The aim of the present study was to assess the body composition in an adult Mediterranean population by two methods, to identify groups at risk for obesity and lifestyle factors that might influence this risk. A cross-sectional study was carried out in Andalusia, a western Mediterranean region in southern Spain. Body composition was studied with anthropometric methods and bioelectric impedance analysis (BIA) in a random sample of 394 subjects (169 men, 225 women) between 20 and 60 years of age. When anthropometric methods were used, we found that 19.4% of the individuals had a body mass index (BMI) > or = 30 kg/m(2). In 46.2% of the men, more than 25% of the body weight consisted of fat, and in 74.1% of the women, more than 30% of the body weight consisted of fat. When BIA data were used, these values rose to 34.7% and 60.6% for men and women respectively. After controlling for sex, age correlated directly with percentage of body fat when skinfold thickness (r = 0.58) or BIA (r = 0.40) was used. In smokers, the number of cigarettes/day correlated directly with waist circumference (r = 0.76), after controlling for both age and sex. We found high percentages of obesity regardless of the indicator or method used, particularly in women. Factors such as sex, age, leisure-time physical exercise, educational level, and smoking appeared to influence obesity. The factors that made the greatest contribution to the rates of obesity and high waist-hip ratio were the age, time spent exercising, and educational level. In contrast, the risk of high body fat (as determined with both methods) was associated only with sex and age.