[Obesity Discussion]

We designed our method on the observation that numeracy and data handling skills are often taught in schools by getting children to measure their height and weight. We decided to work in partnership with schools to allow us to be part of such a lesson, and to let us use the data anonymously.

We approached all the primary schools in north Birmingham; seven were keen to take part in the project. These included some from the most disadvantaged parts of the Primary Care Trust (PCT) and others from the most affluent.

We arbitrarily chose the year 5 class (aged 9–10) for our pilot. At this age, children are at the threshold between childhood and adolescence. Pragmatically, we felt that it would be the easiest age group to work with, and it would give us a snapshot of the levels of childhood obesity in children before they enter puberty.

We saw the involvement of school nurses as vital. The school nurse for each of the participating schools was invited to take part. All agreed and a meeting was held to tell them more about the project and answer their queries and concerns. It was agreed that, where possible, school health link workers would also attend the lessons to help with measurements.

At a convenient time before the lesson, the school nurse compiled a class list and allocated a number to each child. For each child we recorded date of birth, gender and postal area of residence.

Lesson plan

Working with an educational advisor, we developed a lesson plan suitable for the Key Stage 2 numeracy curriculum (designed for children aged 9–11, see Box 1). This plan was offered to the school, along with a member of healthcare staff (usually the school nurse, plus a link worker) to attend the lesson and help take the measurements thus ensuring consistency of results.

Potential concerns

In developing this method, we had to address two issues of potential concern – parental consent, and the possibility of stigmatization of overweight children.

We obtained parental consent on an 'opt out' basis. We wrote to all parents telling them of the project and explaining our reasons for doing it. We explained that parents could withdraw their child from the lesson by completing and returning a tear-off slip (see Box 2).

Box 1 Lesson outline

The lesson plan is based on the concept of continuous and discontinuous data and how they can be plotted using line graphs and bar charts.

The introduction involves an explanation of the lesson by the teacher and an activity where the children organize themselves into 'living graphs'.

In the main part of the lesson the pupils move in groups between six 'stations' where a variety of measurements and recordings are taken. These include shoe size, eye colour, foot length, hand span and, of course, height and weight. The height and weight stations are manned by healthcare staff. The other recordings and measurements are done by the children themselves.

The data so recorded are used for plotting graphs – either then or in subsequent lessons. Dummy data on height and weight are given to the teacher to use for these purposes so allowing us to keep our measurements private.


Box 2 Parental consent letter

Dear parent

I am writing to tell you about a project that your child's school has agreed to help us with.

As you probably know, there is a lot of worry at the moment about the levels of obesity in our children. We would like to try and find out how serious this problem is in our area, that served by the North Birmingham Primary Care Trust.

We are working with seven schools across this area to run a year 5 lesson during which the children will be weighed and have their height measured.

This will be done in such a way that no child will be made to feel uncomfortable about their size and each child's weight will be kept private. The lesson will be based around number work and graph plotting – there will be no mention of obesity. The weighing and measuring will form only a small part of the lesson, which should be interesting and enjoyable for all.

The school nurse (and probably one or two other healthcare staff) will be present during the lesson, to help with the measuring.

Although we will take away the results these will be anonymous – your child will not be identifiable. We are just looking at numbers – how many children fall into each weight category, not at individuals.

I hope you will be happy for your child to take part in this lesson but if not you may ask for him/her to be withdrawn by completing and returning the slip below.

Finally, if you have a particular concern about your child's height and weight don't forget you may contact the school nurse for advice via the school.



To deal with the potential for stigmatization, we avoided an emphasis on weight. The lesson was specifically designed to be about numbers and graphs rather than health. Weighing was just one of a range of activities during the lesson. We also ensured that each child was weighed separately and the weight kept private from the rest of the class.

The lesson

We explained to the class teacher that the lesson plan was offered merely as a guide. They could freely change the lesson, or use only part of the plan if they wished so long as we had the chance to measure the children in a sensitive way.

One of us (K.R.) and a school nurse attended each lesson. In some cases, an additional link worker was also present.

At the beginning of the lesson, the children were given colourful cardboard wristbands on which was written their personal number (corresponding to the previously complied class list).

The class teacher led the lesson. At some point, the children were divided into groups that went around six 'stations' in turn – these were to measure and record shoe size, hand span, eye colour, foot length and, of course, height and weight. The healthcare staff measured each child's height and weight and recorded it against the number on a pre-prepared results sheet.

Weight was measured, and recorded to the nearest 0.1 kg, using a Salter digital scale, the same set being used in each of the seven lessons. The scales had been calibrated 1 month before the first lesson. The children wore light indoor clothing (shoes and jumper/sweatshirt were removed). Care was taken to keep the weights private – the other children in the group were asked to keep at a distance during weighing. The results sheet was kept covered.

Seca Leicester Portable Height Measures were used to measure height, recording this to the nearest 0.1 cm. The children removed their shoes and were measured in socks.

The healthcare staff in attendance helped the children with their other tasks as required. We felt it was important to be a useful part of the lesson.

The length of the lessons ranged from the usual 1-h numeracy lesson to, in two cases, the whole of the school afternoon (in one of these latter 60 children were measured). In several cases, our weighing and measuring was completed within half an hour and we withdrew quietly as the class teacher began leading the plenary section of the lesson.

At the end of the lesson, the class teacher kept the results sheets for eye colour, shoe size, foot length and hand span. They were given a set of 'dummy' results on height and weight while we took away our real results for these.

Anonymous data on each child's height, weight, age, gender and postal area were recorded and brought away for analysis.

Statistical methods

Each child's height and weight data were converted into a BMI value using the standard formula. We used standard UK BMI reference charts (Child Growth Foundation 1996) to compare the BMI with the reference ranges and to classify each child as normal, overweight and obese using the cut-off percentile points suggested by Cole and colleagues (2000). Further analysis was limited to frequency counts of cases in each category by gender group.

Evaluation

A few weeks after the lesson, we sent out a letter thanking the teachers, together with a questionnaire asking them to evaluate the method. Questionnaires were also sent to the school nurses.