On and off dieting actually the key to losing weight, new study finds

Slimmers can shed more pounds by taking a two-week break from dieting every fortnight, say scientists.

Research found it boosts dieters' chances of keeping the weight off in the long-term, the Daily Telegraph reports.

Health scientist Professor Nuala Byrne said the method combats a phenomenon known as the "famine reaction", which explains why most diets fail.

For many people it's extremely difficult to stick to a strict diet for more than a few weeks.

Prof Byrne said having breaks from strict regime actually helps and is the key to lasting success.

She said: "The intermittent group lost more weight and they kept it off for a longer period of time.

"We certainly think part of the reason this diet is working is because of the rest periods."

The study published in the International Journal for Obesity investigated the body's "famine reaction" to continued dieting and its impact on weight loss in 47 obese men.

Two groups of participants aged 30 to 50 were randomly assigned to a 16-week diet which cut calorie intake by one third, 23 of whom maintained the diet continuous.

The others did it for two weeks - then broke from for two weeks eating simply to keep their weight stable.

This cycle was repeated for 30 weeks in total to ensure 16 weeks of dieting. They not only lost more weight - but also gained less after the trial finished.

The intermittent dieters had an average weight loss of 17.6 lbs (8 kg) more - six months later.

Study leader Prof Byrne, of Tasmania University, said dieting altered a series of biological processes in the body which leads to slower weight loss - and possibly weight gain.

She explained: "When we reduce our energy (food) intake during dieting, resting metabolism decreases to a greater extent than expected; a phenomenon termed 'adaptive thermogenesis' - making weight loss harder to achieve.

"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 researchers in the past had shown as dieting continued weight loss became more difficult.

But this latest MATADOR (Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound) study looked more closely at ways to lessen the famine response and improve weight loss success.

Prof Byrne said this two-week intermittent diet proved to be a more successful means of weight loss compared with continuous dieting.

But other popular diets which included cycles of several days of fasting and feasting were not any more effective than continuous dieting.

These include the fashionable 5:2 diet which severely restricts calory-intake for two days of the week.

She said: "There is a growing body of research which has shown diets which use one to seven day periods of complete or partial fasting alternated with ad libitum food intake, are not more effective for weight loss than conventional continuous dieting.

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

"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."

Prof Byrne said: "We're interested to understand the biology a bit further to maybe refine the approach and get greater results into the future.