The goal of this observational study is to evaluate changes in adipose tissue and skeletal muscle distribution using magnetic resonance imaging (MRI) in adults with obesity undergoing bariatric surgery. The study also aims to investigate the relationship between MRI-derived body composition parameters and metabolic outcomes following surgical treatment of obesity. The main questions it aims to answer are:

How does bariatric surgery affect the distribution of visceral, subcutaneous, hepatic, perirenal adipose tissue and skeletal muscle over 12 months? Are changes in MRI-derived body composition associated with improvements in metabolic parameters after bariatric surgery?

Participants will:

undergo MRI examinations before bariatric surgery and at 1, 6, and 12 months after surgery; undergo routine clinical and metabolic assessments during standard postoperative follow-up; have MRI-derived body composition measurements correlated with metabolic outcomes over the 12-month follow-up period.

Obesity is a chronic metabolic disease associated with increased morbidity and mortality. Beyond body mass index (BMI), the distribution of adipose tissue, particularly visceral adipose tissue, plays a critical role in the development of insulin resistance, type 2 diabetes, cardiovascular disease, and metabolic dysfunction-associated steatotic liver disease. In addition, skeletal muscle quantity and quality are increasingly recognized as important determinants of metabolic health and postoperative recovery.

Magnetic resonance imaging (MRI) is considered the reference standard for non-invasive assessment of body composition, allowing accurate quantification of visceral and subcutaneous adipose tissue, skeletal muscle volume, intramuscular fat infiltration, and ectopic fat depots without exposure to ionizing radiation. Although bariatric surgery has been shown to induce substantial weight loss and improve metabolic outcomes, the temporal changes in regional adipose tissue distribution and skeletal muscle composition remain incompletely understood.

This prospective observational study aims to characterize longitudinal changes in body composition using MRI in patients undergoing bariatric surgery. MRI examinations will be performed before surgery and during postoperative follow-up to evaluate changes in visceral, subcutaneous, hepatic, perirenal, and intramuscular fat, as well as skeletal muscle volume. These imaging findings will be correlated with routinely collected clinical and metabolic parameters to improve understanding of body composition remodeling after bariatric surgery.

The results of this study may contribute to identifying imaging biomarkers associated with metabolic improvement after bariatric surgery and support the development of more personalized strategies for postoperative monitoring and patient management.

Inclusion Criteria:

• Age 18 years or older
• BMI >= 30 kg/m2
• qualified to undergo bariatric surgery
• Ability to provide written informed consent
• Willingness to undergo magnetic resonance imaging before surgery and 3, and 12 months after surgery

Exclusion Criteria:

• Previous bariatric surgery
• Presence of ferromagnetic implants or other contraindications to magnetic resonance imaging
• Previous plastic or surgical procedures affecting the body region assessed by MRI, except cholecystectomy, appendectomy, or inguinal hernia repair
• Chronic kidney disease stage 4 or higher
• Pregnancy
• Claustrophobia preventing MRI examination
• Inability or unwillingness to provide informed consent