[Incidence of increase and decrease in Body Mass Index in middle-aged men and women: four-year follow-up]

The scope of this study was to analyze the incidence of increase and decrease in Body Mass Index (BMI) among middle-aged men and women according to sociodemographic characteristics and classification of nutritional status. It involved a population-based cohort of 689 adults aged 40 to 64 years followed up for four years. The proportion of reduction and increase in BMI (≥1 kg/m²) was verified according to sociodemographic variables and classification of nutritional status in the baseline by means of crude and adjusted Poisson regression. There was a higher incidence of reduced BMI among men in the 55-64 age group (RR: 1.78; 95%CI: 1.06-3.00), in those without a partner (RR: 1.85; 95%CI: 1.09-3.14), in those classified as overweight (RR: 2.06; 95%CI: 1.13-3.74) and in those classified as obese (RR: 2.33; 95%CI: 1.24-4.35), and among women in the 55-64 age group (RR: 1.43; 95%CI: 1.02-2.00) and in those classified as obese (RR: 2.10; 95%CI%: 1.30-3.38). The incidence of increased BMI was lower in the 55 to 64 age group among men (RR: 0.62; 95%CI: 0.41-0.95) and women (RR: 0.68; 95%CI: 0.49-0.95). These data are important for understanding the factors related to the variation of BMI and the elaboration of public policies aimed at the health care of middle-aged adults.