BMI = w÷h²* The formula to beat obesity, claims SNP

Nationalists will vote this weekend to back regular weight and height tests for all primary school children.

The information will be used to calculate the body mass index (BMI) of every child in Scotland, which will be updated annually, allowing doctors and even teachers to work out which children are overweight or obese.

While the plan is in its early stages, the information could be used to develop early intervention plans at school, include special diets and exercise regimes. Parents would also be told.

The proposal received a cautious welcome from health experts and opposition politicians yesterday, but with warnings that the information had to be used sensitively to avoid stigmatising those children deemed overweight or obese.

Scotland has a poor record on childhood obesity and the situation is deteriorating. Recent figures showed more than a fifth of primary one children in Scotland were overweight, 8.5 per cent obese and 4.3 per cent severely obese.

By the age of 12, more than a third were overweight, including almost 20 per cent who were obese. The trend is expected to worsen.

Half of Scottish 13-year-olds take sugary drinks and eat sweets daily, while fewer than a quarter have vegetables daily.

The statistics have already spurred the Scottish Government into new measures, including a move towards free school meals for the early years of primary schools and more exercise time in the school day.

Despite this, Scotland has retained its place as the fattest nation in the UK and experts warn of a time-bomb, with large numbers of overweight children becoming obese in later life.

The SNP is poised to push the agenda even further on this issue at the party's Spring conference in Glasgow this weekend.

SNP insiders have told The Scotsman that the plan for BMI checks is likely to be passed.

Other plans in the conference motion include training for newly qualified teachers to help them spot and tackle obesity in children and "fun exercise classes" to persuade more youngsters to get active.

The Nationalist motion also calls for supervised "walk-to-school" systems for primary school children in an effort to get parents to park at organised drop zones away from schools where the children can be picked up by teachers and walked to school in groups.

At the moment, all children have their height and weight measured when they arrive at primary school and their body mass index is calculated.

However, this is done only once, and the information is only used for compiling national statistics. If obesity is detected, the child's parents are not told and neither is the school.

Dr Ewan Bell, a consultant specialising in adult obesity at Dumfries and Galloway Royal Infirmary, said there was little point assessing BMI if no follow-up action was taken.

He said the SNP plan was fine as a starting point, but the real impact would only be felt if the information was used properly and sensitively to tackle the problem.

"Just recording the data is useless," Dr Bell said. "It might give you an evaluation of the size of the problem but it has to be used sensitively to educate parents."

He said he believed the information should be shared with parents, to help them put together better diets for their children and help them get more exercise.

"You can't just have a queue of children waiting in line to be weighed, with some being told they are overweight. You have got to deliver the message in a very sensitive way," said Dr Bell.

"You don't want kids to get a complex or to be affected psychologically."

However, Jackson Carlaw, for the Conservatives, warned against the plan.

He said: "The last thing we need is primary school children being stigmatised and potentially bullied by their peers having been formally branded as 'obese' by the state."

Ross Finnie, for the Liberal Democrats, was cautiously optimistic. He said: "Annual health checks to help tackle the worrying rise in childhood obesity must come as part of a wholesale restructuring of health checks we give to young people."

Early intervention is best way to establish healthy eating habits

CHILDHOOD obesity is a growing problem in Scotland – about one in five primary one children are overweight, including nearly 8 per cent who are obese, a proportion which rises as they get older.

Obese children may be teased or find it hard to make friends, and the exercise which would help them to lose weight is harder to do. But these visible effects are just the tip of the iceberg – obese children are storing up health problems for the future.

But is calculating the body mass index of children the way forward? The information will certainly be useful, but then we have to consider how it's used.

We need to help children who are overweight, but we don't want them to feel stigmatised.

It's a very sensitive problem. Targeting every child – with initiatives designed to teach them all how to eat healthily, and make this easy and fun – seems to be the best solution.

It's good for everyone, whatever weight they are. But it's very hard to stand by and watch if a severely obese child appears not to be benefiting.

Parents have a big responsibility – they are important role models, and for younger children, they are the main food providers. And family meals are an ideal place for trying new foods.

But schools can also play an important part. They can teach children about healthy foods, and make it 'real' for them. They can ensure that the foods they serve are healthy and attractive to children.

The nutritional improvements in school meals are great progress, but we need to maintain, and preferably increase, the uptake of school dinners.

The time when children are most open to change is when they are young – it's much harder to persuade a teenager to mend their dietary ways.

This means that primary school – and even younger – is the time to establish good eating habits.

Carina Norris is a Registered Nutritionist.

Teaching children to cook would be more effective

"I'd be concerned until it was clear whether this information was going to be collected anonymously, for policy purposes, or whether children and their parents were going to be told what their BMI (body mass index] is.

"I would oppose it if children were told what their BMIs were and if it became a benchmark for each individual child.

"I'd be very concerned about it, partly because children do compare with each other and it could lead to bullying, and partly because having a numerical measurement doesn't look at the whole person, and doesn't take into consideration issues around weight such as fitness and height.

"Plus, primary age children can't do anything about the lifestyle choices their parents make for them.

"There are also psychological, social and cultural issues about people's relationships with food and health and self-esteem and to load that onto primary age children would be grossly irresponsible and grossly unfair.

"It would be absolutely appalling to tell a child that they didn't fit within a parameter, because if you tell a child they don't fit in it is not only stigmatising but deeply damaging. Also if you do it every year, then what's the yardstick going to be, because children grow so differently?

"I'd be far more interested in the SNP creating working kitchens in every school and introducing cooking from a very young age. If they learned to cook healthily, they could change the habits of a generation by having a practical skil.

"As a parent it is a constant battle against our cultural norms which is that children like chips and sweets, and we have a reward culture around food, where party food is sweets and sweet things.

"That is such a deeply entrenched social culture that measuring is not going to change that.

"The real problem is that children are not getting enough exercise in schools, because there aren't the gym facilities or the time on the timetable.

"Children are coming across BMI in Wii Fit, so clearly they are already talking about it ."

Tina Woolnough is a founder member of Edinburgh-based parent pressure group Parents in Partnership, and has two daughters aged 15 and 13 and a son aged ten.