Robert Atkins, the weight-loss guru whose diet books sold in their millions, has won posthumous backing for his controversial theory about how to lose weight.

The first randomised controlled trial comparing his high-fat, low-carbohydrate diet with a conventional low-fat eating plan found people on the Atkins diet lost weight quicker and had improved levels of blood fats, with increased amounts of "good" cholesterol.

The finding will surprise the medical establishment which has long argued that the Atkins diet was potentially damaging to health and could affect kidney function and raise "bad" cholesterol levels.

But it will delight his many fans, including the Friends actresses Jennifer Aniston and Courteney Cox Arquette.

Atkins - who died last month - based his diet on the theory that eating carbohydrates made susceptible people pump out insulin, which encouraged them to put on weight. His diet eschewed carbohydrates in favour of calorie-dense fat and protein - meat eggs and cheese - violating what doctors had long believed about healthy eating.

Eating calorie-dense fat is what makes people fat, doctors said, and eating saturated fat was dangerous.

But researchers from three American Universities who studied 132 obese people who were an average of 50lbs overweight have challenged that conventional view. As well as losing weight faster, those on the Atkins diet were healthier.

The findings, published in the New England Journal of Medicine, will open up a debate over whether a low-fat or low-carbohydrate approach is the best way to lose weight. A key question is why cutting down on carbohydrates should have more effect than cutting down on fat.

Samuel Klein, a researcher at the Washington University School of Medicine in St Louis, suggested a possible answer. "This study demonstrates that a low-carbohydrate diet can have beneficial effects in treating obesity. A calorie is still a calorie, whether the calorie comes from fat, carbohydrates or protein. But it might be that certain types of calories are more filling than others and result in an overall decrease in total calorie intake," he said.

At three months, those on the Atkins diet lost an average of 17.6lbs while the conventional dieters lost about 8.3lbs. After six months those on the high-fat plan had lost an average of 21.2lbs compared to 11.5lbs lost by those on the normal diet.

At 12 months the Atkins group was down an average of 15.9lbs versus 9.7lbs among the conventional dieters.

However this was not considered statistically significant, partly because almost half of the trial participants had dropped out of the study before the 12-months mark.

Overall, the Atkins dieters had higher levels of good cholesterol and lower amounts of triglycerides, which are harmful fatty substances in the blood. The research was carried out by University of Colorado, the University of Washington and the University of Pennsylvania. The study team are now recruiting more people for a five-year study of low and high-carbohydrate diets.

Dr Atkins published his first book, Dr Atkins' Diet Revolution, in 1972. A series of titles followed, with Dr Atkins' New Diet Revolution selling more than 10million copies. He died, aged 72, after banging his head on a New York pavement.