So you want to live to 100, do you? Well, after visiting some of the world's longevity hotspots, Jamie Oliver reckons he can show you how. The chef has identified 14 "hero" foods from those regions - ranging from walnuts and sweet potatoes to seaweed and chillies - that he says should help you make it to your centenary and which have helped him to shed two stone.
Oliver, though, isn't the first man to have made this journey. An adventurer and documentary-maker from Minnesota beat him to it and even published a book about it earlier this year. It was called The Blue Zones Solution: Eating and Living Like the World's Healthiest People.
Dan Buettner spent a decade studying long-lived communities in so-called blue zones to find the lifestyle and diet traits common to the people there. People in these zones significantly outlive the rest of us, enjoying lower rates of heart disease, diabetes and dementia and boasting proportionately the highest number of centenarians.
Studies have shown, Buettner says, that genes dictate only 20pc of longevity, with lifestyle and environment accounting for the rest, so he wanted to discover the nub of their longevity.
The zones pinpointed were Ikaria in Greece, Okinawa in Japan, the Barbagia region of Sardinia, Loma Linda in California (which contains the highest concentration of Seventh Day Adventists in the US) and Nicoya in Costa Rica. So now, post-research, do we find Buettner telling us to become teetotal, go on a strict diet, eschew caffeine, hit the gym or start training for marathons? No we do not.
That's where the western world, wedded to its detoxes, new year diets and personal trainers, has been going wrong. Self-discipline, he says, is a muscle that tires, and such regimes have failure rates of more than 90pc. No, the people he spoke to who successfully lived to 100 don't have super self-discipline, organised exercise routines or purist diets. The key to their longevity seems to be that they live in cultures that make all the right choices without them noticing.
"None of these people try to live to be 100," says Buettner. "They are products of their environment."
So what is the key to long life? Those living in blue zones usually do lots of walking, grow their own vegetables and often go to bed late and sleep in late. However, if he had to sum it up in a single word, it would be "beans".
From studying the blue zones, Buettner believes that beans are "the world's greatest longevity foods" and that eating beans - of every variety, including fava, black, soy and lentil - is fundamental to healthy living and the "cornerstone of every longevity diet". The blue-zone people are "eating a cup of beans a day on average".
Which brings us to the other striking feature of these people's diets: they eat very little meat. In most of the blue zones meat is consumed on average just five times a month - about once a week - and in a serving about the size of a deck of cards; 95pc of their diet comes from a plant or plant product.
This contrasts with millions in the obesity-ridden West who eat meat every single day, sometimes more than once. Buettner closely analysed blue-zone diets and found that in Ikaria, for example, among older people, meat accounts for just 5pc of their diet, with greens, vegetables, beans and fruit making up the vast majority.
It isn't that they don't like meat or object to it, but simply that it is treated more like a "condiment" or celebratory item than a regular staple food.
Buettner is the son of a former dairy farmer who grew up as a "midwestern meatloaf and pork chop eater" in a part of America where there are "six pigs for every human", yet he no longer eats meat and describes himself as pescatarian.
He believes that one day "our meat-eating habits are going to be looked at in the same way as we look at our smoking habits in the 1970s.
"There will be die-hards that do it but no one will be ignoring the fact that it is seriously endangering our health and lowering our life expectancy."
Why are beans so special, though? We know they are high in fibre, vitamins and micronutrients but they also remove the need for animal protein, so are better for the gut.
"When you eat a lot of meat, the gut bacteria, the flora, of your gut changes to digest it," says Buettner. "So a certain type of bacteria thrives when you eat a lot of meat; that bacteria causes inflammation, which is at the root of every age-related disease."
When you eat beans, however, you switch to another type of flora (it is during this changeover that flatulence occurs, but he says it only lasts a couple of weeks), which lowers inflammation and is "highly correlative with lower obesity".
Buettner, whose first book on the subject, The Blue Zones, became a bestseller, has also identified nine traits; what he calls "the power 9". They include, cheeringly, drinking wine (people in all blue zones "drink wine moderately and regularly, even some Adventists"); natural movement, such as walking to work or doing housework rather than pumping iron; eating mostly plant-based food (what he calls the plant slant) and stopping eating when your stomach is 80pc full (blue zoners eat their smallest meal in the late afternoon or early evening and don't eat any more for the rest of the day).
Blue zoners also drink strong coffee. A minority of them (mainly men) even smoke or have smoked in the past. "The bad news is: smoking kills. The good news is that if you quit you can still live a long life."
A UK report last week found that poor diet is now a more important factor than smoking for causing fatal illness, but Buettner doesn't rule out any of the things other health programmes might advise you to avoid. When it comes to beverages, the blue-zone way is to have coffee at breakfast, tea in the afternoon, wine at 5pm and water all day, and never to have fizzy drinks, including diet ones.
Buettner now runs the Blue Zones Project, encouraging US communities to adopt better eating habits to improve the nation's health - the largest preventive health care project in America.
He sympathises with those suffering ill health and obesity. "If you are overweight and suffering from a chronic disease it's probably not your fault," he says, adding that in 1970s America a third as many people were overweight. "It's not that they [in the 70s] had better diet programmes or education; nor did they have more discipline or were better people than we are. It's that our environment has changed. You can't walk through an airport or get cough medicine without running into a gauntlet of sugar sweets, candy bars and crisps.
"In America if there are more than six junk food emporiums within half a kilometre of your house you are 35pc more likely to be obese than if there are fewer than three. It has to start at the food policy level. Subsidies have to shift away from sugar and meat and candy and dairy and towards healthy food."
Buettner, 55, is a former endurance cyclist, and once cycled 12,000 miles through Africa, but these days he favours less-intensive exercise, such as walking and yoga. Does he feel expectations to live to 100 himself?
"I feel no pressure," he says. "I want to enjoy life. I try to uncouple me from the research: don't necessarily do what I do, do what I tell you the longest-lived people have done. I don't pretend to be an icon of longevity."
He knows that people will occasionally want to eat and drink exactly what they fancy. The key is to gradually reshape your environment (in ways such as not keeping certain foods in your house), so that if the temptation isn't there, eventually neither will be the habit. He says the single most surprising thing he found was that nobody who has lived a long time ever set out to. "Longevity is not something to pursue," he says. "It is something that ensues." As one centenarian said to him when asked the community's secret: "We forget to die."
'The Blue Zones Solution: Eating and Living Like the World's Healthiest People' by Dan Buettner, is published by National Geographic Books
Vegetables: Fennel, kombu (seaweed), wakame (seaweed), potatoes, shiitake mushrooms, squash, sweet potatoes, wild greens, yams.
Fruits: Avocados, bananas, bitter melons, lemons, papayas, plantains, tomatoes, pejivalles (peach palms).
Beans: Black-eye, lentils, chickpeas, fava beans, black beans, other cooked beans.
Grains: Barley, whole-grain bread, brown rice, maize, oatmeal.
Nuts and seeds: Almonds, all other nuts.
Lean protein: Salmon, soy milk, tofu.
Dairy: Feta, pecorino.
Added oils: Olive oil.
Drinks: Coffee, tea, red wine, water.
Sweetener and seasonings: Garlic, honey, mediterranean herbs, milk thistle, turmeric.
Eat at least three of these blue-zone foods daily: beans, greens (spinach, chards, kale, fennel tops, beet tops), sweet potatoes, nuts, olive oil, oats, barley, fresh fruit, green or herbal tea, turmeric.
Food principles from the blue zones
1. Plant slant: See that 95pc of your food comes from a plant or plant product.
2. Retreat from meat: Eat it no more than twice a week.
3. Fish is fine: Eat up to 3oz daily.
4. Diminish dairy: Cow's milk doesn't figure significantly in any of the blue zone diets.
5. Occasional egg: No more than three a week.
6. Daily dose of beans: At least half a cup of cooked beans daily.
7. Slash sugar: No more than seven added teaspoons a day.
8. Snack on nuts: Two handfuls a day.
9. Sour on bread: Replace common bread with sourdough or 100pc wholewheat bread.
10. Go wholly whole: Eat foods that are recognisable for what they are, eg, made of a single ingredient, be that raw, ground, cooked or fermented.
Jamie Oliver's 14 'hero' foods
• Goat's milk
• Sweet potato
• Wild greens and herbs
• Black beans
• Fresh fruit
• Wild rice