Perez Cueto Eulert, Armando

Verbeke, Wim

English

Ghent University Academic Bibliography

366Cartas científicasReliability and validity of self-reported weight and height in BelgiumF. J. A. Pérez-Cueto & W. VerbekeGhent University. Department of Agricultural Economics. Ghent. Belgium.Correspondence: F. J. Armando Pérez-Cueto.Postdoctoral Researcher.Ghent University Department of Agricultural Economics.Coupure Links 653, 9000 Ghent, Belgium.E-mail: federico.perezcueto@ugent.beRecibido: 27-I-2009.Aceptado: 11-II-2009.Table ICorrelations and differences between self-reported and measured height and weights in a sample of Belgium adults*All Difference P-value Women Difference P-value Men Difference P-valueVariables Pearson’s between of the Pearson’s between of the Pearson’s between of theCorrelation r means difference Correlation r means difference Correlationr means differenceWeight 1-Weight 2 (in kg) 0,996 -0,04 0,773 0,990 -0,16 0,394 0,996 0,10 0,494Weight 1-Weight measured (in kg) 0,736 -2,76 0,226 0,978 -1,68 < 0,001 0,592 -3,92 < 0,001#Weight 2-Weight measured (in kg) 0,731 -2,72 0,067 0,984 -1,52 < 0,001 0,580 -4,02 < 0,001#Height 1-Height 2 (in cm) 0,997 0,10 0,073 0,989 0,11 0,422 0,997 0,09 0,324Height1-Height measured (in cm) 0,421 1,75 0,044 0,986 0,30 0,148 0,151 3,32 0,143#Height 2-Height measured (in cm) 0,422 1,65 0,089 0,984 0,19 0,213 0,149 3,24 0,142#BMI 1-BMI 2 in kg/m2 0,990 -0,04 0,466 0,987 -0,08 0,274 0,992 0,01 0,842#BMI 1-BMI measured in kg/m2 0,114 -4,16 0,257 0,969 -0,70 < 0,001 0,046 -7,93 0,155#BMI 2-BMI measured in kg/m2 0,102 -4,12 0,262 0,981 -0,61 < 0,001 0,030 -7,94 0,278#* Student’s T-test unless indicated otherwise.# Wilcoxon Signed Ranks Test .The only way to evaluate performance of self-repor-ted anthropometric information is by comparing thosevalues against actual measures. Hence, a small-scalestudy was carried out in Belgium between March andand actual measures of height and weight were asses-sed using Student’s T-test for normally distributedvariables. The non-parametric Wilcoxon Signed RanksTest was used to compare non-normally distributedvariables. All tests were performed with a significancelevel of 0.05.At an aggregated level all variables were normallydistributed, with exception of measured height (P =0.024). When evaluated by respondent’s gender, allwomen’s variables presented normal distribution,including estimated BMI. Men’s self reported heightsand weights were normally distributed; however,Recently some nutrition surveys rely on self-repor-ted weights and heights for the estimation of body-mass-index’ (BMI) based nutritional status, particu-larly when modern online data collection methods areapplied.1 It is still under debate whether such procedu-res are valid or reliable. On the one hand, self-repor-ted height and weight are considered as feasible, use-ful measures in large scale studies,2 while on the otherhand, overestimation of self-reported height andunderestimation of self-reported weight have beendocumented as a sources of individual bias indepen-dently of gender.3April 2008 to assess the reliability and validity of suchvalues. The convenience sample included 71 partici-pants: 37 women (mean age 38 y; SD17) and 34 men(mean age 36 y; SD16). Each respondent had to fill ashort socio-demographic questionnaire and registertheir weights and heights. Three weeks later, they wereasked to repeat the exercise (test-retest reliability).University students weighed and measured each res-pondent according to standard procedures4 to obtaintrue values as reference.Normality of data was assessed with the Kolmogo-rov-Smirnov test. Differences between self-reportedCartas científicas 367Nutr Hosp. 2009;24(3):366-367actual measures and corresponding calculated BMIwere not.Table I shows correlations and differences betweenself-reported and measured heights and weights in thissample. No statistical differences were found betweenself-reported weights and actual measures of weight.The difference between the first self-reported heightand the actual measure was significant for the wholegroup. No statistical differences could be observed bet-ween first and second self-reported values and the con-sequent BMI estimate. For women all correlations bet-ween self-reported and measured values weresignificant, suggesting that females are more reliable inself assessment of height and weight. The oppositeholds for males.The paradoxical message of this study is that in thissample of Belgian adults, self reporting of heights andweights is reliable (respondents provided the samevalues twice) but not valid (inaccurate values) despitehigh correlations with actual measurements. As expec-ted, overweight levels estimated on the basis of self-reported heights and weights would be underestima-ted.5 This limitation should be addressed when repor-ting results based on self-reported anthropometric data.References1. Matthys C, Pynaert I, De Keyzer W, De Henauw S. Validity andreproducibility of an adolescent web-based food frequency ques-tionnaire. J Am Diet Assoc 2007; 107 (4): 605-10.2. Goodman E, Strauss RS. Self-reported height and weight and thedefinition of obesity in epidemiological studies. J Adolesc Health2003; 33 (3): 140-141.3. Danubio ME, Miranda G, Vinciguerra MG, Vecchi E, Rufo F.Comparison of self-reported and measured height and weight:Implications for obesity research among young adults. Econ HumBiol 2008: 6 (1): 181.4. WHO (World Health Organization) Physical Status: the use andinterpretation of anthropometry. World Health OrganizationTechnical Report Series, Editor. 1995: Geneva, pp. 375-411.5. Gorber SC, Tremblay M, Moher D, Gorber B. Diagnostic in obe-sity comorbidities - A comparison of direct vs. self-report measu-res for assessing height, weight and body mass index: a systema-tic review. Obes Rev 2007: 8(4): 307-326.

Reliability and validity of self-reported weight and height in Belgium

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Reliability and validity of self-reported weight and height in Belgium

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