RESUMO

The purpose of the present study was to measure body composition in a probability sample of adults (≥ 20 years) living in Niterói, State of Rio de Janeiro, Brazil, and to assess the adequacy of the World Health Organization (WHO) recommended body mass index (BMI) cut-offs values for identifying obesity in this population. Anthropometric measures and percentage body fat (%BF) assessments were taken with 550 fasted individuals (352 women). Obesity was classified according to the WHO recommended BMI cut-off values. %BF predictive equations were developed based on the inverse of BMI. BMI and %BF mean values (standard error) were: 25.3 kg/m(2) (0.3) and 38% (0.4) for women and 25.1 kg/m(2) (0.3) and 22.1% (0.6) for men. The predicted %BF values (regression of %BF on the inverse of BMI) for each BMI cut-offs of 18.5, 25 and 30 kg/m(2) were: 26.3%, 38.6% and 44.5% for women and 5.6%, 23.2% and 31.5% for men, respectively. The BMI values for the %BF-estimated obesity cut-off values were 20.5 for men and 25.7 kg/m(2) for women. Based on the BMI-%BF relationship, the BMI cut-off values recommended by the WHO are not adequate in identifying obesity in adults from this population.

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RESUMO

The purpose of the present study was to measure body composition in a probability sample of adults (≥ 20 years) living in Niterói, State of Rio de Janeiro, Brazil, and to assess the adequacy of the World Health Organization (WHO) recommended body mass index (BMI) cut-offs values for identifying obesity in this population. Anthropometric measures and percentage body fat (%BF) assessments were taken with 550 fasted individuals (352 women). Obesity was classified according to the WHO recommended BMI cut-off values. %BF predictive equations were developed based on the inverse of BMI. BMI and %BF mean values (standard error) were: 25.3kg/m² (0.3) and 38% (0.4) for women and 25.1kg/m² (0.3) and 22.1% (0.6) for men. The predicted %BF values (regression of %BF on the inverse of BMI) for each BMI cut-offs of 18.5, 25 and 30kg/m² were: 26.3%, 38.6% and 44.5% for women and 5.6%, 23.2% and 31.5% for men, respectively. The BMI values for the %BF-estimated obesity cut-off values were 20.5 for men and 25.7kg/m² for women. Based on the BMI-%BF relationship, the BMI cut-off values recommended by the WHO are not adequate in identifying obesity in adults from this population.

O presente estudo mediu a composição corporal em uma amostra probabilística de adultos (≥ 20 anos) de Niterói, Rio de Janeiro, Brasil, e avaliou a adequação dos pontos de corte do índice de massa corporal (IMC) da Organização Mundial da Saúde (OMS) para obesidade nessa população. Medidas antropométricas e de percentual de gordura corporal (%GC) por impedância bioelétrica foram obtidas em 550 (352 mulheres) adultos em jejum. A obesidade foi diagnosticada segundo os pontos de corte de IMC da OMS. Equações de predição para %GC em função do inverso do IMC foram desenvolvidas. Os valores médios (erro padrão) de IMC e %GC foram: 25,3kg/m² (0,3) e 38% (0,4) para mulheres e 25,1kg/m² (0,3) e 22,1% (0,6) para os homens. Os valores preditos de %GC para IMC de 18,5, 25 e 30kg/m² foram: 26,3%, 38,6% e 44,5% para as mulheres e 5,6%, 23,2% e 31,5% para os homens, respectivamente. Os valores de IMC para os pontos de corte para a obesidade baseados no %GC foram 20,5 (homens) e 25,7kg/m² (mulheres). Baseado na relação IMC-%GC, os pontos de corte de IMC propostos pela OMS não são adequados para identificar obesidade em adultos de Niterói.

El presente estudio midió la composición corporal en una muestra probabilística de adultos (≥ 20 años) de Niterói, Río de Janeiro, Brasil, y evaluó la adecuación de los puntos de corte del índice de masa corporal (IMC) de la Organización Mundial de la Salud (OMS) para la obesidad en esta población. Las medidas antropométricas y de porcentaje de grasa corporal (%GC) por impedancia bioeléctrica se obtuvieron de 550 (352 mujeres) adultos en ayunas. La obesidad fue diagnosticada según los puntos de corte de IMC de la OMS. Se desarrollaron ecuaciones de predicción para %GC en función del inverso del IMC. Los valores medios (error patrón) de IMC y %GC fueron: 25,3kg/m² (0,3) y 38% (0,4) para mujeres y 25,1kg/m² (0,3) y 22,1% (0,6) para los hombres. Los valores previstos de %GC para IMC de 18,5, 25 y 30kg/m² fueron: 26,3%, 38,6% y 44,5% para las mujeres y 5,6%, 23,2% y 31,5% para los hombres, respectivamente. Los valores de IMC en los puntos de corte para obesidad basados en el %GC fueron 20,5 (hombres) y 25,7kg/m² (mujeres). Basado en la relación IMC-%GC, los puntos de corte de IMC - propuestos por la OMS - no son adecuados para identificar obesidad en adultos de Niterói.

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BACKGROUND & AIMS: Metabolic carts used in laboratory settings for the measurement of resting metabolism are cumbersome limiting their use in the field. The validity of a newly developed portable calorimeter (Medical Graphics VO2000) under resting conditions was assessed in comparison to a well-established reference system, the DELTATRAC. METHODS: Gas exchange and energy expenditure were measured for 25 min consecutively using the two devices. Values of the last 20 min were averaged and used in the analysis. The order of device for the first subject was randomly chosen and the calorimeters were alternated thereafter. RESULTS: Among 33 subjects, acceptable measures of resting metabolism were obtained in 25 (11 men) aged 20-78 years because eight subjects (three men) either hyperventilated or did not adapt well enough to the facemask. VO(2), VCO(2), and RQ were not significantly different between devices. Small (2.8%) non-clinically relevant mean differences (-0.145+/-0.341 MJ day(-1)) were found. Results of the two devices were highly correlated (r=0.95) yielding a more accurate estimate than predictive equations. CONCLUSIONS: The VO2000 calorimeter is a valid system to measure resting metabolism but the facemask may not be suitable for some people.

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