MUM Kirstie Slay has questioned new childhood obesity figures after health bosses said her three-stone son was overweight.

New NHS figures show of 1,311 reception year children weighed at city schools, 177 are overweight and 111 are obese.

Yet Miss Slay was stunned when figures given for five-year-old son Shawn Birch classed him as overweight.

The Rose Hill resident said Shawn – who is 3ft 5in tall – was a “ball of energy” with a small appetite.

The 25-year-old said: “I was shocked. It’s a struggle to get Shawn to eat as it is.

“He’s constantly moving and playing. I know Shawn barely eats anything but if he did this letter would have seriously made me rethink what I was giving him.”

NHS chiefs hope the national child measurement programme will spur parents into giving their children healthier lifestyles.

Children in reception year, aged four and five, and Year 6, aged 10 and 11, are weighed, though parents can opt out.

Medics calculate a child’s “BMI centile”. A healthy weight is between the second and 90th BMI centile, overweight is 91st to 97th and obese is 98 or over.

A letter from St Michael’s CE Primary School, Marston, asked her to enter his results in an NHS website, which put him as overweight.

The letter from the school placed Shawn at the 90th percentile but the website placed him at the 91st.

Miss Slay questioned whether the BMI ranges were too low and gave parents a false impression of their children’s health. She said: “They are very questionable.”

The latest city figures, for 2010/11, are broadly in line with the previous three years and will raise more concerns about childhood obesity.

Anne-Marie Frohock, a paediatric dietician at the John Radcliffe Hospital , said poor food choices, safety concerns about letting children walk to school and busy parents added to the problem.

She said: “Children are engaged in more sedentary activities outside of school like computer games whereas perhaps, in years gone by, they would be out and about riding bikes and in open spaces.”