The average British diet is making us fat and unhealthy, with nearly one in four of us in the UK diagnosed clinically obese. In contrast, people in some other countries stay slimmer and live longer, healthier lives. So what’s their secret?

In the new two-part factual series World’s Best Diet, presenter Jonathan Maitland and four celebrities — Linda Robson, Cheryl Baker, Darren Gough and Carole Malone – set out on a journey to discover why these other cultures are bucking the obesity trend and how they compare to the UK.

From raw fish in Japan to the low-carb diet in California; from vegetarian curry in India to the Mediterranean diet in Italy – each of the celebrities travel to a different nation, immersing themselves in the local cultural attitude towards healthy living and learning to cook their food. They are then challenged to maintain their regime when they return to the UK for a further five weeks.

At the same time, presenter Jonathan examines what has happened to our eating habits in the UK by reverting back to the typical post-war diet that his parents would have followed.

Which one of our contestants will lose the most weight and emerge the healthiest? And which one of the diets could turn out to be a new way of life?

In part one of the series, we meet our participants who are all desperate to shed the pounds.

Former cricketer and champion dancer Darren Gough may not look overweight at first glance, but his measurements put him in the obese category.

“I’ve suddenly retired and I need to nip it in the bud now before it gets out of hand,” he says. “I like my drink…I like my food…It’s the snacking for me and when I have a lump of cheese it’s a proper lump not just a thin slice.”

Buck’s Fizz singer Cheryl Baker has always felt fat. “I’ve always been the big girl in Bucks Fizz. There was this advert years ago “can you pinch an inch?” I can pinch loads. I can pinch yards and I hate it.” Dietician Dr Catherine Collins reveals that Cheryl would be in the healthier range if she lost 10 centimetres off her waist.

Celebrity columnist Carole Malone says she’s been on “every diet known to man” but still measures in a borderline obese. “I can’t be hurtling towards retirement eating donuts or I won’t make it.”

Birds of A Feather star Linda Robson, who is classified as obese at 13 stone 11 pounds, explains her attitude towards food. “I wake up in the morning and I’m worried about what I’m having for a lunch and then as I am having lunch I’m worried about dinner that night.”

“I feel heavy…I feel sluggish. I just want to feel a bit lighter and feel a bit healthier.

And finally presenter Jonathan Maitland, who admits to a big dessert and cake problem, is weighed and measured. Catherine gives him the bad news. “This shows that you have 50 per cent more body fat than you should have and it’s concentrated around your middle. You’re about 16 stone 2 and you’re technically obese and because you’re obese you’re at risk of heart disease and stroke and some cancers and definitely increased risk of diabetes.”

Gathered at a last supper of their favourite foods, each celebrity is handed an envelope revealing their mystery destination.

Linda likes her traditional British roast dinner so how will she cope with eating raw fish in Japan? Carole will be flying to LA to put the rigorous low carb diet to the test. Cheryl Baker, an enthusiastic carnivore, will follow a vegetarian diet from Kerala, in southern India. Darren, who hates pasta and coffee, picks Abruzzo, Italy, the birthplace of the Mediterranean diet. And Jonathan will hark back to more traditional fare from post-war Britain, cutting out the snacks and processed foods and slashing his portion sizes.

In this first episode, we follow Darren and Cheryl as they travel to Italy and India respectively.

Authentic Italian cuisine is very different from the frozen pizzas and bottled pasta sauces eaten in the UK. Italians eat 50 per cent more fresh fruit and vegetables than we do.

“Not only that but you’re using healthy oils like the monounsaturated olive oil or rape seed oil, you’ve got herbs and spices. But particularly, you are including oily fish. And that’s particularly important because the oils in oily fish are good to help stabilise heart rhythm, help protect you against heart disease,” says dietician Dr Catherine Collins.

Darren has never been to Italy before and as someone who never cooks, knows very little about ingredients. But he’s going to get some expert instruction from Aldo Zilli, one of Britain’s best-known Italian chefs who also runs a cookery school in Abruzzo. Darren gets a lesson in pasta-making and later must do the shopping on his own at a local market.

“Everything is healthy, you only have to look at their shopping list, what their weekly shop is, consists of lean meat, and fish, lots of vegetables. I’ve never seen so many vegetables on a weekly shop,” he marvels.

Darren is convinced that he will easily be able to stick to the Mediterranean diet for next five weeks when he returns to the UK.

But will Cheryl be as confident? The singer arrives in Kerala to sweltering temperatures and the supreme challenge of identifying and cooking with a completely new array of vegetables and spices.

In the UK, Cheryl’s default setting curry-wise, is chicken Tikka Masala but here food is done very differently. Eating involves a variety of tastes, small portions, a balance of carbohydrates, proteins, starches and vegetables.

Nutritionist Amanda Ursell says: “They only have 2 per cent obesity rates in Kerala which is extraordinarily low. This way of eating, because it’s low in fat and low in calories, is probably why they are so much healthier than we are in Britain. In Kerala, some of the spices like tumeric for example have been linked with their compounds actually helping to reduce the risk of cancer.”

The food is all cooked in coconut oil, which is cholesterol-free and boosts metabolism. The dishes are served on plantain leaves and as Cheryl soon finds out at a meal with Indian nutritionist Dr Smitha, eaten with the hands.

“I’m not getting the hang of it at all,” she laughs, trying to scoop up rice and curry with her fingers. “Oh, give me a fork; I’m struggling without a fork.”

On the table is a glass of hot vegetable soup – made from lentil and plenty of garlic. Dr Smitha says that it improves digestion and appetite and has the added bonus of relieving flatulence.

“You have obviously heard of my condition,” says a blushing Cheryl.

The singer explains her “condition” in a video diary entry back at the hotel. “When I arrived, I unpacked my case. This was hidden in my case,” she says holding up a picture of her family. “If you look at the message it says, ‘leave the gas in India.’ So from that you can gather that I have a bit of a problem and I do. And eating curry for a week probably isn’t going to help. But I’ll give it my best shot and see what the outcome is.”

Meanwhile back in the UK, presenter Jonathan Maitland is getting his head around how he can possibly lose weight by eating fish and chips or toad in the hole.

Top chef Ed Baines, who will be shepherding Jonny through his six-week test, explains: “The key to this diet is you must not snack because your body after about two weeks is going to get used to having three meals a day.”

Post-war, Britons limited their eating to three meals a day. Very little was processed, even less contained salt or sugar. Now it’s estimated that in the UK we eat more than half of all the crisps, crackers and nuts consumed throughout Europe each year.

Over the week, Ed gives Jonny a lesson on how to make a Lancashire hotpot using lamb and lamb kidneys and cuts Jonny’s “gluttonous” portions down to size.

Jonny also joins the butchers of Hampshire on the hunt for his rabbit dinner – a healthy white meat that has few calories than chicken…and is lower in fat and cholesterol.

“I can’t believe it. This morning, what I’m eating was running around with a fur coat and gloves on. Cor, it don’t get more British than this, does it? There’s a whole new world of cuisine that I’m discovering and the irony is, it’s under my nose.”

All three of our dieters are really enjoying their “exotic” food experiences.

And Cheryl has fallen in love with the vibrant colours and relaxed lifestyle of Kerala.

She says: “This has been quite an eye-opener India and I love their way of life, their frame of mind I think we rush about too much in the UK and here they eat slower, have time for each other, — and we should take a leaf out of their book and just sit back and enjoy our life a bit more rather than rushing and tearing around all the time.”

But perseverance is key in a six-week challenge. Can they incorporate these new diets and cultural attitudes into their everyday lives for five weeks when they return in the UK? The programme follows Cheryl, Darren and Jonathan as they try to replicate their new cooking skills for friends and family, avoid the temptation of alcohol and junk food at the various work functions, personal appearances and parties that are part of their celebrity lifestyle.

How much weight will they lose and will their new diets have any impact on their overall health?

Tuesday, 23 June 2009, 8:00PM – 9:00PM