DID you know there are people called ‘breath-air-ians’ who believe we can exist on air alone?

“That’s madness, a lot of people have died doing that,” says Dr Michael Mosley. He’s the man behind the 5:2 Diet, but don’t get him started on fad diets...

Dr Mosley is in Bradford next week with his show, Trust Fast Health. Working in TV for over 30 years, as a science presenter and producer, he’s seen a “huge revolution” in medicine and personal health, and diet. “A lot of things we were told about diet turned out not to be true,” he says. “On my first day at medical school the Dean said, ‘You’ll study here for six years, within 10 years most of what you’ve learned will be out of date’. The medical world’s understanding of diet and fitness is changing. In my show I’ll reveal where it’s all going and what the big surprises will be. One myth is that a fast diet won’t work - but all the evidence now is that rapid weight loss is effective. The only thing that matters is that it’s a good diet. There are 20,000 different diets out there, most are terrible.”

Such as? “The most popular new weight-loss diet is juicing, but that’s dangerous. It doesn’t give you any protein,” he says. “If we don’t get protein, within 24 hours our body will start to cannibalise itself. Some crazier low-protein diets have led to people dying of heart attacks. The blood-type diet, which says your blood type predicts what kind of food you can eat, is nonsense.”

On his first UK tour, the doctor is exploding health myths and offering insights into the human body. “It’s a very interactive show. We don’t want lots of questions about ingrowing toenails, but it’ll be great hearing what people find funny and curious,” he says. “It’s fantastic when people say you’ve helped turn their lives around. I’ve met people who were going to have their leg amputated because of diabetes who’ve managed to avoid that by following my advice. There’s great power in taking control of your own life.”

Dr Mosley talks about his unconventional journey, from swallowing tape worm to uncovering revolutionary ways to lose weight and reduce stress. His new book, The Fast 800, looks at how to combine rapid weight loss and intermittent fasting for long-term health.

He started as an investment banker but, realising it wasn’t the career for him, went on to study medicine. Qualifying as a doctor, he started producing science and history documentaries for the BBC, first behind the camera then a presenter of such shows as Blood and Guts and Inside The Human Body. His new show, ITV's The Junk Food Experiment, sees famous faces such as singer/presenter Peter Andre, Olympian Tessa Sanderson, MP Nadine Dorries and Shaun Wallace of The Chase live on junk food for a month.

One positive advance in our health is, says the doc, that we’re cutting back on medication we take. “Once we were just happy to pop pills. Now we’re aware that’s not necessarily making us any better,” he says. “We’re living longer, but in ill health. There’s a greater awareness that food plays a critical role in whether we’ll develop conditions such as heart disease, diabetes and cancer.”

Dr Mosley had global success with his 5:2 Diet. What led him to invent it? “Six years ago I discovered I had Type 2 diabetes. My dad died from that. He did a lot of crazy diets, none worked. That led me to find out about intermittent fasting,” he says. “I made a documentary, Eat, Fast & Live Longer, about my search to reverse diabetes, which led to me finding out about the 5:2 Diet. People didn’t know you could diet by doing intermittent fasting, but the fact that I managed to lose 20 pounds and reverse diabetes by following the diet was compelling. As soon as the book came out, it took off. It’s been a New York Times best-seller, been published in 42 countries and sold three million copies. It continues to resonate.”

Inspired by past research of “young doctors doing horrible experiments on themselves”, he pitched the idea of a TV programme to BBC controllers for 10 years. “They all said no, until a controller called Janice Hadlow finally said, ‘Why don’t you do it? You’re a doctor’. We found a doctor keen to get healthy people infected with a tapeworm to see if he could find any bio-markers.I volunteered. Tapeworms are good at controlling the immune system, I get bad hay fever, so was interested to see whether a tapeworm could improve that. I won’t reveal the outcome - you’ll have to see the show - but it was surprising and worthwhile.

His wife, Claire, a GP works with him on the books. They met at medical school. “We bounce ideas off each other. I run things past her, like: ‘What do you think, darling, about me swallowing a tapeworm cyst?’ or ‘I’m keen to make a film about torture and I want to be water-boarded’. She’ll reply: ‘That’s not a good idea - you’re over 60!’”

* Dr Michael Mosley is at St George’s Hall on Friday, March 8. Call (01274) 432000.