The number of children suffering from obesity could be greater than official figures show, research has revealed.

Data based on Body Mass Index (BMI) measurements may not show the true extent of the current childhood obesity epidemic, according to a study by Leeds Metropolitan University.

Hundreds of children, who were not classed as being obese using BMI alone, were found to be overweight when experts looked at their waist measurements.

Nearly 15,000 children at schools in Leeds took part in the three-year study comparing BMI, waist circumference and waist-to-height ratio.

The results, published in the Obesity journal, found 429 boys (6 per cent) and 992 girls (15 per cent) were classed as overweight or obese who would not have been identified based on BMI measurement alone.

More than 2,000 11-year-old girls exceeded a waist measurement of 31.5in (80cm) - the point at which women have an increased risk of developing Type 2 diabetes.

Experts said recent research showing a link between waist circumference and the risk of Type 2 diabetes meant the results of the study were a concern.

Claire Griffiths, a senior lecturer who led the study, said: "Although the choice of BMI as a measure of obesity in children is well-established, and even recommended, widespread use of BMI to assess fatness in children may conceal differences in body composition and central adiposity which potentially pose a greater health risk.

"Conclusions linking BMI, waist circumference and waist-to-height ratio as measures of obesity to health risk in children cannot be drawn from the data. However, the data could have serious implications for public health, suggesting that there is a need to understand the relationship between BMI and waist circumference, with growth and health risk."

The study of 14,697 children was conducted with childhood obesity expert Professor Paul Gately, Dr Paul Marchant and Professor Carlton Cooke in collaboration with Leeds City Council.