Dieters should forget the advice about losing weight slowly rather than shedding the kilos rapidly, according to Victorian researchers.

Dieters should ignore advice that shedding the kilos slowly is better than rapid weight loss, a new study suggests.

Weight-loss guidelines recommend gradual weight loss for dieters, reflecting a widely-held opinion that dropping kilos slowly leads to less weight regain.

But a Victorian study found losing weight quickly is the best way to achieve dieting goals and is not likely to result in greater weight regain than the slow approach, according to a paper published on Wednesday in The Lancet Diabetes & Endocrinology.

Experts say the study highlights the need for health practitioners to change their advice for the management of obesity.

"Our results show that achieving a weight loss target of 12.5 per cent is more likely, and drop-out is lower, if losing weight is done quickly," said researcher Katrina Purcell from the University of Melbourne.

Researchers divided 200 obese men and women into two groups - half undertook a 12-week rapid weight loss program, while the others were on a gradual 36-week plan.

The 12-week dieters ate a low calorie, low carbohydrate diet and the 36-week group ate a balanced diet based on current dietary recommendations.

All participants aimed for a loss of 12.5 per cent or more of their body weight and those who succeeded were then placed on a three-year maintenance diet.

"We debunked the myth that the quicker you lose weight the quicker you put it on," said lead researcher Professor Joseph Proietto of the University of Melbourne.

"It makes no difference to weight regain.

"But what we found in the process was that with our rapid diet the success rate for reaching the target weight loss amount was higher - we weren't expecting that."

Only half of those on the 36-week plan achieved their target, while 81 per cent of those who did the 12-week diet achieved their weight loss goal.

However, at the end of the trial, about 71 per cent of the participants in both groups had regained the weight they had lost.

The initial successes may be due to the fact that losing weight quickly may motivate participants to stick to the diet, Prof Proietto said.

But more importantly, the limited carbohydrate intake of the fast-track group may have promoted greater satiety, and less food intake by inducing the production of hunger suppressants called ketones.

"The people that lost weight rapidly had higher levels of ketones," he said.

When people eat less carbohydrate, their bodies turn to fat for energy and more ketones are generated, he said.

Professor Susan Jebb, of University of Oxford in the UK said the study shows that the common claim that more rapid initial weight loss is associated with more rapid regain is false.

"This is important because it will enable professionals to recommend a broader range of treatment options so that people may be more likely to find the one that is best suited to their lifestyle," she said.

But UK-based dietitian Gaynor Bussell warned that on rapid weight loss diets where hunger is suppressed due to ketone production that ketones can make the blood pH too acidic, which can cause kidney damage.

"Most studies have shown slow weight loss to be better for a number of reasons; one of these is that rapid weight loss can mean that more muscle mass is lost than if the weight loss is gradual; thus lowering the rate at which it burns calories.

Very low calorie diets are also short on nutrients, she said.

"Vitamin and mineral supplementation is needed on such diets, which is never as good as getting the nutrients from food."

Copyright AAP 2014.