'Why I'll never eat a fry-up again'

Many of life's most profound, unforgettable experiences occur in the stark, antiseptic confines of a hospital. Holding my tiny, wrinkled, newborn son in my arms; the two long weeks he spent in a special care unit, lost in a tangle of tubes; the last words my father said to me before he died. Those moments, pivotal, life-changing, are seared into my memory. Then, a fortnight ago, another: watching a man's chest being prised open and his heart lifted, bloody and beating, in a surgeon's cradling grip.

The setting for this surreal experience was London's Heart Hospital at University College London, a centre of cardiac excellence where the first heart transplant was performed in 1968. The heart I watched being manhandled belonged to Ahmed Al Haj, a 48-year-old Bangladeshi waiter, drawn inexorably to the operating table by a lifetime's dietary abuse. Although, as a Muslim, Ahmed has never smoked or drunk, his diet has been rich in ghee, the clarified butter in which many south Asian dishes are drenched – and which is composed almost entirely of saturated fat. And the Brick Lane restaurants in which Ahmed has waited, and dined, for decades are likely to have used vegetable ghee, a trans-fat dripping in artery-clogging LDL cholesterol.

I first meet Ahmed with his consultant cardiac surgeon, Shyam Kolvekar, in a neon, strip-lit corridor outside the operating theatre. Despite being sedated, Ahmed looks terrified, his eyes luminescent with fear as he awaits the triple heart bypass that will save his life. I later learn that the patient has already refused this operation once, so phobic is he of medical procedures. "Ahmed is very nervous," confirms his surgeon, a reassuring hand resting on his bare shoulder. "But I will be with you and everything will be fine," he says, gazing into those imploring eyes.

Dr Kolvekar tells Ahmed to recite a calming passage from the Koran and we leave him, eyes screwed shut, lips moving in a whispered prayer. Then we decamp to a neighbouring office, where we watch the operation on a small monitor. Dr Kolvekar talks us through the procedure in calm, matter-of-fact tones in surreal contrast to the grisly images.

"This patient is very young, of course," he says as his assistant's scalpel slices through Ahmed's chest. "Most heart bypass patients are in their seventies. I don't like operating on people younger than me – it makes me think I could be next on that slab!"

Having made the initial incision, the scalpel gives way to a cauterising instrument that cuts through deeper layers of flesh, singeing it to minimise bleeding as smoke billows upward. Next, one of the more gruesome moments, as a circular saw cuts through Ahmed's breastbone, before the ribcage is prised apart and held, gaping, with a powerful chest spreader.

For the first time we see the heart and Dr Kolvekar, sickeningly, reaches into the chest cavity before lifting it, flopping about like a fresh-caught salmon, toward the camera. "You see this?" he says, prodding it with his index finger. "The fat's so thick we can't even see the coronary artery."

It is a truly disgusting image – the healthy pink heart muscle covered in gelatinous, whitish-yellow fat. For some reason this shocks and surprises me. I knew Ahmed's arteries were dangerously furred with fatty deposits, hence his cardiac arrest a decade ago, but this suffocating, enveloping layer of blubber is really disturbing. Tearing myself away from the monitor, I peer through a window in the operating theatre's door. Seeing the scrubs-clad medical team bent over the table, instruments gleaming under the harsh yellow light, it could be a scene from ER, until I remember that the unconscious figure is the panicky man I spoke to minutes earlier.

Back to the monitor, where Dr Kolvekar is talking us through the next steps. "We remove blood vessels from the leg and a mammary artery from the chest," he says, brandishing the thick, twitching artery in his left hand. "Then we connect the veins to the coronary arteries and link them to the aorta. First, though, we have to stop the heart," he says, calm as you like.

Another unforgettable sequence: the heart is given a dose of potassium, which causes it to slow, and slow, the beat weakening until, finally, it stops. Although I know, logically, that Ahmed is hooked up to a heart-lung machine, which pumps oxygenated blood through his veins, watching his heart stop beating is just plain wrong. I feel light-headed and sick, and have to look away, taking deep breaths until the nausea subsides.

The operation now proceeds at a snail's pace as they cut and clamp Ahmed's coronary arteries, grafting the new veins with painstaking precision, the microsurgical stitches requiring remarkable delicacy and skill. Still Dr Kolvekar's smooth, mellifluous tones seep from the monitor, talking us through every step until the blood supply is restored, the heart-lung machine turned off and heart restarted, before the incisions are stitched up. "A complete success," says the doctor with understated pride. "He should be fine now."

I say my farewells, change out of the scrubs and surgical clogs, then stagger downstairs and emerge, blinking into the sunny morning. Heading home, I can't stop thinking about that fat-encrusted heart. For the rest of the day I'm in a daze – can't concentrate on anything, all normal tasks seeming trivial. And food, always a pleasure, takes on a sinister meaning. I reach for a slab of cheddar, see that heart and put it back; order a burger later, falter, and choose trout instead; salivate over bacon sandwiches the next morning, but end up munching muesli. And labels – I cannot stop reading labels. Having been a health writer for more than a decade, the fact that saturated fats should be eaten in moderation and trans-fats avoided like the plague is hardly news. I know all about omega-3 oils, free radical-destroying antioxidants, the Russian roulette played by those who smoke, drink heavily and gorge on fatty foods. But I never worried about it overly much, thinking regular exercise and common sense would suffice. I would happily sink a pint or three with friends, wolf steaks and sausages and bacon sarnies. Suddenly, I'm a health freak, scanning labels for fat content, eschewing fry-ups and the pub and running myself into a sweaty pulp every day.

The sixty-four thousand dollar question though, is why it took the horror show of watching a bypass to make me change my ways. Is that unusual? Or are the UK's soaring obesity levels evidence of a nation in dangerous denial?

"I think most people do underestimate the risk of heart disease," says Judy O'Sullivan, a cardiac nurse with the British Heart Foundation. "We know that the number of people dying from coronary heart disease [CHD] is reducing, but the number of people getting it is staying more or less the same. That's because the treatments have improved, and we have better access to testing and diagnosis, but people aren't living more healthily."

The fact that CHD remains the leading cause of death in the UK is deeply frustrating for medics like O'Sullivan, because it could so easily be different. "CHD is, by and large, a preventable disease," she says. "One of the risk factors is genetic, but you can control all the others like smoking, being inactive or overweight, having high blood pressure and blood cholesterol levels, and diabetes."

I need little convincing. Thankfully, smoking has never been one of my vices, but drinking has, so I'll keep a closer eye on those units. And fatty, greasy food now makes me feel sick, so that's history. I'm even considering banishing meat for good, despite a lifelong passion for steak.

I wonder how Ahmed is getting on so, a few days after his operation, I pay him a visit. He's propped up in bed, a nurse changing the dressings on his legs where the arteries were removed. I can't begin to imagine what his chest must look like. He seems pleased to see me, and apart from sickness and a little constipation, is remarkably well after such invasive surgery.

Is he glad he finally had the bypass? "Yes, I am," he says quietly. "My children were so worried about me – they said if I didn't have surgery I would die, so they are happy, too."

Ahmed has six kids, ranging in age from seven to 24, which is a pretty compelling reason to stay healthy. Does he intend to change his lifestyle? "I'll try," he says, somewhat unconvincingly.

We talk for a while about kids, family and how tough parenthood can be. Before I leave him to rest I ask Ahmed if he's hopeful for the future. "I think so," he says, eyes welling up. "With God's help, and Dr Kolvekar of course, I hope all will be well."

With the FSA stating that we need to reduce our consumption of saturated fat, a debate on the issue, chaired by John Humprhys on 10 September, will ask: is diet an individual's responsibility or a national concern? To have your say, tune in on online at www.satfatnav.com.

Keep your heart healthy

*SMOKING

If you smoke, the single most important thing you can do to protect your heart is to give up. Smokers are almost twice as likely to have a heart attack as people who have never smoked, because smoking damages the lining of the arteries, leading to the build up of atheroma (fatty material).

*DIET

A healthy diet helps you maintain a healthy weight; lowers your blood cholesterol level; keeps your blood pressure down; helps prevent the build-up of fatty material; and prevents blood clots from forming. Eat five portions of fruit and vegetables a day and avoid saturated fat – 88 per cent of men and 83 per cent of women in the UK consume too much. Also, avoid "bad" cholesterol-raising trans-fats wherever possible (chemically altered vegetable oils found in processed foods, sweets and biscuits).

*EXERCISE

The heart is a muscle and needs exercise to keep fit. The British Heart Foundation recommends at least 30 minutes of moderate intensity physical activity five or more times a week. This should make you breathe more heavily than normal and feel slightly warmer. It's important to choose activities you enjoy, which may be swimming, cycling, walking, gardening and even sex.

*ALCOHOL

Moderate drinking, of one or two units a day, helps protect the heart from coronary heart disease. Red wine is best, as it raises levels of "good" cholesterol and thins the blood. But excessive alcohol consumption causes high blood pressure – one of the risk factors in cardiovascular disease. And excessive drinking has a direct effect on the heart – binge drinking causes abnormal heart rhythms, while regular heavy drinking can lead to enlargement of the heart, known as dilated cardiomyopathy.

For more information on cardiovascular disease contact the British Heart Foundation on 020 7935 0185 or visit www.bhf.org.uk