Adipocyte volume has been associated with insulin resistance and type 2 diabetes.

Our purpose was to identify an adipocyte volume threshold linked with increased insulin resistance risk, and to examine its association with insulin resistance improvement after bariatric surgery.

We investigated two cohorts of Caucasian women, candidates for bariatric surgery, from two institutional centers in France (age 42.0 ± 11.5 years; body mass index, 47.6 ± 6.9 kg/m²) and Germany (age 41.3 ± 11.2 years; body mass index, 49.5 ± 8.1 kg/m²). 38% of the subjects had gastric bypass surgery and were followed for 6 months after the intervention. We defined a group of subjects with type 2 diabetes or at risk of type 2 diabetes (DRD) and investigated the relations between adipocyte volume and this status before and after surgery.

In both cohorts, subjects with DRD presented enlarged adipocytes (France, P = 3×10⁻⁴; Germany, P =3×10⁻¹⁰) and we were able to determine thresholds in each cohort above which diabetes risk was potentially increased (France: 1003±42 pL, Germany: 798±32 pL). Subjects above those adipocyte thresholds were less prone to disappearance of the DRD status after bypass surgery (France, risk ratio = 2.1, P = .024; Germany, risk ratio = 1.3, P = .05).

We show in two cohorts of morbidly obese subjects that a specific adipocyte volume threshold may predict an increased risk for obesity-associated type 2 diabetes. However, this threshold might be established for each specific investigation site. Having a high adipocyte size is associated with a lower improvement of insulin resistance after bypass surgery in both cohorts.