a fully designed, pre-prepared programme. Everything from meals, snacks, drinks are provided for you so there’s no decision-making, no cooking, and no deviation. You simply follow what’s given. This was very strange for me as I didn’t actually open the fridge until the end of Day 5 after a trip to the shops!
The science
When the body senses a lack of incoming energy, it switches gears. Instead of relying on glucose, it begins to burn fat for fuel, producing ketones and a state known as nutritional ketosis.
But beyond that, something even more powerful happens called autophagy.
Autophagy is essentially the body’s internal “clean-up” process. Damaged or old cellular components are broken down and recycled. Think of it as a biological spring clean, clearing out the clutter so cells can function more efficiently.
Another key benefit, particularly when we think about longevity, is that the Fasting Mimicking Diet is designed to help preserve lean muscle mass, even while the body is in a fasting-like state. This is incredibly important, as maintaining muscle is one of the strongest predictors of healthy ageing, metabolic resilience, and overall function as we get older.
This process has been strongly linked to longevity, reduced inflammation, and improved metabolic health. The FMD is designed to activate this without the extremes of a full fast.
The experience: real life, day by day
For me, this was as much a mental challenge as a physical one.
The structure was very clear because I was using the ProLon kit, there was no flexibility or thought about what to eat.
The first few days definitely required willpower. I felt tired at times and I naturally gravitated towards earlier nights. Hunger came in waves, especially on waking when I had a very rumbly stomach but I didn’t experience headaches, which I attribute to staying well hydrated with the herbal teas, soups, and drinks included in the programme. I had a short wave of nausea on day 3 for a few minutes but generally my body coped well with all the changes.
By day four, I could clearly see the physiological shift. My fasting glucose levels were low, and I was producing ketones therefore my body had fully entered nutritional ketosis.
Slowing down
One of the unexpected gifts of the week was the pace. I carried on with my normal exercise, but everything felt a little slower, a little more intentional. It wasn’t just a dietary reset, it also felt like a lifestyle pause.
Not everyone’s experience was the same
What I found particularly interesting was how differently people responded. My husband coped well and aside from hunger he didn’t appear challenged as long as he could have his morning black coffee he was happy. My friend, who was also doing the programme, found it a lot tougher not because of the restriction, but because of the format. She didn’t enjoy the pre-prepared meals and realised just how much joy she gets from cooking and preparing food. Without that creative and sensory experience, her mood dipped.
It was a powerful reminder: this approach isn’t for everyone.
Who it’s not for?
The Fasting Mimicking Diet is a targeted intervention, not a general recommendation. It wouldn’t be suitable for:
- Anyone pregnant or breastfeeding
- Those who are underweight
- Individuals with a history of eating disorders
- Frail adults or those over 70
- People with liver or kidney disease
- Anyone with serious medical conditions or on certain medications
This is something that should always be approached with care and professional guidance.
Coming out the other side
What surprised me most was what happened after. I didn’t feel ravenous. In fact, quite the opposite. My appetite felt calm and controlled, and I naturally gravitated towards simple, whole foods. I’ve been much more mindful since following the diet not just about what I’m eating, but how much. There’s a real awareness that my digestive system has had a rest, and it’s taken time to get things gently back online.
What I’ve taken from the experience
This wasn’t just about five days of eating differently. It was about discipline. Awareness. Curiosity. It showed me that hunger isn’t always an emergency. That the body is incredibly adaptable. And that sometimes, stepping back and taking a break is exactly what we need.
My results
From a data perspective, I found the outcomes really interesting:
- I lost a small amount of body fat
- I retained my muscle mass, which I was really pleased about
- I appeared slightly dehydrated at the end of the fast compared to my usual readings
- My metabolic age dropped by one year
For me, that balance, supporting fat loss while preserving muscleis exactly what makes this approach so compelling.
What’s next?
I’m planning to complete the recommended cycle of three FMD rounds, so I’ll be doing another in May. Then in June, I’d love to open this up more widely. If you’re curious about trying a Fasting Mimicking Diet within a supportive group setting, I might consider leading a group experience if there’s enough interest.
The other option is to follow the FMD protocol and guidance using a whole foods approach which may also be of interest to you. I am happy to provide some guidance.
If that’s something you’d like to explore, feel free to get in touch at info@thefoodteacher.co.uk.
If you want to learn more about your metabolic health sign up for The Metabolic Way and work through our group programme or book a 1:1 clinical session with The Food Teacher.
