Intermittent fasting has become the diet trend of the decade.

It promises to hack biology without the drudgery of counting calories or cutting carbs: simply change when you eat, not necessarily what you eat. Tech moguls swear by it, Hollywood stars insist it keeps them trim. Britain's former prime minister Rishi Sunak once spoke of starting his week with a 36-hour fast.

So far the science has seemed supportive. Research suggests that extending the overnight fast may improve metabolism, aid cellular repair and perhaps even prolong life. Nutritionists, however, have long warned that skipping meals is no magic bullet - and may be risky for those with underlying conditions.

Intermittent fasting compresses eating into a short daily window, often eight hours, leaving a 16-hour gap without food. Other time-restricted diets, like the 5:2 plan, limit calories on certain days rather than hours.

Now, the first large-scale study of its kind raises a more serious red flag. Researchers, analysing data from more than 19,000 adults, found that those who confined their eating to less than eight hours a day faced a 135% higher risk of dying from cardiovascular disease - death due to heart and blood vessel diseases - than people who ate over 12-14 hours.