Obesity in 16-year-olds assessed by relative weight and doctors' rating

Weights and heights at age 16 of 5652 boys and 5280 girls from the National Child Development Study (NCDS) were measured. At this examination, school medical officers rated the boys and girls into one of the following categories: grossly obese, moderately obese, normal, thin or very thin. A comparison is made between doctors' rating and assessment of obesity by relative weight (RW). Obesity was defined as RW greater than 120. Overall 803 (15.2 per cent) girls were rated obese by doctors compared with 469 (8.9 per cent) identified by RW. Only 414 (7.8 per cent) girls were considered obese by both methods. In boys the difference between the two methods was less marked. There were 362 (6.4 per cent) boys rated as obese by doctors, 404 (7.2 per cent) by relative weight and 262 (4.6 per cent) by both methods. The discrepancies demonstrate that one method of assessment cannot replace another. Doctors' rated considerably more girls than boys as obese. Although at this age girls were heavier than boys for a given height, the doctors' rating may also reflect the different attitudes towards obesity in men and women which are prevalent in our society. Without comparison with a more accurate measure of adiposity it is not possible to reach a definite conclusion as to whether clinical assessment, relative weight, or indeed both methods combined are the most suitable for identifying obese adolescents.