My night shift had been a busy one. As a trainee cardiologist at Harefield Hospital, I’d treated a steady stream of patients - among them, a man who was suffering from advanced heart disease and required emergency surgery.

As I toured the wards early the next morning to check on him, the breakfast trolley was doing the rounds. What was on the menu? Sugary cereals, white toast, jam and marmalade galore.

As I began my speech on the benefits of a healthy diet, my patient looked at me steadily before saying: ‘How do you expect me to change my ways when the place I’ve come to for healing is serving the same c**p that got me here in the first place?’

Where had we gone so wrong? Yes, we’d ditched the old dietary demons of bacon sandwiches and fatty fry-ups - but for what?

This was six years ago - but I still remember it clearly. Because it was at this moment I had something of an epiphany.

He was right. The hospital trolley laden with processed foods was emblematic of how badly we were eating as a nation.

And my night of inserting emergency stents (a thin tube to hold open an artery) showed all too clearly the impact poor diets were having on our health and happiness.

Yet I couldn’t answer his all-too pertinent question.

So where had we gone so wrong? Yes, we’d ditched the old dietary demons of bacon sandwiches and fatty fry-ups — but for what?

Troubled, I went home and embarked on a project of research that was to absorb me for years. And what I discovered was revolutionary.

Today, yes, I work for the NHS. But I find myself in the peculiar position of opposing the dietary advice we doctors are taught and expected to preach to our patients: that we should cut back on fat to lose weight and keep our hearts healthy, and fill up on carbohydrates instead.

So even if we don’t succumb to a slice of cake with our afternoon cuppa, a significant proportion of us are consuming up to 40 teaspoons of sugar every day without even realising it

This mantra is blindly preached and repeated by health professionals despite numerous studies now confirming that some fats are essential to our survival, and that eating more fat, not less, is actually very good for you.

It’s this misguided advice that led to my poor patient recovering from a serious heart operation being served processed, sugar-laden junk by the very people who were supposed to help him get better.

And I believe it is this misguided advice that has partly contributed to processed carbs and sugar becoming an endemic part of the British diet.

Don’t think that just because you aren’t one for a biscuit at elevenses or a bar of Dairy Milk for an afternoon pick-me-up you’re immune from all this.

Anyone who eats anything out of a packet - from sliced bread to pasta sauce - is at risk. Food today is packed with hidden sugars, so much so that sugar has become a component of almost 80 per cent of all processed foods.

Add to this the fact that simple carbs, such as white flour, potatoes and rice, are metabolised into sugar by the body, and you can see we’re sitting on a dietary time bomb.

We’re ordered to drink skimmed milk, to cut the crispy skin off our chicken and to use processed margarines, not butter - even though these natural fats are exactly the type our body needs to function efficiently

So even if we don’t succumb to a slice of cake with our afternoon cuppa, a significant proportion of us are consuming up to 40 teaspoons of sugar every day without even realising it.

Meanwhile, fat has been completely demonised. We’re ordered to drink skimmed milk, to cut the crispy skin off our chicken and to use processed margarines, not butter — even though these natural fats are exactly the type our body needs to function efficiently.

I’m convinced this high-sugar, low-fat diet has become a leading cause of death in the Western world - and not just because sugar is a leading contributor to the worldwide obesity epidemic, it’s an independent risk factor for so many chronic ailments ranging from type 2 diabetes to heart disease.

For as well as triggering an overload of insulin, which can have a catastrophic metabolic impact on the body, sugar also appears to make cholesterol more inflammatory — and therefore even more damaging to the heart’s arteries.

Not only this, but a daily diet of processed foods leaves our body on a roller coaster, bouncing from sugar spike to sugar spike, our mood veering wildly along with it.

No wonder so many of us feel lethargic and jaded. My own research, which took into account numerous studies from all over the world, has turned up compelling scientific evidence for cutting sugar in favour of boosting fat intake.

Yet, worryingly, this research is consistently dismissed or ignored by the bulk of the medical establishment.

In this regard, we Brits are falling far behind our neighbours. Even the Americans, so often criticised for being sluggish when it comes to dietary health and with even more alarming obesity statistics than ours, are ahead of us on the sugar front.

In 2009, the American Heart Association published a paper outlining the dangers of sugar and recommending a maximum daily limit — for heart health if nothing else — of no more than nine teaspoons for men and six for women.

I assumed there would be recommended upper limits in the UK, too, but when I checked, all I could find was a ‘guideline daily amount’ of 22 teaspoons. I was appalled.

So what did I do in the face of all this bad advice? Just what I recommend you to do — I ignored it, and transformed my eating habits with my own personal food revolution, one that ran completely counter to all my medical training.

NEW WAY OF HEALTHY EATING IN A NUTSHELL The diet I follow is fundamentally low in carbohydrates and high in healthy fats. As such it is diametrically opposed to conventional dietary advice across the world, but it is gaining interest and gathering medical backing. And the Mail has made it so simple to follow with exclusive extracts from the new book Sugar Free by Karen Thomson, and superb four-page pullouts — featuring delicious recipes — all next week. Switching to a low carb, healthy fat (LCHF) diet will mean eating fewer carbohydrates and a higher portion of fat than you’re used to. It means cutting out sugar and starches (such as whole grains, cereals, bread, pasta, rice and potatoes) and putting the emphasis on healthy fats, while maintaining an adequate intake of protein (fish, meat, eggs and dairy products). It is about eating whole foods and cooking from scratch whenever possible, focusing on food quality and the nutrient boost from REAL foods as opposed to the processed versions that have crept into the Atkins world. With a typically carbohydrate-based diet, carbs and sugars are converted to blood sugar which your body burns for energy. Any excess sugar is converted to fat (under instruction from the hormone insulin) and helpfully stored out of the way. However, if you restrict your carbohydrates to 50g per day or less, your body can no longer get the energy it needs from sugars so it has to bring in other fuels. This is where fat comes in. The body can get the energy it needs from stored fat and the fat content within food. An LCHF diet relieves the body from the tyranny of sugar addiction — the peaks and troughs of blood glucose and insulin. This is great news for your health, but also for your figure. Without sugar, you’ll see improvements in your skin, mood and concentration, a reduction in cravings and — finally — a proper sense of whether you are truly hungry, or whether it’s just sugar talking. This makes LCHF a naturally easy way to lose weight, because your body has to turn to fat — taking it from your waist, bottom and thighs. Visit doctoraseem.com Advertisement

I cut back on carbs and radically upped my intake of fats. In short, I ate what made me feel fabulous.

This was no strict diet or punishing regime. I can still sit down to a glass of red wine and a big, juicy steak topped with butter. And guess what? I’ve never felt better. And my health has never been so tip-top, either.

I’ve recommended all my heart patients follow this type of eating plan. And you can, too, with exclusive, mouthwatering recipe guides from health and diet expert Karen Thomson, who will show you how to eat to feel fabulous all next week in the Mail.

So how have my patients fared? After all, by encouraging them to increase their intake of fats — including saturated fats such as butter, cheese and yoghurt — I’ve effectively been promoting the so-called ‘poison’ they were told damaged their hearts in the first place.

Happily, I can tell you their lives have been transformed — and that’s no exaggeration.

My patients leave my office with two simple instructions: cut out processed carbohydrates and sugar, and eat more fat. I tell them not to follow the Government-recommended low-fat diet.

I also tell them to avoid all food labelled ‘low fat’ or ‘proven to lower cholesterol’ and instead just eat real, whole foods.

To their amazement, the health impact can be extremely swift. One man in his 50s lost 3 st in six months just by cutting out sugar.

So how have my patients fared? After all, by encouraging them to increase their intake of fats - including saturated fats such as butter, cheese and yoghurt - I’ve effectively been promoting the so-called ‘poison’ they were told damaged their hearts in the first place

He couldn’t believe this simple step could work when conventional dietary advice had failed for most of his life. But I could.

He’s not alone. I received an email recently from a man with type 2 diabetes who had read a newspaper story in which I had extolled the virtues of eating more fat.

He said that to his family’s ‘horror’ he had started eating butter again while cutting down on carbohydrates. He was writing to thank me because his cholesterol levels were the best they had been in years.

A female patient in her 40s was referred to me with dangerously high blood pressure. After two months of cutting out sugar and refined carbohydrates, her blood pressure normalised and she came off medication.

My own life has been transformed, too. I’d always had a sweet tooth. I used to start my day with sweetened cereal and fruit juice, drink a bottle of Lucozade after my gym workout, grab a panini and a chocolate bar for lunch and then sit down to a huge bowl of pasta or curry with rice and naan bread in the evening.

Don’t think that just because you aren’t one for a biscuit at elevenses or a bar of Dairy Milk for an afternoon pick-me-up you’re immune from all this

Incredibly, given the amount of food I was eating, I was always hungry. I’d often polish off a large slice of chocolate cake to quell the hunger pangs before going to bed.

I started my diet revolution by simply cutting out sugar and refined carbohydrates — white bread, pastries, pasta and white rice — and being more generous with the olive oil, nuts and seeds.

Then, 18 months ago, I stopped eating bread altogether (even wholemeal) and reduced my intake of starchy vegetables such as potatoes and pulses.

Cauliflower rice or courgetti spaghetti are my options instead these days. And my overall food intake more closely resembles that of the Greek/Mediterranean diet, which has a rich, scientific evidence base for good health. I’ve radically upped my intake of saturated fats because I’m sure they will protect my heart, not attack it. After all, the most natural and nutritious foods available — meat, fish, eggs, dairy, nuts, seeds, olives and avocados — all contain saturated fat.

And so today, I may have a two or three-egg omelette packed with vegetables for breakfast or lunch, along with a handful of nuts.

I’ll reinforce my coffee with either a knob of butter or a spoonful of coconut oil to keep me feeling fuller for longer.

I pour extra virgin olive oil lavishly over my salads and vegetables. Indeed, I aim to consume at least four tablespoons of olive oil every day because studies show it is great for heart health. And, yes, I enjoy a glass of red wine, too.

While people think fruit juices and smoothies are healthy, they really are little better than liquid sugar. So instead, I have berries alongside my egg-based breakfast and — once a day — an apple for pudding after dinner.

All in all, I couldn’t feel better. In the old days, I had a pot-belly which stubbornly resisted my attempts to slim despite an intense daily exercise regime.

Now, at 38, I’m a stone lighter than I was five years ago.

The belly fat has disappeared, even though I now exercise far less than I used to. Why? Well, when you eat a carbohydrate-based diet, carbs and sugars are converted to blood sugar.

Any excess sugar that’s not used for energy is converted to fat. However, if you restrict your carbohydrates, your body has to use other fuel — and that fuel comes from your body’s fat stores.

Aside from these benefits, life is much simpler when you’re not distracted by the cravings and gnawing hunger eating sugar and processed carbohydrates generates. Indeed, carbohydrates induce addictive eating behaviours.

I have co-produced a documentary, The Big Fat Fix, which explains how cutting sugar and eating healthy fats can boost our longevity

When your diet is predominantly based on refined carbohydrates, the body’s ability to recognise it’s full is hindered because sugar interferes with appetite signals.

So if the dietary advice I was given at medical school was right, today I should be a walking time bomb with soaring cholesterol levels and advancing heart disease.

But I have regular check-ups and have never been healthier. I’m convinced my diet is protecting me against heart disease, premature ageing, cancer and dementia.

New research that supports my food revolution is being published all the time. Just this week, significant research by Tufts University near Boston, in the U.S., proved that even a whole tablespoon of butter a day would not raise the risk of heart disease — yet more proof that the demonisation of butter for decades has been a mistake.

While people think fruit juices and smoothies are healthy, they really are little better than liquid sugar

Provided you cut back on sugar and refined carbohydrates, butter can be very much part of a healthy diet. I probably get through a whole block of butter every four days. Unsurprisingly, I have met plenty of resistance along the way.

And despite all the evidence, the ‘healthy eating’ guidelines in this country remain unchanged, something that I believe is nothing short of scandalous.

So why aren’t all doctors recommending this plan to patients?

The wheels of bureaucracy move very slowly. And so much established dietary advice incorporates the commercial interest of large food companies. You can’t escape the fact that low-fat processed food is big business.

What can we expect when in 2012 the London Olympic Games, the biggest celebration of fitness and health in this country for decades, was sponsored by Coca-Cola and McDonald’s?

And as long as influential organisations such as the British Nutrition Foundation have memberships that reads like the Who’s Who of the sugar industry — Coca-Cola, Kellogg’s, McDonald’s, Nestle and Pepsi among them — and the British Dietetic Association can promote fruit juice as part of a balanced diet, I fear it will still be some time before advice is changed.

But change it must. I have co-produced a documentary, The Big Fat Fix, which explains how cutting sugar and eating healthy fats can boost our longevity. It will be released in the next few weeks. We’ll see if that does the trick.