Follow the cash diet

Can't lose weight? What if the NHS paid you for every pound shed? Money can can work where willpower fails, discovers Jeremy Laurance

A new weapon is being deployed in the battle to persuade people to change their unhealthy behaviour – by targeting them in the pocket. If people cannot be persuaded to stop smoking/lose weight/get more exercise for their own good – then why not pay them to do so?

Obese patients in Kent have been paid up to £425 to lose weight by the NHS in a trial to test whether financial incentives can be used to change unhealthy behaviour. In Essex, pregnant women who smoke have been offered up to £60 in food vouchers on the NHS if they give up. In west London (Hammersmith) and in Bournemouth the NHS is offering people under 25 a £10 HMV voucher to have a (free) home chlamydia test.

Some claim it is a revolutionary approach. Others dismiss it as simple bribery. The criticism has not deterred other countries from trying the approach. One of the highest rewards was offered to employees of General Electric in the US who were paid up to $750 (£500) if they gave up smoking and remained abstinent for at least 12 months. There was a sliding scale of payments, which rose the longer the individual stayed tobacco-free.

General Electric's largesse has now been topped by a private UK company, Weight Wins, which ran the trial weight-loss scheme in Kent for the NHS. For a £90 initial payment and a £20-a-month subscription – "similar to what you would pay to join a gym", the company says – individuals who sign up to lose the maximum 150lbs (an impressive 11st) over 21 months will be paid £1,750 if they can keep the weight off for at least three months, more than tripling their investment.

Winton Rossiter, founder of Weight Wins, says: "We are offering new hope to dieters. Most people know how to lose weight, but they fail to maintain their weight loss because of a lack of motivation. Providing a structured financial-incentive programme is the key to helping our participants develop healthy lifestyles for the long term and to losing weight and keeping it off."

Defenders of schemes like these say paying people to change their habits works because it offers immediate rewards for behaviour that will otherwise only provide a benefit in terms of improved health years ahead. The approach was recommended last year in a report by Health England, a government quango chaired by the former No 10 health adviser, Julian Le Grand.

Professor Le Grand, a health policy expert at the London School of Economics, says: "One of the main problems facing both individuals and the Government is that we reap the costs of unhealthy activities in the future whereas we experience their pleasures and benefits today. The 18-year-old smoker does not think about dying of lung cancer at 60. Policies have to be developed that bring some of the costs of unhealthy activities – or the benefits of healthy ones – 'back from the future'."

The idea of offering cash payments to promote health originated in the developing world, where it has been successfully used to encourage one-off responses, such as attendance at clinics or uptake of vaccinations. But changing behaviour has proved harder. A review of 17 trials of the use of payments to help people give up smoking found the effects only lasted as long as the incentives were paid. Similarly, nine weight-loss trials showed no benefit from payments after 18 months.

The NHS is not involved in the new Weight Wins public programme but it has been involved in others, including the trial in Kent and the smoking trial in Essex. This has drawn criticism from the Conservative MP Ann Widdecombe. Ms Widdecombe, who lost 35lb on ITV's Celebrity Fit Club show in 2002, says: "If the NHS had money to spare it would be OK, but the fact is the NHS is short of money. There are plenty of people who cannot get funding to pay for treatment for illnesses. We can all control our own weight. If the NHS has to prioritise, then this should be the last of its priorities."

The National Obesity Forum is similarly sceptical, saying: "We would only support this if there were a proper randomised controlled trial that proved that weight was being kept off."

New ideas to help people change their behaviour are urgently needed not just for their health but for economic reasons, too. The NHS is estimated to spend more than £4bn annually on treating obesity and related illnesses. Mr Rossiter of Weight Wins claims that its cash payments programme could save the NHS £1.7bn in lifetime medical expenses for every million people taking part. At least 30 million adults in Britain are estimated to be overweight or obese.

Theresa Marteau, professor of health psychology at Kings College, London, reviewed research on financial incentives in a study published last year in the British Medical Journal. "The theory is that much of our behaviour – 45 per cent – is habitual," she says. "The idea of incentives is to help break bad habits and, once the new habit is established, the incentive can be removed. But, unless you change the environment, the chances of success are reduced."

She adds: "This is about understanding human frailty. Most people don't want to be overweight or keep smoking, but find it difficult to do anything about it. If we can kick-start a change in their habits then that is good for them and for the rest of us."

Professor Marteau said the failure of incentives to change behaviour in the long term could be because the schemes were not sophisticated enough. "Very few schemes tried to incentivise sustained behaviour change. If the incentives were more nuanced, it is possible they would be more effective. The General Electric scheme for giving up smoking offered large incentives that were incremental the longer the smoker had given up. It is clever, building on behavioural principles. The results are promising but they need replicating in other studies."