This study focused on adult obesity prevalence in Goiânia, Goiás State, Brazil, and the association between socio-demographic variables, lifestyle, physical activity, eating habits, and food consumption frequency and body mass index (BMI). A cross-sectional study was conducted in 2001 with a sample of 1,252 individuals from 20 to 64 years of age. The association between socio-demographic variables, lifestyle, food consumption, and physical activity and BMI was evaluated by hierarchical multiple linear regression analysis. Obesity prevalence was 10.7% in men and 13.9% in women. In males, age, income, and meat consumption showed a positive association with BMI, while physical activity during leisure time and commuting and the habit of eating > 4 meals per day were inversely associated with BMI. In women, positively associated factors were age, no smoking, and no meat consumption; in contrast, consumption of grains was inversely associated with BMI. High obesity prevalence was observed; active lifestyle coupled with ingestion of more grains and less meat appeared to protect against increased BMI.