Self-reported height and weight and prevalence of obesity. Study in a Spanish population.

The objective of this investigation was to evaluate the usefulness of self-reported measures of height and weight under the hypothesis that they under-estimate the prevalence of obesity. A cross-sectional study was carried out on a random sample of the adult population of the province of León, Spain. The study involved 572 participants (262 men and 310 women). All participants were interviewed and questioned about socio-cultural characteristics plus their weight and height. All respondents were later weighted and measured for height using standard methods. A Quetelet or body mass index (BMI) > or = 30 kg/m2 was used as the index for obesity. Many people were unaware of their weight and/or height. Self-reported BMI could not be calculated in 40 men (15%) and 107 women participants (35%). This occurrence was more frequent in women than in men (chi 2 = 3.98; P < 0.05). The prevalence of obesity, based on measured weight and height, was 1.8 times that from self-reported values in men and 2.5 times that from self-reported values in women. If we consider only the measured values for those individuals who supplied self-reported heights and weights, these prevalences fall to 1.7 and 1.6 times those from self-reported values respectively. In addition, the difference between measured and self-reported height increase with age. All these differences are statistically significant. We believe that the use of self-reported values of weight and height in epidemiological studies should be avoided in an elderly population. These measurements could, however, be used on a younger population.