Background— Obesity is associated with an increased risk of developing microangiopathy, hypertension, and insulin resistance. We hypothesized that obesity is a primary cause of microvascular dysfunction, which may contribute to the development of these obesity-related disorders.

Methods and Results— We examined microvascular function in 16 lean (body mass index <24 kg/m²) and 12 obese (body mass index >30 kg/m²) healthy women (mean age, 38.9±6.7 years) in the basal state and during physiological systemic hyperinsulinemia. We determined skin capillary recruitment after arterial occlusion with capillaroscopy and skin endothelium–(in)dependent vasodilation by iontophoresis of acetylcholine and sodium nitroprusside. Obese women, compared with lean women, had higher systolic blood pressure (P<0.05), impaired insulin sensitivity (P<0.01), impaired capillary recruitment in the basal state (P<0.05) and during hyperinsulinemia (P<0.05), and impaired acetylcholine-mediated vasodilation in the basal state (P<0.05) and during hyperinsulinemia (P<0.01). Sodium nitroprusside–mediated vasodilation was similar in lean and obese women. Capillary recruitment and acetylcholine-mediated vasodilation were positively correlated with insulin sensitivity (r=0.58, P<0.01 and r=0.55, P<0.01, respectively) and negatively with blood pressure (r=−0.64, P<0.001 and r=−0.42, P<0.05, respectively) in both lean and obese women.

Conclusions— Obesity is characterized by impaired microvascular function in the basal state and during hyperinsulinemia and, in both lean and obese women, microvascular dysfunction is associated with increased blood pressure and decreased insulin sensitivity. These findings are consistent with a contribution of impaired microvascular function to the development of obesity-related microangiopathy, hypertension, and insulin resistance.