TITLE: Randomized study conducted in a single center, with the aim of comparing the three main filling volumes of the intragastric balloon in overweight or obese patients (BMI \>27 and \<60 kg/m2). OBJECTIVE: To establish the efficacy and safety of the intragastric balloon inflated to different volumes in patients who are candidates for balloon placement for overweight or obesity. To date there is no well-defined filling volume and each Endoscopist inflates the balloon to a random volume between 500 and 700 ml according to the experience acquired, but without a clear rationale. DESIGN: All overweight or obese patients with an indication for intragastric balloon placement will be preliminarily examined by a multidisciplinary team composed of a gastroeterologist, surgeon, nutritionist, psychologist, radiologist and endocrinologist. Before each bariatric procedure, patients will undergo a psychometric and nutritional evaluation in order to identify any psychopathological conditions that contraindicate the operation. The enrolled patients will be randomly divided to be candidates for balloon placement: * 1/3 of patients will undergo treatment with an intragastric balloon inflated with 500 ml of saline solution and methylene blue, a space-occupying technique, which will be left in place for 1 year; * 1/3 of patients will undergo treatment with an intragastric balloon inflated with 600 ml of saline solution and methylene blue; * 1/3 of patients will undergo treatment with an intragastric balloon inflated with 700 ml of saline solution and methylene blue. All balloons will remain in place for 6 months, as per the instructions provided in the product technical data sheet. All the techniques described have already been widely validated by the scientific literature and are commonly used in bariatric endoscopy. Sample size: assuming a significant level of 0.05, to detect as significant a medium effect size (f=0.25) with a power of 80% performing an ANOVA model we will need to enrol 156 patients (52 in each group). Taking into account a possible 5% of drop-out at the enrollment, the total number of patients will be around 165 (55 per group). INFORMED CONSENT: Will be obtained upon first registration of the patient in the computer archive, as required by the hospital computer system, for access to personal data, which will be then used anonymously.