The study is observational and single-center and involves (i) the establishment of a retrospective and prospective data collection, and (ii) the development of prognostic and predictive models of response to obesity therapies using statistical modeling and machine learning techniques, exclusively for research purposes.

Data collection will be carried out for each patient diagnosed with obesity or overweight whose first visit to the center occurred from January 1, 2000 up to the start of the study, as well as for patients accessing the center during the subsequent 5 years, including patients who died or were lost to follow-up.

With respect to the primary objective, an interim analysis is planned on the retrospective cohort only, once the collection of data already available at study start has been completed for patients with at least 5 years of follow-up.

Data related to instrumental and laboratory examinations and therapeutic interventions, including pharmacological treatments and group-based educational and behavioral therapies, conducted in accordance with routine clinical practice and the most recent relevant national and international guidelines, will be extracted from the electronic health records routinely used at the study center.

Inclusion Criteria:

• Age ≥ 18 years
• Body mass index (BMI) ≥ 30 kg/m², or BMI ≥ 25 kg/m² with at least one cardiometabolic comorbidity
• Provision of written informed consent

Exclusion Criteria:

• Obesity secondary to hypothalamic-pituitary disorders
• Obesity secondary to adrenal disorders
• Syndromic obesity

The study population will consist of adult patients meeting the study inclusion and exclusion criteria, with a current or past diagnosis of overweight or obesity defined in accordance with the most recent Italian clinical guidelines and the European framework promoted by the European Association for the Study of Obesity (EASO).

Eligible patients will include individuals whose first access to the study site occurred on or after January 1, 2000.