White adipose tissue (WAT) plays a critical role in whole-body energy homeostasis. In this study, we established the differential proteomic signatures of WAT in glucose-tolerant lean and obese individuals and patients with type 2 diabetes (T2D) and in response to 8 weeks of high intensity interval training (HIIT). We combined a high-throughput and reproducible mass spectrometry-based proteomics pipeline and identified a total of 3773 proteins. We find that a majority of regulated proteins displayed progression from lean to obese and T2D individuals and were highly associated with clinical measures of glucose homeostasis (e.g., insulin sensitivity, HbA1c) and they could, therefore, serve as potential disease biomarkers. Interestingly, HIIT induced a strong increase in WAT ferritin levels independent of group. WAT ferritin levels strongly correlated with individual insulin sensitivity. Thus, we report novel proteomic signatures of WAT related to obesity and T2D and highlight an unrecognized role of human WAT iron metabolism in exercise training adaptations.