The aim of this study was to evaluate the effect of birth cohort on nutritional status among older elderly (71-81 years old) from the Bambuí Cohort Study of Aging, conducted in Brazil in 1997 and 2008. We compared the two birth cohorts--1916-1926 (older cohort) and 1927-1937 (recent cohort)--considering body mass index (BMI = weight/height²), waist circumference (WC) and prevalence of overweight (BMI ³ 27 kg/m²). BMI (β = 0.09, 95%CI: 0.04, 0.15) and prevalence of overweight (PR = 1.02; 95%CI: 1.01; 1.03) were higher in the recent cohort than the earlier cohort, regardless of sex and schooling. No difference was observed in WC. Stratified by sex, similar overall trends were observed for men, and WC was higher in the recent cohort. Among women there was no difference in BMI and overweight, but WC was lower in the recent cohort. The cohort effect was greater among older men and, in the near future, may result in greater prevalence of overweight in this group.