The 2nd study is based on a clinical setting and aims to recruit 100 morbidly obese subjects undergoing VSG to compare their BA and metabolic profiles pre- to 1 year post-surgery. This study is based on observations that post-VSG BA synthesis is increased, but changes in BA composition towards possibly harmful profiles have not previously been studied. It is also hypothesized that the degree of weight loss and metabolic improvement in VSG patients may be related to pre-surgical BA profiles.