Based on three comparable surveys conducted in the last quarter of the 20th century in the most heavily populated areas of Brazil, a substantial change was observed in the secular trend towards obesity based on levels of schooling in the population. While during the first period (1975-1989) there was an increasing risk of obesity for all levels of schooling, with the greatest upward trend for men and women with more schooling, during the second period (1989-1997) the increase in obesity was the greatest for individuals with no schooling, along with a stabilization or even decrease in this condition among groups of females with medium or higher education. As a result of the upward trend, the positive relationship decreased between schooling and risk of obesity in men, and the inverse relationship already observed in the female population was further increased. The main potential implications of these findings are for public health