Led by Joseph Proietto, Sir Edward Dunlop Professor of Medicine at the University of Melbourne and Head of the Weight Control Clinic at Austin Health, the study also found that substantial weight loss is more likely to be achieved if undertaken rapidly.
"This randomised study highlights the urgent need for committees that develop clinical guidelines for the management of obesity to change their advice," he said.
The trial included 200 obese adults (BMI 30-45kg/m²) who were randomly assigned to either a 12-week rapid weight loss programme (average weight loss 1.5kg a week) on a very-low-calorie diet (450-800 Cal/day) or a 36-week gradual weight-loss programme (average weight loss 0.5kg a week) based on current dietary recommendations.
Co-author and dietitian, Katrina Purcell said that the findings would impact 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. 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," she said.
The researchers found that the initial rate of weight loss did not affect the amount or rate of weight regain: with similar amounts of weight regained by 3 years by participants on both diet programmes who completed both phases of the study (around 71% in both groups).
The authors suggested a number of possible explanations for their findings including that the limited carbohydrate intake of very-low-calorie diets promotes greater satiety, and less food intake by inducing the production of hunger suppressants called ketones. Losing weight quickly may also motivate participants to stick to the diet.
The research was done in collaboration with La Trobe University.