The study discovered that parents were more likely to underestimate their child’s weight if they were black or south Asian, from more deprived backgrounds or if the child was male.
According to the research, published in the British Journal of General Practice, just under a third (31 per cent) of the parents who took part in the study underestimated their child’s body mass index (BMI) on obesity scales, which classify children as very overweight (or obese), overweight, healthy weight, or underweight.
Just four parents described their child as being very overweight despite 369 children being identified as such.
According to official guidelines, children are classified as overweight at the 85th centile and obese at the 95th centile.
The team estimated that for a child with a BMI at the 98th centile there was an 80 per cent chance that the parent would classify their child as a healthy weight.
Researchers suggested that if parents cannot identify when their child is overweight, it leads to questions about the effectiveness of public health interventions aimed at addressing obesity in the home. A third of children in England are now classed as overweight or obese.
Senior author Dr Sanjay Kinra, reader in clinical epidemiology at the London School of Hygiene & Tropical Medicine, said: “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.”
Co-author Professor Russell Viner, academic paediatrician at the UCL institute of Child Health, added: “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.”