To investigate which anthropometric measure of overweight status, BMI or waist-to-height ratio (WHtR), is most closely associated with parents’ perception of their child's overweight status.

The sensitivity and specificity of parental perception against child-specific BMI and WHtR definitions of overweight were tested.

Primary schools in Queensland, Australia.

Boys and girls aged 9·00–11·99 years (n 1431).

Of the 138 boys and 202 girls who were classified as overweight according to BMI, only 27·5 % (boys) and 22·7 % (girls) were also perceived as overweight by their parents. Using WHtR, 206 boys and 333 girls were classified as overweight, of whom only 21·9 % and 13·8 %, respectively, were perceived as overweight. Perception of overweight was underestimated in approximately 15 % of boys and 21 % of girls when compared with BMI. Underestimation was higher when compared with WHtR: 25 % (boys) and 39 % (girls). Overweight prevalence was significantly lower according to perception than according to BMI or WHtR. Mother's education level was significantly associated with accurate perception of overweight status (P < 0·001).

The sensitivity of parental perception of child overweight was higher when BMI was used. However, emphasis needs to be placed on using WHtR as an actual measure of overweight because high central adiposity is associated with increased risk of CVD. The combined use of WHtR, body-shape images rather than word responses regarding perception and public health messages that educate parents and children about body shape and associated health risks may be the best combination in improving parents’ perception of their child's overweight status.