OBJECTIVE: The aim of this study was to examine the impact of an increased body mass index (BMI) on disease activity, damage accrual, fatigue, self-reported health-related quality of life (HRQOL), and fibromyalgia in patients with lupus using longitudinal data from LUMINA, a large multiethnic cohort. METHODS: SLE patients (≥4 ACR revised criteria), ≤5 years disease duration at entry into the cohort (T0), of Hispanic (from Texas or from the Island of Puerto Rico), African American, or white ethnicity were included. BMI was ascertained at T0 or first recorded. The average scores from all visits for disease activity (SLAM-R), self-reported HRQOL (physical and mental component summary measures of the SF-36) and fatigue (Fatigue Severity Scale), the score at last visit for damage accrual (SLICC Damage Index), and fibromyalgia (ACR criteria), if present at any visit, were examined for their association with an increased BMI by univariable and multivariable analyses. RESULTS: Three-hundred sixty-four patients were included; 28% were obese (BMI ≥30 kg/m). An increased BMI was associated with older age, less social support, higher degree of helplessness, depression, more abnormal illness-related behaviors, poorer self-reported HRQOL, fatigue, and fibromyalgia, but not with disease activity or damage accrual by univariable analyses. In multivariable analyses, BMI was independently associated with fibromyalgia but not with disease activity, fatigue, or self-reported HRQOL. CONCLUSIONS: An increased BMI is independently associated with presence of fibromyalgia but not with disease activity, damage accrual, fatigue or self-reported quality of life in patients with SLE. Optimizing weight merits investigation to see if it can significantly impact this pervasive SLE-associated manifestation. © 2007 Lippincott Williams & Wilkins, Inc.