Additional Study Information: This study is designed to determine the role of specific genes in obesity and/or type 2 diabetes mellitus. Patients who are severely obese, and/or with an onset of type 2 diabetes at less than 25 years of age. Ideally, we would like to have families involved in this study. The ideal family is one in which NOT everyone in the family is obese or diabetic. Families in which one or neither parent is obese/diabetic, and some but not all children are obese/diabetic, are ideal.