The objective of this randomized clinical trial is to compare pain levels during and after insufflation with carbon dioxide or in subjects that will undergo endoscopic fulguration with argon to reduce the diameter of the gastrojejunal anastomosis. The investigators hypothesize that carbon dioxide will be superior in causing less pain and leading to less discomfort.

Laparoscopic gastric bypass surgery is one of the strategies oriented towards weight reduction in obese patients. Although in the short term it has a high degree of success, weight regain is common in the long term, in part due to the dilatation of the anastomosis that allows food to pass without barriers and hinders the purpose of bypass surgery. Fulguration with argon is an endoscopic technique that reduces the diameter of the anastomosis, offering resistance to food passage and improving patient outcomes.

Although carbon dioxide is the current standard for laparoscopic surgery, its use for fulguration with argon as compared to ambient air has not been investigated in the setting of the stenosis of a dilated anastomosis following gastric bypass surgery. stenosis. Therefore, to investigate pain during and after this procedure, investigators will conduct a randomized clinical trial comparing carbon dioxide and ambient air.

The secondary aims will be to measure the diameter of the gastrojejunal anastomosis during three endoscopic sessions and in a final control examination eight weeks after the third session; to determine whether the patient loses weight or not by the final control objective after three sessions of endoscopic fulguration with argon; to analyze if the method employed is able to reduce body weight to the minimum weight achieved after bariatric surgery;and to investigate whether there is a correlation between the percentage reduction in anastomotic diameter and the percentage loss of regained weight.

Inclusion Criteria:

• Regain of at least 10.0% of the minimum weight reached after the gastric bypass;
• Ability to understand study procedures;
• Signed the informed written consent form;
• Possible to complete all the stages of the study.

Exclusion Criteria:

• Presence of very tight restrictive ring preventing the advancement of the endoscopy device;
• Stenosis of the anastomosis preventing the progression of the endoscopy device before the end of the three endoscopic sessions;
• History of liver diseases such as cirrhosis or chronic active hepatitis;
• Patients who required anticoagulant therapy with the exception of antiplatelet agents;
• Pregnant women or those intending to become pregnant within 12 months after fulguration with argon;
• Participant in another ongoing clinical research;
• Recent history of neoplasia (less than 5 years);
• Alcoholism or drug use;
• HIV positive;
• Unbalanced or uncontrollable psychiatric disorders;
• Anemia or severe nutritional deficiencies;
• Allergy to anesthetic compounds;
• Impossibility to return within defined periods for consultations and endoscopic sessions of fulguration with argon;
• Inability to follow nutritional guidelines after each endoscopic session;
• Inability to understand study procedures;

Both the participant and the outcome assessor will be blinded to the study intervention.