Combining the best components of low-carbohydrate and low-fat diets could be the most effective way to lose weight and keep it off, a leading obesity expert said.

ow carbohydrate diets such as Atkins, which largely exclude fruit, vegetables and grains, produce a greater weight loss initially than reduced-fat plans but in the long-term they are no better and may have side effects.

Professor Arne Astrup, of the Institute of Human Nutrition in Copenhagen, Denmark believes adding the best aspects of both could be the answer.

"Combining some of the good things from the low carb with the good things from the low fat diets seems to be satiating and also to enhance weight loss," he told the European Congress on Obesity.

The more extreme the diet is, the less likely people are to adhere to it, he added.

"You cannot live without carbohydrates for years."

Astrup and his colleagues, who carried out a comparative study of different diets, also found side effects such as diarrhoea, muscle weakness and dehydration in people on low carbohydrate diets.

"In the long-term we fear that this low intake of fruits and whole grains could increase the risk of colon cancer," he added.

Studies have consistently shown that a 10 percent reduction of fat in the diet produces weight loss in overweight and obese patients, according to Astrup.

His suggestion for the optimum diet was 25-30 percent of calories from fat, between 15-25 percent from protein in the form of lean meat and dairy products and 45-55 percent from carbohydrates consisting of fruit, vegetable, whole grains and legumes.

The popularity of low-carb diets which encouraged people to shun bread and pasta in favor of protein such as meat and cheese has faded. In Europe the low glycemic index (GI) diet has become popular.

GI measures how efficiently the body can metabolise carbohydrates. It ranks carbohydrates by how much a person's blood sugar rises immediately after eating.

Starchy foods such as white bread, rice and potatoes tend to have a high glycemic index while whole grain breads and pasta and legumes have a lower GI.

However, Astrup said there was little evidence that low GI foods were better than high GI foods for weight control.

Despite a multi-billion dollar diet industry, the number of overweight and obese people is increasing worldwide. Thirty percent of adults, 60 million people in the United States alone, are obese. European countries, where rates range from 10-25 percent, are not far behind.

About 2,000 delegates from 80 countries are attending the four-day meeting.