Healthy eating lessons should be compulsory for all children up to the age of 16,delegates at the Association of Teachers and Lecturers' annual conference in Gateshead said.
Teachers said classroom time for cookery lessons had been slashed since the introduction of the national curriculum 18 years ago.
"As a result, we have a whole generation who can't and don't cook, and who are bringing up children with no knowledge of good diet, hygiene, creative cookery or even basic cooking skills," said Kay Ingham, a teacher from North Yorkshire.
Teachers warned that the cuts cast doubt over whether the Government could deliver its £270m drive to promote healthy eating in schools.
They argued that lessons in a healthy lifestyle would help cut obesity among the next generation and make pupils more attentive in their classes.
Ministers are introducing new nutritional standards for school dinners from September, and are planning a ban on school vending machines selling junk food such as crisps and sweets.
However, delegates argued the drive would not work unless there was a set period in the timetable to teach healthy eating habits and teachers were given special training on how to deliver them.
Ms Ingham said: "Practical cookery lessons in many secondary schools seem to have become less and less frequent.
"We need properly qualified teachers who can motivate pupils as to how they should radically change their lifestyles and take the healthy option."
She added: "With vigorous teaching and special quality rooms for food preparation, we can look forward to slimmer, healthier, better-tempered, less hyperactive pupils."
Delegates also warned that children as young as five were losing time for creativity and play as a result of the rigid testing regime. Many schools were introducing their own tests for six-year-olds to prepare them for those demanded at seven under the national curriculum.
Rosemary Readman, a primary teacher from North Yorkshire, said that before the introduction of the national curriculum, half a day each week had been set aside for food technology lessons, enough time to prepare dishes.
Now they were only compulsory up to the age of 14, and had to be crammed into half an hour. "That's not enough time to prepare an apple crumble," she said.
The conference also heard that the content of food technology classes was only one-third practical, with two thirds of teaching based on theory.
Parents were often standing in for teachers because home economics staff had been axed as a result of the downgrading of the subject.
Ms Readman appealed to television soaps like EastEnders to join the fight to change children's eating habits for the better, adding: "Why not have Pauline Fowler creating a meal with fresh vegetables?"
Ministers argue that they have earmarked £270m to improve school dinners and promote healthy eating. Much of the cash has gone towards training school canteen staff in the production of healthier school meals.
The Education Secretary, Ruth Kelly, has insisted providing healthier food options should be a top priority for schools.Reuse content