Design and rationale of the Utah obesity study. A study to assess morbidity following gastric bypass surgery.

PURPOSE: This paper details the design and baseline characteristics of a study on the morbidity associated with Roux-en-Y gastric bypass surgery (GBP) in severely obese adults. This study is designed to assess the effectiveness of GBP in reducing morbidity and maintaining weight loss. A wide array of clinical tests and psycho-behavioral questionnaires are included as part of the study.
METHODS: Three groups (n=1156 severely obese) have been recruited for this study: cases who were approved for and participated in surgery (n=415), a control group of GBP seeking individuals who were denied surgery (n=420) and a control group that was randomly chosen from a population of severely obese participants who were not seeking GBP (n=321). Clinical measures include: a physician interview and detailed medical history, resting electro- and echocardiograms, a submaximal exercise treadmill test and electrocardiogram, pulmonary function, limited polysomnography, resting metabolic rate, anthropometrics, resting and exercise blood pressure, comprehensive blood chemistry and urinalysis and dietary, quality of life and physical activity questionnaires. Most participants (76%) were tested following an overnight stay in a clinical research center. Remaining participants underwent less extensive testing in an outpatient clinic.
RESULTS: Baseline characteristics of the 1156 participants are available for selected measures. Mean+/-S.D. for BMI was 46+/-7.5 kg/m(2) (range=33 to 92) and for age was 44+/-11.4 years (range=18 to 72). The prevalence of diabetes and hypertension was 19% and 35%, respectively. Of the participants who had an echocardiogram or polysomnogram, 92% had left-ventricular hypertrophy and 85% had mild to severe sleep apnea. The two control groups were similar to the surgical group. At approximately 24 months, all participants will have a second clinical examination. Statistical comparisons of changes in morbidity variables will be made between the surgical and control groups.
CONCLUSIONS: This study design facilitates assessment of risks and benefits of GBP to perform recommendations on whether or not to perform surgery on the severely obese patient. Baseline and 2-year exams provide valuable data for comparison to future long-term follow-up data that can be collected at 5 and 10 years.