Background Childhood overweight and obesity is a significant national and international public health concern, affecting an increasing proportion of global youth. Despite being framed as a parental problem, several studies suggest that both parents and health care professionals (HCPs) show similar patterns of inaccurate child weight category assignments.

Methods We, therefore, investigated perceptions of child weight status of unselected adults (n= 120; most students), parents (n= 247), and HCPs (n=155). Participants used a visual analogue scale (VAS) to rate the weight status of 3D computer-generated imagery child bodies across the BMI range, and then also categorised the child’s weight status using the National Child Measurement Programme categories (underweight, healthy weight, overweight, and extremely overweight).

Results Results indicated that, overall, all three groups correctly assigned increasingly higher VAS scores to the child bodies as their BMI centiles increased. Although all three groups could accurately distinguish between the different size bodies in the VAS task, participants were much less effective when assigning weight categories to the bodies.

Conclusions From the categorisation patterns we can infer that there was a reluctance to label the child bodies as overweight or extremely overweight. That is, although they perceive the bodies to be getting larger, they are unwilling to assign larger bodies to heavier BMI categories. Although we expected HCPs and parents to distinguish between bodies and assign weight categories more effectively than the ‘naïve’ group, their performance was significantly worse, particularly on categorisation. These findings have important implications, as both parents and HCPs must be able to identify when a child is both underweight and overweight so that they can initiate behaviour change.