Non-linear associations of body mass index with impaired fasting glucose, β-cell dysfunction, and insulin resistance in nondiabetic Chinese individuals: a cross-sectional study.

Abstract

Identifying and managing patients with prediabetes is important. The study aims to investigate the association of body mass index (BMI) with impaired fasting glucose (IFG), β-cell dysfunction, and insulin resistance in nondiabetic Chinese individuals. This was a cross-sectional study of consecutive nondiabetic individuals enrolled between January 2014 and January 2015, divided into NFG [normal fasting glucose, fasting blood glucose (FBG) < 5.6 mmol/L) and IFG (n = 450; FBG ≥ 5.6 mmol/L) groups. Restricted cubic splines and piecewise-regression were used to model the association of IFG, impaired b-cell function, and insulin resistance with BMI. Stratified analyses were performed across sex and age. A total of 900 NFG and 450 IFG individuals were enrolled, with a median age of 41 (30-49) years and 1076 males (79.7%). After adjusting for age and sex, the restricted cubic splines showed that the risk of IFG was increasing rapidly until around 27.96 kg/m² of BMI and then started to plateau afterward (p for non-linearity = 0.010), which was similar in males and individuals ≤ 45 years old (p for nonlinearity < 0.001 and = 0.007, respectively). The risk of insulin resistance increased and β-cell dysfunction decreased as the BMI increased in all participants (bothp for non-linearity > 0.05), consistent with the results in males, females, and ≤ 45 and > 45 year olds. The risk of IFG does not rise linearly as the BMI increases, and higher BMI seems to decelerate the rise of the risk.