The case subjects were obese (BMI ≥35 kg/m2) with a lifetime BMI >40 kg/m2. Independent control subjects were selected who had a current and lifetime BMI ≤25 kg/m2. All the case and control subjects who participated in the current study were part of a previous candidate gene study (13). Sample characteristics are summarized in Table 1 for 430 case and 379 control subjects passing quality control. The median age at obesity onset was 12 years, and 90% had an onset prior to age 26 years. All subjects gave informed consent, and the protocol was approved by the committee on studies involving human beings at the University of Pennsylvania.
