The aims of this study were: (i) to estimate the dependency between BMI and waist:height ratio (WHtR) as measures of general and abdominal adiposity, and (ii) to evaluate the influence of socio-demographic factors on both measures and on their dependency in risk classification. Data from a cross-sectional study conducted in 2009 among a representative sample of 3529 Portuguese adults were used. Height, weight and waist were measured and socio-demographic data (sex, age, education level, occupational status, marital status, region of residence) were obtained. Using logistic regression, crude and adjusted OR for high general (BMI≥25·0 kg/m²) and abdominal (WHtR≥0·5) adiposity, and for incompatible classification between them, were calculated. Above half (50·8%) of the respondents had high BMI and 42·1% had high WHtR, and the rates were higher in men than in women. There was an inverse association between education level and both adiposity measures. The lowest prevalence of high general and abdominal adiposity was observed in students and singles, whereas the highest was found in retired, widowed and respondents from Azores, Madeira and Alentejo. Nearly a quarter of respondents (24·0%) were incompatibly classified by BMI and WHtR, with higher prevalence in men than in women and in low- than in high-educated people. Future surveys should focus on developing at least sex-specific cut-offs for both measures. Implementation of effective strategies for preventing and reducing high adiposity levels in Portugal should be directed primarily to men, older, low-educated individuals, as well as those living in the islands and poor regions of the country.
Keywords: Abdominal adiposity; BMI; Obesity; SES socio-economic status; Socio-demographic factors; WC waist circumference; WHtR waist:height ratio; Waist:height ratio.