Sample size is calculated considering bibliographic long term weight loss in both groups, which is 82% in the banded group versus 63% in the not banded group. Thus sample size (n): 67, and adjust by loss sample size: 79 (10% expected loss ratio), not being necessary a 1: 1 ratio between cases and controls and requiring no more than 25 controls, A sample size of 50 cases and 30 controls, total n = 80, will be used.