More than 50 per cent of 15 year-olds in one council area will die before they reach 65 if healthy eating options are not enforced in schools.
Steps to limit children's choices of food may have to be taken if their nutritional health is to improve, the senior chief inspector of education has warned.
Graham Donaldson applauded the progress made in many primary and special schools under the Hungry for Success policy of the previous Scottish Executive.
But he accused secondary schools of a "lack of urgency" in their implementation of the policy since it was launched in 2003.
Childhood obesity had continued to grow in parallel with healthy eating initiatives. This suggested that the schools' healthy eating programme on its own was not sufficient to tackle the long-term problem, he said.
Eating patterns outwith school also had to change, and parents, shopkeepers and food outlets, food manufacturers and elected representatives had to live up to their responsibilities, Mr Donaldson said at the launch of HMIE's report Hungry for Success - Further Food for Thought in Glenburn School in Greenock. He welcomed the Scottish Government's national food policy, launched on the same day, as an attempt to address some of the bigger issues.
Ian Fraser, corporate director for education and social care at Inverclyde Council, said that, since 2003, school meals had been transformed in his authority. But he highlighted the health problems facing Inverclyde, which are the second worst in Scotland.
"Unless we do something, 55 per cent of our 15-year-olds in school today will die before they reach their 65th birthday," he said.
Nevertheless, he felt at a "crossroads" about how to drive forward the promotion of healthy eating. The concordat between national and local government had established free school meals for all P1-3 pupils from August 2010. However, he believed there had to be provision of breakfasts, lunches and, if necessary, teas for targeted children.
"We are trying hard not to turn our schools into prisons and to put young people in situations where they challenge authority. The legitimate demands for education to solve a societal problem, such as obesity, have to be balanced against individual human rights to assembly and association," he said.
Educating young people to make the right choices was key, he suggested. "A lot of people can be seen to be zealots of healthy eating, and life's not like that," he said.
Both Mr Fraser and Mr Donaldson called for better tracking of what young people eat throughout the day. "We do not have comprehensive information about what pupils actually eat at school lunches, as some may leave food or regularly select less healthy choices," said Mr Donaldson.
"Moreover, around 54 per cent of pupils choose not to take school meals. In addition, many of the pupils who do take school lunches supplement these with other food during the school day. There is a need to get a clearer picture of what children and young people actually eat over the course of a day."
Improvement in the nutritional quality of school meals;
Primary schools, in particular, have established healthy eating within the context of health promotion;
Better social experience at lunchtime;
More fruit and drinking water available;
More healthy choices in tuckshops and vending machines;
Examples of effective partnerships with parents.
Better pupil consultation in schools.
Food sampling and "taster" approaches were increasingly popular.
Some authorities had introduced mobile vans to sell their produce outside the school
A few primary and secondary schools use sweets as rewards;
Poor communication between senior managers and catering staff persisted in a number of schools;
A few primary schools and just under a quarter of secondary schools do not protect the anonymity of pupils entitled to free school meals and, in a few cases, secondary pupils entitled to free meals were further disadvantaged by not being able to use the pre-ordering system;
Long queues and ineffectiveness of rota systems put pupils off school dinners;
Schools were not, in general, good at self-evaluation when it came to measuring their progress under the Hungry for Success policy;
Information for secondary pupils about food and drink was limited;
Primary and secondary schools found it challenging to meet the nutrient standards for sodium, iron and saturated fatty acids; primaries struggled to meet standards for non-milk extrinsic sugars and carbohydrates; secondaries did not achieve standards for calcium and folate;
Pupils complained about food not being kept at the right temperature, soggy vegetables, over-cooked or burnt food, and changes in the quality of food, usually due to a change of supplier;
A few schools operated disincentives to healthy choices: for example, a ham and salad sandwich costs more than a ham sandwich.