There comes a time in life when you look in the mirror and simply don’t recognise the person staring back.
In my mind, I’m still the fit and confident undercover TV reporter who posed bare-chested on the cover of the Radio Times in 1999 and ten years later pulled on my skates to become the sequin-clad runner-up in ITV’s Dancing On Ice.
But those days feel long over and last month, shortly after Christmas, I finally saw myself as others saw me: a 58-year-old man who, despite being only 5ft 9in tall, weighed 17.5 stone and had a BMI of 36, making me medically obese.
Like many of us, I had made various unsuccessful attempts to lose weight over the years – cutting calories, reducing portion sizes, following the craze for low-carb ‘keto diets’ and so on. But in that mortifying moment, I decided it was time to try something radical.
Some people would be tempted by Ozempic or the other weight-loss jabs now so common, but somehow that felt like cheating.
I wanted to earn my new body, so I embarked on a 21-day fast during which I would eat nothing at all.
This extreme approach might seem in line with my career as an investigative journalist who has often found himself in dangerous situations – a BBC controller once commenting that I was at my best when my life was in jeopardy.
I certainly love a challenge but for all my ‘derring-do’ reputation, I knew I was in safe hands with Dr Ash Kapoor, author of a book called Autophagy: Release Our Internal Larders and my guide on what promised to be an extremely testing journey.
Slimming down: Donal Macintyre lost a total of 2st 13lb during his 23-day fast
I first met Dr Kapoor years ago, when he was my GP. Now running his own private health clinics in London and Surrey, he has become a leading authority on how fasting can improve our wellbeing and help us live longer.
The principle is simple. Our body has mechanisms which, in times of famine, are designed to dine on the reserves of fat, protein and sugar stored within our cells and around our organs – recycling this into brand-new DNA and also using it for energy.
In modern times, we never have to visit these internal larders because we are in a perpetual state of abundance, with society telling us that we must eat three times a day despite most of us being fairly sedentary.
But by fasting we survive on these larders and empty them out, a process which is known as autophagy, meaning ‘self-eating’, and effectively restores the body to factory settings.
Of course, fasting is dangerous when done without medical advice or for too long – once the body’s larder is bare, it will start to eat muscle and the patient will waste away. But a certain amount of food restriction under supervision has two huge benefits.
First, as shown in research, which won Japanese biologist Professor Yoshinori Ohsumi a Nobel Prize in 2016, it clears out the toxins that accumulate in our cells from the moment we’re born and cause the inflammation that leads to conditions ranging from heart disease and cancer to Alzheimer’s and diabetes.

Donal, a 58-year-old man who, despite being only 5ft 9in tall, weighed 17.5 stone and had a BMI of 36, making him medically obese
Donal said he wanted to earn his new body, so he embarked on a 21-day fast during which he would eat nothing at all
Almost all chronic diseases are improved by fasting and then, of course, there are the health gains brought about by weight loss. While all the medical benefits I’ve mentioned can be seen within seven to ten days, I wanted to go further and see how many pounds I could shed in one ‘quick fix’.
My regimen would be nothing but water and coffee, while every five days Dr Kapoor’s clinic will administer a solution of salt, minerals and vitamins A and B (which the body does not produce naturally) through an IV drip.
Of course, there’s nothing new about fasting. For millennia, all the great religions have espoused it — think Lent and Ramadan — and there’s something in my lapsed Irish Catholic background that savours a little deprivation. But could I make it and transform myself in just three weeks?
I was determined to succeed but, as my fasting journal reveals, I was about to put every ounce of my determination, resilience and self-control to the test…
Day one: 17st 6lb
It’s January 25, my 59th birthday. I hope this fast will be the best present I could give myself.
And I certainly haven’t woken up feeling hungry, because last night I prepared for my period of self-enforced abstinence by having a blow-out birthday meal at an Indian restaurant with family and friends. As we enjoyed the cascade of colour and flavour brought to our table, they quizzed me about my fast.
Surely I would at least be eating protein shakes? No, just black coffee and water. I hate water, whether tap, sparkling or still.
But on this first day I am distracted by having my ‘before’ photos taken for the Mail. Only a grandmother could love them but, vanity apart, there are also important medical reasons for me to lose weight.
I’m asked about the tattoo of the Chelsea FC logo on my arm – a vestige of going undercover for a year to infiltrate a notorious gang of football hooligans.
I have certainly never shied from a challenge, particularly physical ones like taking part in The Jump, Channel 4’s celebrity ski-jumping competition.
But the weight had started to creep on during the pandemic when first Covid and then a knee injury meant I couldn’t exercise like I used to.
I love a glass of wine, chocolate and biscuits – I could eat a packet of fig-rolls in one go – and within my family I have a reputation as the kitchen goat, hoovering up the leftovers and piling on the pounds.
Dr Kapoor’s pre-fast tests shocked me by revealing the consequences: a fatty liver, high blood pressure and pre-diabetes.
I am also heading for a partial knee replacement if I don’t shift what the NHS’s body mass calculator suggests is just over five stones of excess weight. The good news, he tells me, is that fasting could see me improve on all those indices ‘dramatically’.
Day two: 17st 1lb
The first eight hours are easy because I am asleep. But then, as Dr Kapoor has predicted, I quickly begin to feel strong hunger pangs and a few dips in my energy levels.
I know I will have to grind through to get the transformation I want, but unfortunately there is no chance of me retreating hermit-like to a cave and meditating as the Eastern mystics did.
I’m still a TV presenter, with a day job to do and every fast food joint I pass seems to be jumping out at me.
Donal admits that he loves a glass of wine, chocolate and biscuits and could eat a packet of fig-rolls in one go
Day four: 16st 8lb
In only four days I’ve lost almost a stone in weight, but food is constantly on my mind. Today, while recording the voice-overs for my Killer Evidence series on the CBS Reality channel, I said ‘peach’ instead of ‘punch’ and ‘confection’ instead of ‘confession’.
I’ve also taken to watching re-runs of the BBC’s Great British Menu programme. Somehow it gives me comfort as I live vicariously through the tasting and gastronomy surrounding the creation of sumptuous four-course banquets.
I dream of a gorgeous steak, triple-cooked fries and a large glass of Merlot, but I cheer myself up by noticing that my jacket is a little bit looser when I button it up.
At night, my sleep is fitful. Hunger stirs me awake (which I’d usually remedy with midnight toast), but it’s more than that. I am anxious, my body is unnerved by this empty pit in my stomach.
Day seven: 16st 3lb
Two weeks to go… any way you say it, it doesn’t get any easier. But it’s not as hard as I expected.
The empty stomach and occasional anxious moments hit me, but there have been no dizzy spells or complete drop in energy.
Today, I visit Dr Kapoor at his clinic for the first of the weekly intravenous drips of salts, minerals and vitamins.
Although the total cost of the consultations and drips necessary for long fasts like mine is about £2,100, I’ve decided that these are a sensible precaution.
Alongside the visible weight loss, the initial tests today also indicate that my glucose level has dropped from 5.9 to 4.1. It is a step in the right direction and perhaps this fast can kick me out of pre-diabetes.
Dr Kapoor reveals that I also have dramatically increased my levels of ketones – the acids produced when the liver starts breaking down body fat to use as an energy source, instead of carbohydrates from food.
Now being fuelled by fats, my brain is no longer subject to the spikes in dopamine levels associated with sugar carbohydrates, smoothing them out to produce a sense of euphoria and calm.
This explains why I’m feeling so uplifted. There is no nervous anxiety, hunger pangs or cravings. Just a quiet air of confidence that I can handle anything that comes my way.
Day 12: 15st 8lb
For the first time, I feel as if I am in another person’s body.
Dr Kapoor recommends avoiding strenuous exercise, but I’m doing light sessions on the bike at the gym and everything moves so much easier with every lost pound.
Thoughts of a large pepperoni pizza leave me salivating, but for now I know that my salvation still rests in deprivation.
Donal visits a clinic for his pre-fast test assessment and has his blood taken by a nurse
Day 14: 15st 3lb
Two weeks into my fast and I’ve never felt better. My mood and productivity are up and I feel sharp and focused.
Dr Kapoor predicted these moments of clarity during fasting and here they are. But they don’t last.
By the end of the day, my tummy feels so empty it gives me aches. I take to bed with a hot water bottle and remind myself this was never supposed to be easy and that progress has continued, with more than two stone lost in only two weeks.
Day 20: 14st 11lb
The end is now in sight and my reserves of endurance and determination are depleted. But desperate not to snatch defeat from the jaws of victory, I keep going.
I was stopped in the street by an acquaintance who thought I was ill because I had lost so much weight so quickly. I reassured her I wasn’t, while secretly glowing at the back-handed compliment. Incidentally, it has been 11 days since – how do I put this? – I last sat on the loo.
Day 21: 14st 7lb
Filming and other commitments, have often left me exhausted during these three weeks and I can see why it’s recommended to reduce your workload and exercise while you’re fasting. But on this final day of fasting I have never felt better, the epitome of vigour and vim.
So much so that I have decided to carry on. In only 21 days I have lost just under three stone – that’s the equivalent of lugging 20 bags of sugar around with you. I had intended to lose another stone over the next few months, but why not now?
Day 22: 14st 7lb
I’ve just had my worst night ever. Upset tummy and headaches. Despite my enthusiasm yesterday to keep going, it’s time to stop. But, not one to quit, I’ll give it another day.
Day 23: 14st 7lb
Hallelujah! Who’d have thought that the glorious end to a three-week fast would be a large mug of chicken broth with a hint of lemon?
It was the most delicious thing I have ever tasted.
It’s the first protein and fat I’ve had in 23 days, but Dr Kapoor has explained that it can be dangerous to race into large meals at the end of a fast. You need to reintroduce foods gently to protect your sensitive digestive system and prevent electrolyte imbalances.
Easing in supports gut bacteria, stabilises blood sugar, and extends detox benefits.
So over the next few days, I’ll be moving from broths into soft foods like cooked veggies then working up to lean proteins, fermented foods, and healthy fats for a smooth transition.
Then, in about two weeks, I might be ready for that large T-bone steak I’ve been dreaming about.
Now the challenge is to keep the weight off.
With so much progress I really can’t stand the thought of going backwards and I think I can stick to one meal a day, with some bone broth occasionally if I’m hungry.
The results have been staggering. I have changed my physique, my image and my health so much that when I attended a voice-over earlier this week, the sound recordist didn’t recognise me. Neither does the facial recognition feature that unlocks my phone!
My blood pressure is now normal. My fatty liver and pre-diabetes are gone and the need for a partial knee replacement has disappeared as my dramatic weight loss has taken the pressure off the supporting muscles and joints.
Better still, the autophagy produced by fasting has been gobbling up my double chin and jowls, rather than leaving me with the saggy skin often associated with dramatic weight loss.
I’m not advocating that a 23-day fast is for everyone, and anyone contemplating losing weight should seek medical advice first. However, now that I have succeeded, it should alleviate people’s fears of fasting for shorter periods – as few as two days – which can be hugely transformative in their own right.
Above all, in the world of cure-all jabs where Ozempic is presented as an immediate fix, it’s been a reminder for me of what makes humanity great – self-control, determination and delayed gratification.
These are the attributes that built civilisations and my small experiment reminds us that the answer to weight loss lies not in big pharma, but within all of us.