Estimates of obesity based on self-report versus direct measures.
OBJECTIVE
Based on a representative sample of the Canadian population, this article quantifies the bias resulting from the use of self-reported rather than directly measured height, weight and body mass index (BMI).


METHODS
The analysis is based on 4,567 respondents to the 2005 Canadian Community Health Survey (CCHS) who, during a face-to-face interview, provided self-reported values for height and weight and were then measured by trained interviewers.


RESULTS
On average, males over-reported their height by 1 cm, and females, by 0.5 cm. Females under-reported their weight by an average of 2.5 kg; males, by 1.8 kg. Reporting bias in weight was strongly associated with measured BMI category. Under-reporting of weight was high among people who were overweight, and particularly high among those who were obese, compared with people of normal weight. When based on measured rather than on self-reported values, the prevalence of obesity was 9 percentage points higher among males and 6 points higher among females.
Shields
Margot
M
Health Information and Research Division, Statistics Canada, Ottawa, Ontario, Canada. Margot.Shields@statcan.ca
Connor Gorber
Sarah
S
Tremblay
Mark S
MS
D000293:Adolescent; D000328:Adult; D000368:Aged; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002170:Canada / Q000453:epidemiology; D002648:Child; D005260:Female; D006306:Health Surveys; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000453:epidemiology*; D015995:Prevalence; D012650:Self Disclosure; D012680:Sensitivity and Specificity; D012959:Socioeconomic Factors