PATIENTS on weight-loss drugs may lose little more than their money, a recent study claims. But they risk many unpleasant side effects.

An article in the British Medical Journal on Friday said close to 20,000 patients, weighing an average of 100 kgs, lost less than 5 kgs as a result of these drugs.

They had been on one of three weight-loss medicines for one to four years.

Associate Professor Tan Huay Cheem, head of the National University Hospital's cardiac department, agreed that while he has given them to patients, 'the mere taking of these anti-obesity medicines to reduce weight frequently fails miserably.'

But Dr Tan Chee Eng, a diabetes specialist in private practice, said the loss of these few barely discernible kilograms makes a significant difference for people suffering from diabetes or heart problems.

But he agrees that people who take the drugs for cosmetic reasons may not see much benefit.

Two of the drugs, Xenical and Reductil, are available here. The third, a newer drug called Accomplia, is sold in Europe but not in the United States or in Singapore.

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

The meta-analysis, which looked at data from 30 clinical trials, found that up to 30 per cent of patients on Xenical had unpleasant digestive and intestinal side effects, such as incontinence. They lost an average of 3 kgs.

Patients on Reductil lost 4 kgs and had improved cholesterol levels. But up to 20 percent suffered from raised blood pressure and pulse rates, insomnia and nausea.

Patients on Accomplia lost the most weight - 5 kgs on average. Their blood pressure and cholesterol levels also improved. The risk of mood disorders increased in 6 percent of patients.

Another study released on Friday by a different medical journal, The Lancet, found that patients on Accomplia were far more likely to suffer from depression, anxiety and, in severe cases, suicidal tendencies.

These drugs are meant for people who are severely obese. Many of them would suffer from, or are at high risk of, heart diseases or diabetes. Worldwide sales of these three medicines comes to US$1.2 billion a year.

The side-effects mentioned in the study are known and listed by the drug manufacturers, and taken into account by doctors using them.

Dr Tan said he prescribes Reductil to medically obese patients 'as a reward after they have lost weight through lifestyle changes' to help them maintain their new weight.

This is because, in spite of continued lifestyle changes, as people age, their weight will start inching up again.

Fat people who lose 4 kgs cut their risk of getting diabetes by a hefty 30-40 per cent, he said.

For those who already suffer from diabetes, this amount of weight loss 'significantly' cuts their blood sugar level and their risk of getting heart disease.