Continuous dieting slows metabolism and can actually hempen weight loss, say experts.

Australian researchers found people who took a two weeks on, two weeks off approach to weight loss shed more kilos.

They also kept it off for longer than those who dieted continuously, according to the study published in the International Journal of Obesity.

Professor Nuala Byrne, Head of the University of Tasmania's School of Health Sciences, says dieting alters a series of biological processes in the body that can make weight loss harder to achieve.

"When we reduce our energy intake during dieting, resting metabolism decreases to a greater extent than expected; a phenomenon termed 'adaptive thermogenesis'," explained Professor Byrne.

This is the body's reaction to perceived famine and can explain why weight loss becomes more difficult the longer a person stays on a diet, says Prof Byrne.

"This 'famine reaction', a survival mechanism which helped humans to survive as a species when food supply was inconsistent in millennia past, is now contributing to our growing waistlines when the food supply is readily available," Prof Byrne said.

To investigate ways to lessen this famine response, researchers conducted the MATADOR trial funded by the National Health and Medical Research Council (NHMRC) of Australia.

During the study, two groups of participants took part in a 16-week diet which cut calorie intake by one third.

One group maintained the diet continuously for 16 weeks while the other maintained the diet for two weeks, then broke from the diet for two weeks eating simply to keep their weight stable, and repeated this cycle for 30 weeks in total to ensure 16 weeks of dieting.

Those in the intermittent diet group not only lost more weight, but also gained less weight after the trial finished.

The intermittent diet group maintained an average weight loss of eight kilograms more than than the continuous diet group, six months after the end of the diet.

"It seems that the 'breaks' from dieting we have used in this study may be critical to the success of this approach," said Prof Byrne.

"While further investigations are needed around this intermittent dieting approach, findings from this study provide preliminary support for the model as a superior alternative to continuous dieting for weight loss."

According to eating behaviour Per Sodersten - Professor of Behavioural Neuroendocrinology at the Karolinska Institutet in Sweden - dieting is a "mistake".

He went as far as blaming the obesity epidemic on fad dieting.

"We always tell audiences that dieting is the cause of all eating problems, overweight as well as underweight," he said.