Microarray gene expression profiling of peripheral blood obtained from obese patients. Blood samples were collected from lean healthy controls (n=20) and from obese patients (n=20) prior to and after initiation of weight loss therapy (patients were later on defined as obese diet-sensitive and obese diet-resistant). Lean subjects (BMI ≤ the 10th percentile for age and sex) and obese patients (body mass index (BMI) = 30-50 kg/m2) were closely matched for age and hormonal status. Patients were excluded on the basis of medical conditions possibly affecting whole-blood gene expression. In this microarray experiment, only samples of obese patients (diet-sensitive and diet-resistant) prior to weight loss therapy were compared to those of lean subjects.