New research suggests parent of obese children often don't recognize that their child is overweight until they have reached extreme obesity levels.

The findings also suggest that parents who are black, south Asian, or from deprived backgrounds are less likely to notice their child's obesity than white parents, the London School of Hygiene and Tropical Medicine reported. Male children's obesity was more likely to go unnoticed than females. These findings could lead to a better evaluation of the efficiency of public health interventions for childhood obesity.

"If parents are unable to accurately classify their own child's weight, they may not be willing or motivated to enact the changes to the child's environment that promote healthy weight maintenance," said Senior author Dr. Sanjay Kinra, Reader in Clinical Epidemiology at the London School of Hygiene & Tropical Medicine and co-lead investigator of the PROMISE trial.

To make their findings the researchers looked at questionnaire responses involving 2,976 children in care trusts taking part in the National Child Measurement Programme (NCMP) ; Redbridge, Islington, West Essex, Bath and North East Somerset and Sandwell.

The research revealed 31 percent of parents involved in the study underestimated their child's Body Mass Index (BMI). Only 4 of the parents described their children as "very overweight" on the scale, even though 369 fell into this classification. The data suggests that for a child with a BMI in the 98th percentile (95th is considered "very overweight") there was an 80 percent change their parents would classify them as being of a healthy weight. Parents whose children were in the 99.7th percentile were more likely to recognize that their child was overweight.

"Measures that decrease the gap between parental perceptions of child weight status and obesity scales used by medical professionals may now be needed in order to help parents better understand the health risks associated with overweight and increase uptake of healthier lifestyles," said co-author Professor Russell Viner, academic pediatrician at the UCL institute of Child Health and PROMISE co-lead investigator.

The findings were published in a recent edition of the British Journal of General Practice.