People who are overweight could be paid to get slim, the government suggested yesterday as part of its national strategy to tackle the obesity epidemic.

The strategy, to tackle what the health secretary, Alan Johnson, described as "the most significant public and personal health challenge facing our society", proposes measures involving schools, employers, the food industry, GPs and others which are intended to encourage individuals to eat better and exercise more.

Among those trailed by ministers, such as cookery lessons for children and urging local authorities to refuse permission for fast-food shops to open near schools, is a proposal to offer cash incentives to adults who need to lose weight.

Details of how this would work in the UK are not yet thought through. The cash incentives could be from employers who want to reduce sickness absence in the workforce or they could be from the government, via GPs. The idea comes from the US, where a study last September found that the more money people were promised, the more weight they lost.

Vouchers, instead of cash, could be used to reward people who lose weight, the document says, citing two pilot schemes from the British Heart Foundation. One was a competition between teams called Cold Turkey. The team that lost the most weight received a trophy. Fruit baskets were given to the team with the greatest percentage loss each week, and the teams lost an average of 8kg (17lbs) each. The second pilot, Biggest Loser, ran for eight weeks. The individual with the greatest percentage weight loss (6.4%) received £130 in vouchers.

Other measures in the strategy aimed at adults include making it easier for people to exercise by designing walkways, cycle routes and open spaces into towns and encouraging employers to offer fitness opportunities at work.

However, children are the primary focus because it is easier to prevent weight gain than to reverse it.

There was anger in some quarters at the government's attempts to come to a consensus with the food industry, in particular over labelling and junk food advertising on television before 9pm. In both cases, a long-running dispute has not been settled.

Betty McBride, of the British Heart Foundation, said: "The government is backing down from taking on industry in the fight against obesity. It is naive to expect voluntary compliance from an industry that is putting hundreds of millions of pounds into promoting these foods every year. Self-interest will always win out."

The children's commissioner, Al Aynsley-Green, called for "a firm commitment ... to introduce a 9pm watershed on junk food TV adverts to further limit young people's exposure to unhealthy foods".

There will be attempts to identify families whose children are at risk of obesity. The government plans a £75m campaign aimed primarily at helping parents of babies and young children to improve their diet and exercise.

Without action, almost nine in 10 adults and two-thirds of children will be overweight or obese by 2050 and at risk of diabetes, cancer, heart disease and other health problems, costing society £50bn a year, according to a recent report by scientists commissioned by the government.