Introduction: The American Society of Metabolic and Bariatric Surgery (ASMBS) and the International Federation of Surgery for Obesity (IFSO) have both stated that bariatric surgery (BS) should not be denied in Class I patients. However, lifestyle intervention (LI), such as diet plus gym programs, is still considered the preferred approach for subjects with a BMI ranging from 30 to 35 kg/m2. The aim of this study was to retrospectively compare results of LI and BS in patients in Class I obesity. Methods: Retrospective analysis of prospective maintained databases of two centers for the “Interdisciplinary Treatment of Obesity” was performed. All patients in Class I obesity and follow-up >7 years were included in the study. Subjects were divide...