Angiopoietin-like protein 6 (ANGPTL6) is a circulating protein with a potential role in energy homeostasis. The aim of the study was to explore the changes in ANGPTL6 levels in patients with obesity (Body mass index, BMI > 40 kg/m2) with and without type 2 diabetes mellitus (T2DM) undergoing dietary intervention (very low calorie diet - VLCD) and in a subgroup of T2DM patients after bariatric surgery. Additionally, we examined changes in ANGPTL6 in anorexia nervosa (AN) patients at baseline and after partial realimentation. We also explored the changes in ANGPTL6 mRNA expression in subcutaneous adipose tissue (SAT) of obese subjects.