Jeremy Laurance: A breakthrough – but the real answer lies in exercise and diet

The first of a new class of slimming pill is bound to attract attention, especially when it comes with the backing of a leading obesity researcher and is published in an internationally respected medical journal.

Anyone who has ever reached for a second cream cake, or a supersized-burger with supersized-chips, will have an interest in a medicine that can deal with the consequences – those extra pounds on the scales and inches on the hips.

But is it foolish to seek salvation in a drug when we know the real answer lies elsewhere, in a changed lifestyle built around more activity and less junk food?

The obesity field can seem increasingly dominated by drugs. Liraglutide (Victorza), the newest kid on the block, looks like a serious contender in the battle for domination of the hugely lucrative market. It is the fourth to be licensed in recent years, after orlistat (Xenical), sibutramine (Reductil) and rimonabant (Acomplia).

But the success of these drugs in reducing weight has been limited and the safety of some has been questioned. Rimonabant was withdrawn last year after it was linked to psychiatric disorders and suicides. By then it had been on the market for two years and almost 100,000 patients in the UK had taken it. An earlier slimming treatment, dexfenfluramine, was banned in the 1990s, after being associated with serious lung and heart effects.

The sheer numbers affected by obesity – more than two thirds of the UK population are either obese or overweight and 700 million are predicted to be obese worldwide by 2015 – mean that rare but serious side effects can take months or years to emerge.

Liraglutide's claimed advantage over existing treatments is that it cuts weight as well as the risk factors associated with heart disease and diabetes, such as blood pressure and poor glucose control. This could give it the edge over sibutramine, which raises blood pressure, and orlistat, which has unpleasant, although not unsafe, effects on the digestion.

But the arrival of a new class of drugs raises the question of what role medicine should play in the control of obesity. Some blame the obese for being lazy, indulgent and weak-willed, arguing that the NHS should not offer treatment to people who have brought their problems on themselves.

But doctors reject such arguments, recognising cutting off such people would empty their surgeries of smokers, alcoholics, people with sexually transmitted diseases and a host of other conditions. But they remain divided over the benefits of obesity drugs.

Some say that in seriously obese patients with other health problems in whom all attempts to lose weight have failed, even a 10 per cent downward swing on the scales achieved with the help of a drug can bring significant health gains.

Others point to the short-lived effects of the drugs, noted by the National Institute of Clinical Excellence, with most patients regaining the weight lost over the months and years after drug treatment ceases.

But what we can all agree on is that it is better to prevent problems in the first place than rely on medicine to cure them. We know what to do – walk, don't drive; eat an apple, not a cream cake. The challenge is how it is to be done.