Cutting the number of calories you eat by up to half for five days a month will help you live longer, scientists today revealed.
People who underwent less than a week of a heavily restricted diet showed fewer signs of ageing, diabetes, heart disease and cancer compared to a group who did not fast.
And the good effects lasted despite returning to their normal diet - however healthy that was to begin with.
Previous studies have shown that fasting for short periods - surviving on just water alone - promotes health, but is not practicable for most people, particularly the old and frail.
So the researchers created a ‘fasting mimicking diet’ - where the beneficial effects of fasting were replicated - but ensured vital vitamins and minerals were included ‘to minimise the burden of fasting’.
The medically-supervised diet cut the number of calories eaten by between 34 to 54 per cent.
On the first day, the subjects ate just 1,090 calories while the diet was restricted to 725 calories on the second to fifth days.
The subjects returned to their normal diets for the next few weeks, before repeating the five-day fast the following month, and so on.
Tests found that over a three-month period, blood glucose levels fell 10 per cent during the fasting days but remained around six per cent lower overall.
A chemical called circulating IGF1 which is associated with diseases of ageing in humans was reduced by 24 per cent.
Valter Longo, the lead researcher of the University of Southern California said: ‘Strict fasting is hard for people to stick to, and it can also be dangerous, so we developed a complex diet that triggers the same effects in the body.
‘I’ve personally tried both, and the fasting mimicking diet is a lot easier and also a lot safer.’
The diet comprised vegetable soups, energy bars, energy drinks, crisp snacks, chamomile flower tea, and a vegetable supplement formula tablet.
The diet was composed of 11 per cent to 14 per cent proteins, 42 per cent to 43 per cent carbohydrates, and 44 per cent to 46 per cent fat.
For the remaining 25 days a month, participants went back to their normal diet which they were not asked to change.
Although the study in humans was small-scale, involving 19 subjects, it mirrored research by the same University of Southern California team on mice.
The rodents underwent the diet for four days twice per month.
The researchers found that cells in the mice - including bone, muscle, liver brain and immune cells showed signs of regeneration.
The animals also lived longer, suffered fewer inflammatory diseases, cancer and showed improved learning and memory and less bone loss.
The restricted calorie diet even promoted regeneration in part of the mice’s brains - the hippocampus - involved in memory.