Age is the most important factor for change in body mass index and waist circumference in older people in southern Brazil.

Objectives: The aim of this study is to assess the changes in body mass index and waist circumference (WC) and their associations with sociodemographic, behavioral, and health characteristics in non-institutionalized older people in southern Brazil over a period of ≤6 y.

Methods: This is a prospective study, with interviews conducted in 2014 and in 2019 to 2020. Of the 1451 individuals from Pelotas, Brazil, aged >60 y and interviewed in 2014, 537 were reevaluated in 2019 to 2020. An increase or decrease was defined as a variation of ≥5% in body mass index and WC in the second visit compared with the first. The association with changes in outcomes was assessed according to sociodemographic, behavioral, and health characteristics using multinomial logistic regression.

Results: Approximately 29% of the older participants lost body mass. Regarding WC, there was an increase in 25.6% in the older participants. The older participants ages ≥80 y had greater odds of losing body mass (odds ratio [OR] = 4.73; 95% confidence interval [CI], 2.29-9.76) and of reducing WC (OR = 2.84; 95% CI, 1.59-6.94). Former smokers had, on average, 41% and 64% lower odds of losing and gaining body mass (95% CI, 0.37-0.95 and 95% CI, 0.19-0.68, respectively), and those who were on ≥5 medications had greater odds of gaining body mass (OR = 1.92; 95% CI, 1.12-3.28) and WC (OR = 1.79; 95% CI, 1.18-2.74).

Conclusions: Despite the high proportion of older people who kept their body mass index and WC stable during this period, many of them lost body mass and gained WC. The findings also highlighted the importance of age in the nutritional changes observed in the population.