Yet another study has been done on the high-protein, low-carbohydrate Atkins diet and this one has found that it can cause long-term damage to blood vessels, U.S. researchers reported on Tuesday.

Much research has been done on the Atkins diet, with some studies finding that it is effective in bringing about weight loss, particularly in women, and others finding that it is dangerous to cardiovascular health.

Until this most recent study, no one had looked at the maintenance phase of the diet, when the aim of the diet is not to lose weight but to maintain a steady weight.

This study, presented at this week's annual meeting of the American Heart Association, found that the diet increased "bad" cholesterol and other markers for heart disease.

Lead researcher Dr. Michael Miller, director of preventive cardiology at the University of Maryland Medical Center, says since weight loss brings heart benefits in itself, his team wanted to know how the cardiovascular system would fare on the high-fat diet when weight remained stable.

For the study, 18 healthy adults completed four weeks each on the Atkins diet (which contains 50 per cent of its calories from fat), the South Beach diet (with 30 per cent fat) and the Ornish diet (10 per cent fat). They were carefully monitored to ensure that they did not lose weight.

People on the Atkins diet had increased levels of LDL ("bad") cholesterol, more constricted blood vessels and an increase in blood markers for inflammation, which is linked to heart and artery disease, some by as much as 30 percent or 40 per cent, the researchers said.

The results were less clear for the Ornish or South Beach regimens. In those diets, markers for inflammation remained stable or dipped by up to 20 per cent, the researchers found.

Miller says he believes the Atkins diet is potentially detrimental for cardiovascular health if maintained for a long period.