Low-carbohydrate diets may appear effective when it comes to weight loss, but they could be linked to higher levels of LDL or 'bad' cholesterol levels, say scientists.
The findings, published in the February 13 issue of JAMA Archives of Internal Medicine, have been drawn from an analysis of five previous clinical studies that compared low-fat to low-carb diets.
Out of around 450 people who took part in the studies, those on low-carb diets lost weight faster than those on low-fat diets, but had increased total cholesterol levels and LDL levels. However, they also had lower triglyceride levels and higher HDL or 'good' cholesterol levels.
And although weight fell off faster from those consumers avoiding carbohydrates, after a period of 12 months both groups had the same blood pressure, completion rates and weight loss levels, said scientists at the University Hospital Basel in Switzerland
"We believe there is still insufficient evidence to make recommendations for or against the use of low-carbohydrate diets to induce weight loss, especially for durations longer than six months," the authors wrote. "The differences in weight loss between low-carbohydrate and low-fat diets after 12 months were minor and not clinically relevant."
As the popularity of low-carb diets surged with the appearance of the once-trendy Atkins diet, people trying to lose weight- 45 percent of women and 30 percent of men at any one time, according to the authors- increasingly turned away from the generally recommended low-fat, calorie restricted diet.
But because low-carb diets contain large amounts of protein and fat, concern remains about their effect on cholesterol levels and the cardiovascular system, said the researchers.
Indeed, if too much LDL cholesterol builds up on the inner lining of arteries, these can become more rigid and blocked, increasing the risk of heart disease.
And because no trials have yet examined the risk of heart attack or death in people on low-carb diets, it remains unclear whether the beneficial effects low-carb diets appear to have on HDL and triglyceride levels cancel out their apparent negative effects on overall and LDL cholesterol levels, said the authors.
"In the absence of evidence that low-carbohydrate diets reduce cardiovascular morbidity and mortality, such diets currently cannot be recommended for prevention of cardiovascular disease," they concluded.