Association of the muscle/fat mass ratio with insulin resistance in gestational diabetes mellitus.

This study assessed the association of muscle mass with insulin resistance, evaluated from the insulin sensitivity index (ISI), in Japanese patients with gestational diabetes mellitus (GDM). Consecutive patients with GDM (n = 96) admitted to St. Marianna University Hospital between October 2015 and March 2018 for initial education and glycemic control were enrolled in a prospective observational study. Insulin resistance was evaluated by measuring the ISI and body composition was assessed by bioelectrical impedance analysis. The subjects were aged 34.4 ± 4.8 years (mean ± SD) and their body mass index (BMI) before pregnancy was 22.3 ± 4.0 kg/m2. Fifty-three patients (55.2%) had a history of diabetes in first-degree relatives. The ISI was 7.2 ± 3.3, appendicular skeletal muscle mass (ASM) was 17.0 ± 2.1 kg, and fat mass (FM) was 18.8 ± 8.2 kg. The ASM/FM ratio was 1.02 ± 0.34. There was a positive correlation between FM and ASM (r = 0.734, p < 0.001). To adjust for confounders when evaluating the association of ASM with ISI, multivariate analysis was conducted using age, family history of diabetes, and BMI as variables. In this analysis, the ASM/FM ratio showed a significant positive correlation with ISI (β = 0.303, p = 0.020). These findings suggest that inadequate ASM/FM ratio is important for the development of insulin resistance in Japanese patients with GDM. Excessive emphasis on dieting rather than health might increase the risk of GDM by reducing the muscle mass below the level that maintains normal glucose metabolism.