INS and obesity due to melanocortin 4 receptor deficiency: As reported previously, this autonomic dysfunction is probably linked with environmental factors, such as a sedentary lifestyle and development of type 2 diabetes.18,30 We speculate that obesity itself may have a strong effect on the insulin response and may increase insulin levels regardless of HRV function.35 Therefore, the effect of HRV may become more evident in non-overweight individuals.