Judith Gillespie, development manager of the Scottish Parent Teacher Council, has compared East Renfrewshire’s pupil screening programme with an egg-grading process, where only eggs that conform to a certain shape and size are given an A grading.

She said she was particularly concerned about the authority’s strategy of weighing all pupils in S3 - a stage when she said girls were at different stages in their development, with some being at the “naturally lumpy”

stage. Mass weigh-ins could tip some youngsters into eating disorders.

Mrs Gillespie revealed that she had required hospital investigations into her anorexia at a time when very little publicity was given to the illness.

“It was induced by the competition of the weigh-in, eight stone bar. It was a horrendous rubicon that one passed - the attractive girls who were all under it and those over it.”

Mass weigh-ins led to pupils comparing their weight and increased anxiety, she said. “My experience of anorexia is that the only time you get beyond a food obsession is when you do things other than thinking about food.”

But Mary Montague, East Renfrewshire’s education convener, said: “Helping set children on the road to a healthy life is what we aim to do. But to do that, we need to monitor children throughout and obtain consistent and reliable data. That means weighing and measuring pupils at key points in their school careers, and working with them and their families to promote healthy eating and exercise regimes.

Linda Dunion, campaign director of See Me Scotland, an alliance of five mental health associations, said she would be concerned if schools carried out height and weight checks without taking a holistic approach to emotional and mental health at the same time.

However, her experience of schools in East Renfrewshire was that they were proactive in raising awareness of mental health issues. “This could enable schools to pick up on problems that young people may have in terms of eating disorders - if they are below weight, for example.”

She said it would be unfortunate if there was any suggestion that there was an ideal weight below which no one should be.

All Scottish pupils are weighed in P1 as part of a general health check.

The most recent results, in 2004-05, showed that 21.5 per cent of children in P1 were overweight, 9 per cent were obese and 4.4 per cent were severely obese.

Next year, the Scottish Executive will implement new plans to weigh P7 children in a three-year cycle to monitor their long-term health trends.

In East Renfrewshire, all pupils will be weighed and measured at the P1, P4, P7 and S3 stages, in what the council describes as “a drive to fight obesity at one end of the scale and low weight at the other”.

Initial screening by health visitors of pre-school children born in 2001 showed that 19.3 per cent were overweight and 7.4 per cent obese. Figures for P1 pupils screened by the school nursing service show 14.6 per cent overweight and 3.5 per cent obese.

A spokesperson for East Renfrewshire said: “Although the figures are below national averages, education, social work and health chiefs are concerned at the findings.”

“Surprisingly, the results also show that children in East Renfrewshire’s wealthier areas are more likely to be obese, a factor which bucks national trends. Low weight children are most likely to live in parts of Barrhead and Neilston. Anecdotal evidence from schools suggests that more affluent parents tend to give children less healthy snacks and packed lunches.”

Education officials and the community health care partnership which link health and social work in East Renfrewshire have drawn up an action plan.

It includes making all the council’s nursery schools and family centres friendly to breast-feeding mothers to boost good nutrition from birth.

The plan will also encourage nursery schools to work with parents on family cookery courses, aim to increase physical activity for pupils from pre-school right through primary and secondary, and tackle the relatively low 42 per cent uptake of school meals.