Controversy surrounding Redux has put diet drugs in the dock. Are they safe? asks Eleanor Bailey
We treat diet drugs like we treat celebrities - build them up to shoot them down. Redux, the latest weight-loss wunderkind, is a Hugh Grant. Hugely exalted at first, completely trashed after some dodgy stories, but ending up moderately effective in the right circumstances, although not the salvation of the British film industry (nor the end to excess weight) that was originally promised.

Right now, Redux is facing its Divine Brown. It is to be hauled before the Federal Drugs Administration in the US in April for a re-examination of its safety, following claims by scientists in America that it has caused brain damage in mice and heart problems in humans. Scientists here see this as the typical backlash to a drug that was over-hyped in the first place.

"Redux, or Adifax as it's known in the UK, has been used in Europe for seven years without any serious difficulties. Incidence of complaints is tiny," says Dr Nick Finer, director of the obesity clinic at the Luton and Dunstable Hospital. "It's like it was with Prozac. Everybody got very excited, then there was a rush of negative stories and 'Victims of Prozac' was created. Then it settled down again."

Weight-loss science will always be a battle of conflicting interests. The drugs are developed to fight obesity and meant for people whose weight puts them at risk of problems such as heart disease, diabetes, arthritis and hypertension. For such people, the risks of a diet drug are paltry in comparison. But weight-loss drugs appeal to the rest of us who want to lose just a few pounds or more.

Doctors can say this is a misuse, but in the quest for the perfect size 10, they go unheard. And while there's huge demand (prompted by big ad campaigns and hysterical media stories), there will be doctors who will prescribe, even if it is unethical. The Royal College of Physicians is due to publish a report with suggestions on appropriate use, the key finding being that they should not be sold for "cosmetic use".

But despite stories of death by diet drug, many experts believe that while they won't offer a healthy person any benefits (apart from unnecessary weight loss), they are unlikely to do any damage. Side-effects possibly, brain damage no. "There is risk involved with taking any drug," says Finer. "But if you look at drugs such as common painkillers, they carry higher risks than appetite suppressants or anti-obesity drugs. They are far better tested than many health supplements. I am much more worried about the health effects of people taking excessive vitamin D and cod-liver oil. But I would never condone taking them unless you have the illness of obesity." Finer maintains that alleged links to deaths are hugely anecdotal. Obese patients run a health risk and it would not be unexpected for some of them to die during a course of treatment from obesity- related problems.

Two key studies cited as saying that Redux is dangerous are flawed, according to Professor Michael Lean, professor of human nutrition at the University of Glasgow. A French study claimed that Adifax, licenced in the UK in 1990, caused pulmonary hypertension, which can lead to fatal heart failure. "In this study, all the subjects on the drug were obese, and primary pulmonary hypertension is a common health problem in obese people anyway," says Lean. "The control subjects were not obese and therefore unlikely to be at risk of the condition." The other headline-provoking American study, by Michael Molliver at the John Hopkins University in Baltimore, which linked the drug to brain damage in mice, was also unrealistic, says Lean. "The test involved feeding extremely large quantities of Adifax to the animals over a long period of time." No damage has yet been seen in humans. Adifax is licensed for use for a three-month period, but there are calls to make it available indefinitely.

But whether or not they cause long-term damage, health professionals still worry about inappropriate prescribing of the drugs to shape-obsessed, healthy young women. Research by Tom Sanders, professor of nutrition at King's College London, confirms that it is very easy for a person of normal weight to go to a slimming club and be prescribed appetite suppressants, thyroid hormones and diuretics with few or no questions asked. Two years ago, the Medicines Commission in the UK considered making it a criminal offence to prescribe to patients with a Body Mass Index (BMI is a person's weight in kilos divided by the square of their height in metres) of less than 35. The step was not taken but the threat sent tremors through the pharmaceutical industry.

Lean says that the cut-off is quite simple. "Women with a waist measurement of more than 35in and men with a waist measurement of over 40in are seriously overweight, risking their health, and could benefit from drug treatment." People find it hard to swallow that these treatments are for the very overweight. We want something for that extra half a stone. There is no drug registered for people who would just like to be a bit thinner, because nothing beats healthy diet and exercise. Science can't condone research for a drug for people who have nothing wrong with them.

Treatment can be divided into two groups. The first acts on the appetite- controlling serotonin in the brain, switching off hunger. Fenfluramine was developed in the Sixties (side effects include severe drowsiness). Dexenfluramine is effectively mark two. A purer form, it includes Redux and Adifax. It doesn't make you drowsy, but can cause a dry mouth, mood swings and light-headedness. The other group acts like a low-dose amphetamine, known as Diethylopropion and Phentermine, stimulating neurones to speed up the body's energy consumption. These are mild stimulants, which can increase the heart rate and make people feel high.

While a number of new drugs are in development, only two will be available soon. Sibutramine - which is likely to be approved by the FDA in a few months and later over here - was developed as an anti-depressant but was found to affect noradrenalin as well as as serotonin in the brain. Orlistat, in the final stages of clinical trials, works by preventing some of the fat eaten from being consumed by the gut. It blocks lipase, (the chemical in the gut that breaks down fat, allowing it to be absorbed), so that 30 per cent of fat passes out of the body.

"The breakthrough with Orlistat is that it, too, is passed out of the gut," says Dr Stuart Dollow, senior medical advisor at Hoffman-La-Roche, which is creating the drug. "Other drugs pass into the bloodstream and act on the central nervous system, suppressing the appetite." Also tested but not licensed here are Thermogenic drugs, which increase energy expenditure. Unfortunately, the more effective the increase, the bigger the side effects.

But these developments don't seem to be making society any lighter, 17 per cent of British women are obese. Fifty per cent of Britons are overweight with a BMI of more than 25 and rising. Professor John Garrow, retired professor of human nutrition at St Bartholomew's Hospital, says no diet drug has ever been truly beneficial.

"After six months of placebo- controlled trials, people five stone overweight on the drugs would lose about a third of their body weight, or 10kg. The subjects on the placebo, just controlling their diet, would lose 7kg. Over the next months, they'd lose another half a stone and that would be about it. If you are five stone overweight, you need to lose four stones, at least - and maintain that weight. No available drug can do that."

'I'm not worried about the risks - it's heaven to be thinner'

APRIL DA SILVA, above, is a 45-year-old, singer and actress who takes Redux

"I was going through a divorce and wanted to get my life together. I had Redux and B12 injections to speed up my metabolism. After eating badly for six years, I started eating sensibly. I'd tried so many diets: the protein diet, WeightWatchers, Slimfast, Pineapple diet, - starvation. Whenever I lost weight, it always came back. Eating was a comfort, a protection against pain, hurt and low self-esteem.

"I paid $90 a session in the US, which is cheaper than here. I started taking the Redux twice a day in October. I had no side effects, no mood swings, no dry mouth. I was able to sleep and didn't feel stressed. I just had a bit more energy. After three months, I lost close to 20lbs. I was 18 stone and now I'm 13st 7lb. Between 10st and 11st will be just right for my 6ft height.

"Soon I will be too close to my target to carry on taking it. My only fear is that I will find it hard to carry on losing weight once I stop. But I am determined. I will keep up my exercise. My daily diet now is a lot of fruit and Ryvita, butter and smoked salmon for breakfast, a litre of water and blended fruits during the day and a healthy evening meal at night. If I have a craving for chocolate, I don't stop myself.

"It's heaven to be thinner. I look about 30 to 35. I'm more alert. I'm not worried about risks. I was worried about getting palpitations and so on, but I'm not any more. I think that it's wonderful!"

ANNE-MARIE FIELDS, 30, (not her real name) was prescribed Ponderax at a London clinic

"I know I'm not obese, but I hate my shape. I was 13 stone but I got down to 10 stone. I couldn't shift the last stone and knew I couldn't like myself until I was my ideal weight. So, I went to a slimming place in London recommended by a friend.

"The doctor asked me a lot of questions about my health. And he asked why I wanted to lose weight - he said I didn't need to. But I convinced him that it was making my life miserable (I used to be bulimic) and he prescribed Ponderax. I lost an extra stone in two months, which is great, but I still feel I could look better. It didn't do any harm but I felt a bit spaced out. I don't think it helped my self-esteem.

"When I came off the drug, I felt very depressed for a while and reverted to old eating habits. I've put half a stone back on in six months, but I'm still ahead. If I go a stone overweight again, I'll probably go back to the treatment, because I can't see any harm in it, apart from the expense - it cost me pounds 150."