Association between the change in body mass index from early adulthood to midlife and subsequent type 2 diabetes mellitus

Objective To clarify the quantitative relationship of body mass index (BMI) change from early adulthood to midlife with presence of type 2 diabetes mellitus (T2DM) after midlife. Methods This study included 120,666 middle-aged and elderly, whose retrospectively self-reported body weight at 20 and 40 years and measured height were available. BMI at 20 and 40 years and BMI change in between were defined as early-adulthood BMI, midlife BMI, and early-adulthood BMI change. Results The odds ratio (OR) for T2DM associated with an 1-unit increment of early-adulthood or midlife BMI was 1.08 (95% confidence interval (CI), 1.07-1.08) and 1.09 (95% CI, 1.09-1.10) respectively. In the cross-tabulation of both early-adulthood BMI and BMI change, the prevalence of T2DM increased across both variables. Compared with participants with normal early-adulthood weight and BMI increase/decrease ≤1, the OR (95% CI) for T2DM of participants with early-adulthood overweight/obesity and BMI increase ≥4 kg/m² was 3.49 (3.05-4.00). For participants with early-adulthood underweight and BMI increase/decrease ≤ 1, the OR (95% CI) was 0.85 (0.75-0.97). Subgroup analysis according to sex and age showed similar trends. Conclusions Early-adulthood BMI may influence T2DM prevalence after midlife independent of current BMI. T2DM prevalence after midlife was positively associated with early-adulthood weight gain and inversely related to early-adulthood weight loss, while early-adulthood weight loss could not completely negate the adverse effect of early-adulthood overweight/obesity on diabetes.