Primary schools in England are failing to give children consistent messages about healthy eating, inspectors warn.
Is the healthy eating message getting across?
Meals provided in schools do not match healthier diet lessons taught in class, inspectors from Ofsted and the Food Standard Agency found.
As a result, children's awareness of diet and nutrition is poor and what they do learn makes little impact on their choice of food and drink.
The findings come as concern increases over the obesity "time bomb".
In the UK, it is estimated that one in five men and a quarter of women are obese, and that as many as 30,000 people die prematurely every year from obesity-related conditions.
In May, the Commons Health Select Committee attacked the government, food industry and advertisers for failing to act to stop rising levels of obesity and it said improving children's eating habits was the key to tackling the problem.
But a separate survey from the Department for Education, also published on Tuesday, shows that even when pupils are offered healthier food - only one pupil in 20 chooses a salad or vegetable option.
Ignorant of facts
The findings of the Ofsted and FSA report - based on visits to 25 English nurseries and primary schools - present a worrying picture of how the healthier eating message is being conveyed to young children.
Teachers and other school staff involved in food and nutrition education lack the necessary knowledge, the report says.
"This lack of accurate and up-to-date subject knowledge is a key factor in impeding effective food and nutrition education," the report warns.
"In the survey, staff frequently stated that the popular press was their source of nutrition information."
Too much choice
Inspectors also raise concerns about the sorts of foods on offer in school canteens, saying "the meals provided in most of the schools did not complement sufficiently the healthy eating messages that the teaching sought to convey."
The report noted that while schools did offer pupils a choice of food, this was not always helpful for furthering the healthy eating message.
"Children often chose nutritionally unsound meals when they were left to select without any guidance, and younger children frequently found too much choice overwhelming, tending in these situations to choose those food with which they were most familiar."
Five portions of fruit and vegetables should be consumed daily
Children at the back of the lunch queue were also found to have less choice than those nearer the front.
More positively, the report found that nursery schools were much better than primaries at promoting healthy eating habits.
Chief inspector of schools David Bell said: "Food fads and foibles are developed at an early age, so it is important that we help encourage and educate children about healthy eating habits at the earliest stage possible."
"We highlight some serious concerns about the type of food offered to children during school mealtimes which often does not reflect the good work done in the classroom."
Vivianne Buller, chair of the Local Authorities Caterers' Association, said the healthy eating message had to incorporate parents and the wider community.
"In defence of school meals, there's a greater possibility that a school lunch is more healthy than the average packed lunch being brought in from home," she said.
"One of the problems we have is the food offered - if children don't recognise it because they don't eat it at home, it can be very difficult to introduce unfamiliar food.
"But it is fair to say that schools haven't taken enough interest in school meals."
The report was published as the Department for Education and the FSA put out a report called School Meals in Secondary Schools in England and the results of a consultation Getting to Grips with Grub.
The studies suggest the majority of secondary schools are meeting nutritional standards and that progress is being made to improve the choice and nutritional quality of food in schools.
However, in line with the findings of the Ofsted and FSA report, the research indicates that what is being learnt in the classroom is not necessarily being reflected by young people's choices in the canteen, with unhealthy options being favoured over healthy food.
The survey of 5,695 11 to 16-year-olds at 79 secondary schools showed just 6% of pupils chose a salad or vegetable option.
This was despite the fact that 91% of schools included fruit and vegetables on their menus most days of the week and 83% met official nutrition standards all the