Long-term time in target range for body mass index (BMI) and diabetes incidence: insights from CHARLS

Abstract

Background: Body mass index (BMI) is strongly associated with the development of type 2 diabetes. However, the association between long-term time in target range (TTR) for BMI and the incidence of new-onset diabetes remains unclear. Methods and results: This study utilized a non-diabetic population aged 45 years or older from the China Health and Retirement Longitudinal Study (CHARLS). BMI-TTR was assessed in Waves 1, 2, and 3 over a 5-year period, with the target range defined as 18.5 kg/m² ≤ BMI < 23 kg/m². New-onset diabetes in Waves 2, 3, and 4 over a 6-year follow-up served as the study endpoint. After applying exclusion criteria, 6662 participants (3143 men and 3519 women; mean age 58.93 ± 8.85 years) were enrolled. Participants were categorized into four groups (TTR1–TTR4) based on the number of times BMI was within the target range (0–3 times). The risk of new-onset diabetes decreased progressively with increasing BMI-TTR during follow-up. Compared with the TTR1 group, participants in the TTR4 group exhibited a significantly lower risk of diabetes (adjusted HR: 0.577, 95% CI: 0.463–0.720, P < 0.001), even after adjusting for baseline BMI (adjusted HR: 0.685, 95% CI: 0.537–0.872, P = 0.002). This effect was even more pronounced in female subgroup and in individuals aged under 60 years of age. Conclusion: In adults aged 45 years or older, regardless of baseline BMI, maintaining BMI within the target range over time was associated with a reduced risk of new-onset diabetes, particularly among women and individuals under 60 years of age. These findings highlight the importance of long-term weight management in diabetes prevention.