More Oxfordshire children are obese, according to new figures.

The Government’s child weight measurement scheme shows there has been a reduction in the number of underweight children and an increase in both overweight and obese children aged four to 11 in the county.

According to NHS Oxfordshire, the primary care trust, one in five children in Oxfordshire start school either overweight or obese.

In addition, one in three are classed as overweight or obese by the time they leave primary school in year six.

Every year, children in reception year, aged from four, and year six, aged from 10, are weighed and measured as part of the National Child Measurement Programme.

Their results are then calculated individually to work out their Body Mass Index (BMI), to see what their body fat percentage is.

This varies according to each child, but a healthy BMI usually falls between 20 to 25 per cent body fat.

The results are analysed to see if they fall within a “healthy range” and are sent in a report to parents along with additional healthy eating and lifestyle information.

When the weight measurement scheme started in 2006, 12.2 per cent of reception pupils were classed as overweight and eight per cent were classed as obese.

The figures for 2009 show the percentage of overweight four- to five-year-olds has risen to 14.6 per cent.

The number of those who are classed as obese has increased to 8.7 per cent.

In year six, the percentage of overweight children jumped from 13 per cent to 14.2 per cent, while the percentage of obese children rose from 15.4 to 16 per cent, making one in three children in year six either overweight or obese.

NHS Oxfordshire says initial studies show west Oxfordshire has a much higher percentage of children who are overweight in the reception year than the rest of the county, but they do not know why.

Donna Husband, health improvement practitioner for the PCT, said: “We are treating these initial results with caution.

“We need to understand why these results are so much higher in the west.

“This could be for a number of reasons. Parents should be reassured that we are looking into this.”

Ms Husband said that apart from low levels of fitness, overweight children could also suffer low self-esteem, social discrimination and bullying.

She added: “Obese children are more likely to become obese adults, making them more vulnerable to serious conditions that increase the risk of heart disease, stroke, diabetes, high blood pressure and some cancers.

“The younger the child is when they become overweight or obese the longer the likelihood that they will live with a long-term health problem.”