Low-carbohydrate dieters get most of their energy from protein and fat, with the Atkins diet amongst the best known regimes. Concerns have been raised in the past about the effect of low-carb diets on blood lipid levels and the risk of heart disease.

The international team of researchers from Switzerland and the US looked at five trials comparing low-carbohydrate and low-fat diets published since 2003, with a total of 447 people and analysed weight loss, and blood levels of cholesterol and triglycerides.

“Low-carbohydrate, non-energy restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to one year,” wrote lead author Alain Nordmann in the Archives of Internal Medicine (Vol. 166, pp. 285-293).

After six months, people on the low-carb diet lost, on average, 3.3 kg more than those on the low-fat diets. However, after 12 months there was no significant difference in terms of weight loss between the two types of diet.

Indeed, the volunteers on the low-carbohydrate diet had higher levels of both total cholesterol and low-density lipoprotein (bad) cholesterol.

However, the researcher did observe that that triglyceride and high-density lipo-protein cholesterol values were more favourable for the low carb dieters after six months.

On the basis of this meta-analysis, there appeared to be no clear benefit of either diet on heart disease risk factors, with both diets producing positive and negative results.

“The unfavourable changes in low-density lipoprotein cholesterol levels caution against the conclusion that low-carbohydrate diets can be generally recommended to promote weight loss,” wrote Nordmann.

The study supports previous nutritional concerns about low-carbohydrate, high-fat/protein diets, with many experts warning against long-term complications. And yet is also confirms claims that short-term adherence to the same-diet does result in weight loss.

Researchers from the University of Oxford presented a study at the last American Heart Association conference (November 2005) reporting that following the low-carb diet decreased the heart's energy stores by about 16 per cent.

“In contrast, trials of reduced-fat diets, in conjunction with other lifestyle modifications such as increased physical activity, have demonstrated long-term maintenance of weight reduction and delayed on-set of diabetes,” concluded the researchers.

The European Commission says that 14 million Europeans are obese or overweight, of which more than 3 million are children. Worldwide over 300 million people are obese, according to the International Obesity Task Force.