Pharmacological interventions

The pharmaceutical industry is racing to provide new products to tackle obesity.

The first phase of medical weight control is usually attempted through lifestyle changes: encouraging and supporting patients to adapt their eating and exercise patterns to take in fewer calories and use up more energy.

If this approach is not successful, pharmaceutical remedies are available, but these are far from ideal: there is no such thing as a magic slimming pill.

Drugs that do work have to be taken long term, just like agents used to control blood pressure or cholesterol levels. Weight-lowering prescription drugs are available in the UK, but, like all drugs, may have side-effects that need to be weighed against their potential benefits.

The two most commonly used are sibutramine and orlistat (Xenical). Sibutramine acts on the brain, making a person feel full sooner or for longer, while orlistat reduces fat absorption in the gut.

The past

Other drugs, or combinations of drugs, have been used in the USA in the past – most famously the 'fen–phen' combination (fenfluramine and phentermine). Individually, fen and phen were approved for use as appetite suppressants, for short periods (a few weeks). Later, they began to be used together and for much longer periods. Then the trouble began.

On 8 July 1997, the Mayo Clinic reported that 24 patients had developed heart valve disease after taking fen–phen. Other cases soon appeared, and the drug was rapidly taken off the market. American Home Products (AHP), makers of fen-phen, agreed to pay $3.75 billion in compensation to thousands of people who used the diet drugs.

The future

Clearly there's a demand for new weight-lowering drugs, and companies still are looking into these. One promising new drug, rimonabant, seems both to reduce the craving for food and help people stop smoking, by acting on a particular class of cannabinoid receptors in the brain.

These receptors respond to the psychoactive component of cannabis, chemicals known as cannabinoids. It was noticed that smoking cannabis caused 'the munchies', and this led to a search for drugs that block cannabinoid receptors and reduce appetite.

The next few years are likely to see many more products hit the market, targeting different points in the body's weight control system.