Effect of the type of population on estimates of mean body mass index and prevalence of overweight and obesity: A systematic review of studies of Portuguese adults

Abstract

Background: Prevalence estimates for overweight/obesity vary widely between studies, reflecting true differences across settings and biased sampling.Aim: To compare mean body mass index (BMI) and prevalences of overweight/obesity in samples of different types of population, in Portugal.Methods: A systematic review was conducted to identify studies that assessed the distribution of BMI and overweight/obesity in different populations (general population, blood donors, university students, occupational groups, healthcare users and volunteers). Linear regression was used to quantify age-, sex- and survey year-adjusted differences in these outcomes.Results: When weight/height were measured, BMI was higher among blood donors (1.4 kg/m2) and lower in occupational groups ( - 0.9 kg/m2), compared to the general population. Overweight prevalence was lower among university students ( - 5.2%). Obesity prevalence was higher among occupational groups (4.5%) and healthcare users (8.9%); and lower in volunteers ( - 6.4%). With self-reported data, BMI was lower among university students ( - 0.9 kg/m2), occupational groups ( - 1.2 kg/m2) and volunteers ( - 0.7 kg/m2). Healthcare users had higher overweight (6.7%) and lower obesity prevalences ( - 4.3%) and occupational groups lower obesity prevalence ( - 5.7%).Conclusion: Estimates varied largely across population types. Commonly used solutions for an easier assembling of study samples are likely to yield biased estimates of the distributions in the general population. © Informa UK, Ltd.