This study from 2016 shows a fairly definite correlation (which does not mean causality) between inconsistent sleep schedule and increased insulin resistance:
“After adjustment for race, menopausal symptoms, sleep duration, exercise, depressive symptoms and BMI, positive associations were found between homeostasis model of assessment for insulin resistance (HOMA-IR) and variability in bedtime (P = .007) and bedtime delay (P = .013). Before adjustment, higher HOMA-IR was associated with greater bedtime advance (P = .05). No relationship was found between HOMA-IR and mean bedtime. Higher BMI was linked to greater bedtime advance (P = .047).”