Children must be taught to cook healthy meals at school, the Liberal Democrat conference in Bournemouth has agreed.
The Lib Dems say children should have two hours of PE each week
Health spokesman Paul Burstow said the party would also guarantee children had at least two hours of physical exercise at school each week.
The measures were outlined as part of a "preventative approach" to health.
Mr Burstow pledged to "bring back lessons on healthy eating and cooking so we stop turning out couch potatoes and microwave chefs".
Mr Burstow added that the NHS should "treat prevention as seriously as cure" and outlined plans for MoT-style screening and free eye and dental tests.
But he also insisted that people should be helped to look after their own health more carefully.
He told the conference: "If the acceleration in childhood obesity witnessed over the past decade continues unchecked by 2020, more than half the nation's children will be obese.
"Our best hope for the future is to win the hearts, minds and taste-buds of today's children.
"At present, the curriculum focuses too much on turning out the next generation of food technologists, equipped to design the fast foods of the future but ill-equipped to cook a healthy meal at home."
The party would guarantee a minimum two hours' a week physical exercise in schools as well, he said.
The government's current aim is for 85% of children to have that amount of PE by 2007.
Other measures agreed at the conference included a "traffic light" food labelling system to warn of harmful fat levels and additives, and giving local and regional NHS bodies control over what happened in their area.