Association between body mass index and response to a brief interdisciplinary treatment program in fibromyalgia.

Objective: The aim of this study was to evaluate the association between baseline body mass index (BMI) and treatment outcome after a brief interdisciplinary fibromyalgia treatment program. Design: Subjects (n = 477) with fibromyalgia participated in the fibromyalgia treatment program. They completed the Fibromyalgia Impact Questionnaire (FIQ) and the Short Form-36 Health Status Questionnaire (SF-36) at baseline and 6 to 12 mos after the fibromyalgia treatment program. Posttreatment changes in FIQ and SF-36 scores were compared after stratifying participants into four BMI groups: nonobese, overweight, moderately obese, and severely obese. Results: All BMI groups achieved significant improvement in the FIQ total score; the FIQ subscales feel good, pain, fatigue, and morning tiredness; and the SF-36 subscales pain index, vitality, social functioning, and mental health index. Posttreatment changes in mean scores for each subscale generally did not differ significantly across BMI groups after adjusting for age and baseline scores. However, the SF-36 subscale scores of physical functioning and role-emotional were significantly less improved in the severely obese compared with the nonobese. Conclusions: Baseline BMI did not affect response to the fibromyalgia treatment program, as measured by the FIQ total score or SF-36 physical and mental component summary scores. However, the severely obese group showed less improvement compared with the nonobese group in the SF-36 physical functioning and role-emotional subscales.