Poverty food is the diet of choice. Our choice

In a Havana dance hall, a tourist can find themselves caught between envy and guilt. Every woman seems to be slim and graceful, every man's stomach is toned, yet you are the one who can afford the drinks at the bar. You probably had dinner out, too – choosing from a range of food much wider than a Cuban person's ration. In Britain it is quite acceptable to compliment someone with a good figure, but it breaks the boundaries of crassness to ask anyone trapped in a permanent crisis of food supply how they stay so slim.

A recent study, however, says that, with one in four Britons obese, the Cuban Crisis Diet is the one we should look to. Scientists have found that deaths from heart disease and diabetes would fall in Britain were we to lose weight as the Cuban people did in the early 1990s, after the collapse of the Soviet Union, when there was a chronic shortage of food.

Researchers from the University of Alcala in Madrid studied health records for the population of the town of Cienfuegos, southern Cuba, between 1991 and 1995, and found that when the crisis was at its worst people were obviously slimmer – but much healthier. Not only was there a shortage of food, but fuel for transport and industry was also scarce, prompting people to walk more and take up manual labour in place of operating machinery in factories and farms. During this period, the average person in Cienfuegos lost four to five kilos in weight.

I travelled to Cuba eight years ago, long after the crisis had ended, but every person still appeared to be slender as a bamboo cane. Food remains scarce and citizens are rationed. Certain Cuban-produced foods are not permitted, such as beef, a valuable asset to the state that is offered to tourists in hotels, or exported. Slaughtering a cow illegally can result in a long jail term.

You can eat a lobster thermidor in Ernest Hemingway's favourite bar, Floridita, but the waiter who serves it may not do. The home kitchens are more preoccupied with using the 2.7kg per person monthly ration of rice, or making fritters with home-grown yams. One cringes to imagine the reaction of Cubans to the suggestion we adopt their diet when they would rather have more, and have our spare flesh, too. To live healthily in poverty, or be overfed and die younger of heart disease? It is a choice few can make.

The scientists are not commenting on the political scenario, however; rather they are highlighting the health benefits of a labourer's life in a closed country, asking the overfed and undernourished (nutritionists often refer to Westerners as the "walking wounded") to see evidence of the advantages in being famished.

This is not the first study to recommend that the British (or other Western nation) embrace the diet of the poor that is low in meat protein and high in nutritious, plant-based ingredients. The Mediterranean diet is the long-held ideal, with its unsparing use of olive oil and high consumption of greens and tomatoes. As early as 1821 the traveller Robert Pashley calculated that each inhabitant of Crete would put away 1,280g of olive oil each week.

Cretans, he said, are "very learned in olive oil". If he did not exactly note the health benefits, later visitors did. In the 1950s, the Seven Countries Study by Ancel Keys found that when the populations of Mediterranean countries adopted a Western-pattern diet (high in refined carbohydrate and saturated fat) and became less active, the risk of heart disease was increased.

It is the point about the active lifestyle that grabs the attention. Studies into the benefits of particular diets are always offering new conclusions or being rubbished by peer papers, but the one fact that is never in dispute is that the more physical work and exercise taken, the healthier the person. Every faddy diet recommends exercise; you know how it is: you can more or less eat and drink what you like as long as you run around enough. Which is why diets often don't work – eating fewer calories makes one too exhausted to go for a jog.

The Cuban Crisis Diet probably only works if you build hand-harvesting a wheat field into daily activities, or walking seven miles and back to the supermarket, carrying a child and all the shopping. Yet once again at the centre of the Cuba study's findings there is the fashionable concept that those who overindulge must reach a point of self-loathing after which simple peasant life becomes appealing.

In Britain, we have to look back several centuries to find a time when a farm labourer had a diet that, while not high in calories, was nourishing, diverse and could perhaps be called a cuisine. After the industrial revolution and mass migration into cities, the diet of the poor became very poor indeed – little more than bread and fat. But the medieval Briton had his daily pottage, a pulse- or grain-based soup into which went seasonal vegetables and herbs. Lean meat would be rationed – not just because of short supply but as part of the strict fasting laws laid down by the church – but foraged treats of snails and oysters, wild birds and berries made a menu to excite a modern gourmand.

Nowadays we have the "modern peasant", a lifestyle aspiration for well-heeled people. This does not mean living the good life and being self-sufficient, but adding rusticity to your lifestyle when you already have a full-time job. In fact, that salary is needed to afford such a lifestyle because to adopt it you need to take a few bread-making, butchery, cheese-making or brewing classes – or at least stock up on a few peasantry manuals.

Take, for example, The Modern Peasant: Adventures in City Food by Jojo Tulloh, to be published by Chatto & Windus in June. This is fairly typical fare for the aspiring neo-artisan, stuffed with stories and advice on growing your own, foraging, fermenting, preserving, DIY butchery and also recipes, many of which are high on aromatics and leaves picked from the roadside, but worthily low in calories. Having made a "culinary pilgrimage" to the wilds of Apulia, southern Italy, Tulloch heads home to London, determined to reclaim peasantry in a nice way, that is without the ragged clothes and grinding poverty, the backbreaking work, long-distance travel on foot and threat of the pox. Mostly, being a modern peasant means hanging out in organic cafés with other rich pretentious people.

Books such as this would leave real skinny peasants perplexed as to why someone would want their lifestyle. They would happily exchange a life lived hand-to-mouth for a desk job, a ready amount of cash and access to M&S ready meals. We who have lived through the industrialisation of our food supply in fast food nations know the consequences of consumerism. Through our taxes we pay approximately £4bn a year for the cost to the NHS of the obesity epidemic. We could do with a diet that is frugal, fresh and full of beans. Many of us could do with dropping a stone and I am one of them.

So why don't we all live like modern peasants? Because we do not have to. Name any fashionable diet – the Dukan, Atkins, 5:2, Cambridge, South Beach, or fads such as eating only cabbage soup or eggs. None of them works in the long term because we can stop them at any time. Why do Cuban people have lean bodies? Because what they eat is not within their control. The Crisis diet only works because the state has the power over the supply of food. That is what being a real peasant, or serf endures, and all they get is a svelte figure. Still tempted?

Rose Prince is the author of 'Kitchenella' (Fourth Estate)