Everything you know about weight loss guidelines may be wrong.

When it comes to keeping weight off, people who rapidly lose weight have just as good odds as people who lose weight at a steady pace, according to new medical research.

The University of Melbourne and Austin Health trial of 200 obese adults also found people who lost weight rapidly were more likely to achieve their target weight than lose who took a more gradual approach.

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The three-year study assigned participants to a 12-week rapid weight loss program with an average loss of 1.5kg a week, or a 36-week gradual weight-loss program with an average weight loss of 0.5kg a week.

Those in the first group were placed on a strict diet of just 400-800 calories per day, consuming mostly protein shakes.

Despite current dietary guidelines recommending weight loss at a steady pace, the research found those who lost weight quickly were less likely to drop out of the program. Both groups also gained weight following the study.

Co-author Katrina Purcell said the findings questioned the worldwide treatment of obesity.

“Global guidelines recommend gradual weight loss for the treatment of obesity, reflecting the widely-held belief that fast weight loss is more quickly regained,” Ms Purcell said.

“However, our results show that an obese person is more likely to achieve a weight loss target of 12.5 per cent weight loss, and less likely to drop out of their weight loss program, if losing weight is done quickly.”