Now we’ll eat like Sicilians, at least until the next fad diet comes along

At a recent breakfast with a friend, I couldn’t help but notice that she had ordered toast with jam, but no butter. I ran the evidence through my mental diet calculator. Carb plus sugar minus fat: must be either vegan or WeightWatchers. But no: “it’s actually Starch Solution”, she said, taking a giant bite before settling into an explanation of the new diet’s ingenuity in reversing received anticarb, anti-sugar, prohealthy-fat wisdom. Olive oil was out; muesli, potatoes and brown bread were in. I should try it.

I’m glad I didn’t, since this week doctors are once again hailing the wonders of the Mediterranean diet, which shuns bread and jam for olive oil, greens, nuts and fish. In fact, researchers claim, the Med diet keeps people alive better than statins, cutting the chance of an early death by more than a third.

Close observers might remember the hoopla three years ago around the very same diet, after a New England Journal of Medicine article outlining its striking cardiovascular benefits. Long before that, researchers insisted that the monounsaturated fats in olive oil could help protect against heart disease. Dr David Katz, of Yale’s Prevention Research Centre, while disgusted by the many misleading nutritional claims made by the healthy eating industry, agrees that a “diet of minimally processed foods close to nature, predominantly plants, is decisively associated with health promotion and disease prevention”.

This is a solid body of opinion, but it’s also dull. Why eat plants when another expert says you can eat chips, or lose weight much faster with Beyoncé’s maple water cleanse?

We’ve had more than a century of conflicting advice over food. Around the First World War, doctors began to recommend cutting calories. Low carb diets arrived in the 1940s from America. In the 1950s, Dr Ancel Keys’s study showed a correlation between fat and heart disease. In 1961, US guidelines hit out at saturated fat, while the 1970s witnessed the rise of both the protein-rich Atkins diet and the lower cholesterol craze.

Eggs were a classic enemy of good heath. Men were prohibited from eating steak by anxious wives. By 1987, a project was underway to remove fat totally from diets. Three decades on, it turns out olive oil actually protects the heart.My personal trajectory is telling. I have tried India Knight’s macadamia-nut embracing bestseller; WeightWatchers, which lets you eat quite a bit of frozen yogurt; and been seduced several times by the yoghurt and chicken breast-centric Dukan Diet. I admired a friend on Lighter Life, a diet of nothing but powdered drinks for three months.

Of course, lifestyle fads are a sign of wealth and relative peace. During the Second World War, people were told to “dig for victory”, and supplemented meagre rations with homegrown kale and cabbage. They didn’t have to worry about exercise since they had to walk everywhere. They may have faced existential threats, but nobody was fat.

My grandfather lived to 96 by skipping regularly for exercise, and eating what he fancied, which happened to be salami, cheese, carrots and bread that he made himself. He rarely ate fish. He never used olive oil. Still, eating like a Sicilian villager is probably sound advice. By next week, when a new fad is revealed, no doubt we’ll have forgotten about it. FOLLOW Zoe Strimpel on Twitter @zstrimpel; READ MORE at telegraph.co.uk/opinion