Validity of self-reported body weight and height among women including patients with eating disorders.

The main objective of this study was to evaluate the accuracy of self-reported weight and height among women with eating disorders. The study sample consisted of 271 women aged 18-50 yrs: 73 anorexic patients (AN) with a body mass index (BMI) of <18.50 kg/m2, 54 normal weight bulimic or rehabilitated patients (BU/RE: 18.5<BMI<25), 38 overweight/ obese women (OW/OB: BMI> or =25 kg/m2) and 106 normal weight women without an eating disorder (NW: 18.5<BMI<25). Their self-reported body weight (BW) and height were recorded during an interview, and measured using standard procedures, and their self-reported and measured BMI was calculated (kg/m2). In comparison with the measured data, the AN patients tended to overestimate their body weight by 0.48+/-2.05 kg (p<0.05), whereas the OW/OB and BU/RE patients underestimated it (OW/OB: -1.52+/-3.21 kg, p=0.006; BU/RE: -1.12+/-2.60 kg, p=0.003). All of the groups overestimated height by at least 1 cm, and the OW/OB group overestimated it by 2.31+/-2.94 (p=0.00000). These differences were reflected in the significant underestimate of BMI by all groups except the AN patients. Pearson's correlation coefficients between the self-reported and measured variables ranged from 0.95 to 0.98. The results of a Bland & Altman analysis showed that the underestimates of weight and BMI were related to the magnitude of the values (BW: r=-0.24, p<0.000078; BMI: r=-0.37, p<0.00000), the differences being greater with increasing values of weight and BMI; sensitivity as greater for the AN patients. The self-reported data led to a significant misclassification of body mass categories, especially among the BU/RE and OW/OB subjects. Our results show that the over-reporting of height and under-reporting of body weight led to significant underestimates of BMI. The AN subjects seemed to know their weight quite well, whereas the BU/RE and OW/OB women significantly underestimated it. On the basis of these findings, measured weight and height should always be preferred to self-reported values.