The controversial Atkins diet, favoured by many celebrities, may be as safe and effective as low-calorie weight-loss plans, researchers say.
Brad and Jennifer are said to be Atkins devotees
People on the Atkins diet are allowed unlimited amounts of proteins and fats but have to restrict their carbohydrate intake.
Some experts are concerned that although this leads to short-term weight loss, the Atkins diet is not balanced, and can lead to long-term kidney damage in some.
US researchers looking at 63 obese men and women aged 44 who weighed, on average, 216 pounds.
They were divided into two groups; those in the Atkins diet were asked to follow the diet's plan while those in the conventional group were told to eat a diet of 60% carbohydrates, 25% fat and 15% protein.
Such diets may not have the adverse effects that were anticipated
Professor Gary Foster of the University of Pennsylvania
Men were limited to 1500 to 1800 calories a day, and women to 1200 to 1500.
They were assessed by a dietician after three, six and 12 months.
In the early stages, those on the Atkins diet lost twice as much weight as those on the conventional eating plan.
At three months, the Atkins group had lost an average of 17.6 pounds, compared to an average of 8.3 pounds in the other group.
After six months, they had lost an average of 21.2 pounds compared to 11.5.
'No adverse effects'
After a year, the difference between the two groups was narrower.
The Atkins group had lost an average of 15.9 pounds compared to 9.7 pounds in the other group - but the researchers say this figure is not statistically significant as almost half of the participants had dropped out of the study by this point.
But those on the Atkins diet had seen a much greater increase in their levels of HDL or 'good' cholesterol.
They also saw greater falls in triglyceride levels - a type of fatty acid found in the blood.
Professor Gary Foster of the University of Pennsylvania, who worked on the study, said: "Widely recommending low carbohydrate approaches may be premature, but our initial findings suggest that such diets may not have the adverse effects that were anticipated.
"The real issue is whether low carbohydrate approaches help patients maintain their weight loss better than conventional approaches.
Diet guru Robert Atkins, who died in April
"It will also be important to determine whether the effects of the diet on cholesterol are the same during weight maintenance as they are they are during weight loss."
A second study of 130 patients carried out by researchers at the VA Medical Center in Philadelphia found a low carbohydrate diet was linked to greater weight loss and reductions in triglycerides and improvements in insulin sensitivity compared to a low-fat diet.
Fast weight loss
Catherine Collins of the British Dietetic Association said the initial stage of the Atkins diet involved cutting out virtually all carbohydrates - dieters are allowed to eat no more than 20 grams a day which must come in the form of salad greens and other vegetables.
No fruit, bread, pasta, grains or starchy vegetables are allowed during this period.
She said this, combined with the fact that dieters' bodies would then use up energy from carbohydrates, stored as glycogen in the liver and muscles, meaning people lost weight quickly.
Atkins dieters are later allowed to introduce small amounts of carbohydrates, but Ms Collins said: "If people know they are going to be checked, they could go back to this more intense diet so they could lose weight quickly."
But she said the finding on HDL cholesterol was interesting.
She added: "On the face of it, this study suggests the Atkins diet isn't that bad, but more research is certainly needed."
The research is published in the New England Journal of Medicine.