But you can lose about the same amount of weight while on a standard diet of reducing your daily calorie intake in a much less restricted way.

The mean weight loss after six months for those on the standard calorie-reduced diet was 5.5kg (12lbs), while those on the 5:2 diet lost 5.3kg (11.7lbs), according to researchers from Austin Health and the University of Melbourne.

The randomised study involved 24 obese male war veterans aged 55-75 years, who had five counselling sessions with a dietitian over the six-month study, one of the researchers, Margie Conley, told the Dietitians Association of Australia’s national conference in Melbourne.

One group went on the 5:2 diet – which originated in the UK – restricting them to 2,500kJs, or 600 calories, on two non-consecutive days a week while they ate normally on the other five days.

The others, who on average had been consuming around 10,080kJs (2,400 calories) a day, went on a diet cutting their daily intake by 2,500kJs (600 calories).

Men in both groups lost body fat and girth, with the standard calorie-reduced diet group reducing their percentage body fat by an average 2.3% and their waistline by 6.4cm.

The figures for those on the 5:2 group were 1.3% and 8cm.

Eating just 2,500kJ (600 calories) over a day might mean having two poached eggs and some spinach for breakfast, 60g to 80g grilled chicken with a side salad of cucumber and tomato for lunch, and a small piece of fish with vegetables for dinner.

“Compliance rates were similar for the two groups, but the 5:2 diet group reported being hungrier, especially early on in the study,” Conley said.

“Interestingly, weight loss slowed at the three-month mark for both groups, which was when the dietitian follow-up tapered out, showing support may be the key element in continuing success.”

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