The CSIRO has, perhaps surprisingly, launched a new diet that includes intermittent fasting three days a week.

It might sound counterintuitive, as fasting diets have traditionally been considered about as ineffective and nutritionally inadequate as the much-maligned Atkins or cabbage soup diets. But research now shows that they can be just as effective as standard, calorie-controlled diets.

The weekly ‘Flexi’ program, which is available in pharmacies and offers a recipe book along with online resources, comprises three fasting or ‘control’ days where dieters consume 40 per cent of their energy requirements, three kilojoule-controlled ‘classic’ days and one free ‘flexi’ day where there are no dietary restrictions.

Meal-replacement shakes, soups and bars are consumed on control and classic days in addition to whole, food-based meals and snacks.

The program is based on comprehensive research by the CSIRO which saw participants following a fasting diet in the 16-week trial lose an average of 11 kilograms each while also achieving improvements in cholesterol, insulin, glucose and blood pressure levels.

CSIRO research dietitian Dr Jane Bowen says the diet offers an alternative to traditional, calorie-controlled diets because it focuses on routine and energy intake over a full week.

“This is something a bit different that will suit some people because the routine of the meal replacement can really help people know what they need to do, and a lot of people respond to that level of structure and prescription,” she says.

“They’re able to vary their energy intake, so some days they eat less, which enables them to eat more on other days. We know that life gets in the way and often people will fall off the wagon [of a typical diet] if they have a wedding or a party.”

The diet allows for one cheat day a week. Photo: Getty

Associate Professor Amanda Salis, from the University of Sydney, says a growing body of research shows  intermittent fasting stacks up against more typical approaches to weight loss.

“Whether you’re doing a diet that involves continuously restricting the amount of kilojoules you consume from one day to the next or whether you do an intermittent fasting diet, the research is showing that at the end of three, six and now even 12 months that your weight loss will be similar,” she says.

And even though meal-replacement products may sound like they belong with the fad diets of old, the experts agree they are an essential component of the Flexi program.

“The fasting days are much more likely to be nutritionally incomplete – it’s pretty hard to have a fasting day that meets nutrition requirements without using meal replacements,” says dietitian Melanie McGrice, a spokesperson for the Dietitians Association of Australia.

Crucially, however, the control group in the CSIRO’s research consumed an energy-restricted diet every day of the week and also lost 11 kilos, so nutrition research scientist Dr Tim Crowe says it’s important not to discount traditional approaches to weight loss.

“The results look impressive, but the control group who were on a more traditional calorie-controlled diet for seven days a week, consisting of two meal replacements and one healthy meal of vegetables and protein, also had the same amount of weight loss,” he says.

“Fasting diets do work for weight loss, but not everyone has the same success. And when you compare them to more traditional diets, they don’t offer an extra advantage for long-term weight loss.”