Background Given the burden that diabetes and obesity place on patients' quality of life and healthcare systems, elucidating the relationships between diabetes, insulin resistance, and meteorin-like protein may be useful in improving understanding of the pathological processes underlying those clinical conditions. Therefore, this study aimed to evaluate the circulating serum meteorin-like protein levels in patients with obesity and type 2 diabetes mellitus (T2DM) in an attempt to elucidate possible relationships between serum meteorin levels with anthropometric and metabolic parameters of T2DM and obesity. Subjects and methods The study was cross-sectional case-control observational study, carried out in outpatient clinic of Internal Medicine Department, Endocrinology and Metabolism Unit, and Department of Clinical Pathology, Faculty of Medicine, Zagazig University Hospitals from August 2022 to February 2023. This study was carried out on 104 subjects divided into two groups: non-diabetic subjects group and newly diagnosed type 2 diabetic patient group, with futher subdivision according to BMI to obese and non obese subgroup. Results Serum meteorin-like protein levels in newly diagnosed T2DM patients were statistically substantially higher than in nondiabetic controls. Furthermore, when these groups were separated into nonobese and obese subgroups, we discovered that serum meteorin levels were considerably greater in obese nondiabetic controls and obese diabetic patients, than in nonobese nondiabetic controls and nonobese diabetic patients, respectively. Obese T2DM patients had the highest serum meteorin levels …