LONDON: Three diet drugs recommended for long-term use result in minimal weight loss and carry some serious side effects, a review of research found.

Though most users of the drugs remained overweight, experts said the drugs could help curb the dangers of obesity by reducing rates of heart disease, diabetes and other health problems.

In a paper published today in the British Medical Journal, researchers in Canada and Brazil analysed existing data on three popular weight-loss drugs: orlistat, or Xenical; sibutramine, known as Meridia in the United States and Reductil in Europe; and rimonabant, or Accomplia.

Scientists found that patients on the drugs - men and women between 45 and 50 years old who weighed about 100 Kg and had a body mass index of about 35 - lost less than 5 kg on average. The study participants used the drugs for periods of between one and four years.

"Drugs are not the magic cure and are not for everybody," said Dr Raj Padwal, an assistant professor at the University of Alberta in Canada, one of the paper's authors. "But in specific patients, they have great benefits."

Padwal and colleagues considered 16 trials that tested orlistat, which involved 10,631 people. Orlistat, which works by preventing fat digestion, helped people lose about 3 kg on average. But it also reduced diabetes and improved their cholesterol levels and blood pressure. Up to 30 per cent of patients had unpleasant digestive and intestinal side effects, such as incontinence.