A shift in the epidemiology of low body mass index in Brazilian adults

Objective: To study the prevalence and current predictors of low body mass index (BMI) in a population undergoing a rapid nutritional transition. Design: Population-based cross-sectional study. Settings: Individuals living in the urban area of Pelotas, a medium-sized southern Brazilian city, were interviewed at home. Subjects: A multiple-stage sampling strategy was used. Out of 3372 eligible subjects, 3047 were interviewed. The study was restricted to adults ( >= 20 y). Main outcome measure: Low BMI was defined as <18.5 kg/m(2). Results: The prevalence of low BMI was 2.7% (95% confidence interval: 2.1; 3.3), higher in women than men (3.8 vs 1.3%; P<0.001). In the whole sample ( men and women combined), living without a partner and current smoking were positively associated with low BMI. Among women, low BMI presented a U-shaped relationship with age and was positively associated with educational level. The prevalence of low BMI in young women was 6.3%, and in highly educated young women was 8.9%. Conclusions: Consistently with previous Brazilian studies, a decline in the overall prevalence of low BMI is clear. However, differently from these studies, the predictors of low BMI in women are similar to those observed within developed countries ( including low age and high education), possibly indicating an increase in eating disorders.