Obesity as a Risk Factor for Autoimmune Diseases: A Systematic Review and Meta-Analysis

Objective: Obesity is characterized by a proinflammatory condition contributing to poor outcomes, but its association with autoimmunity is inconclusive. To fill this gap in knowledge, we searched PubMed and Embase for studies analyzing the association between obesity and the prevalence and/or incidence of autoimmune diseases. Methods: Adjusted odds ratios (OR) or hazard ratios (HR) with 95% CI relating to the prevalence or incidence of autoimmune diseases in people with BMI > 30, compared to BMI < 25, were pooled using generic inverse variance and fixed effect models. Of 1,311 records, 26 (8 cross-sectional and 18 longitudinal) studies were included in the meta-analysis. Results: Obesity, compared with normal weight, was associated with increased prevalence of rheumatoid arthritis and psoriasis (OR = 1.11 [1.06, 1.16], p < 0.00001; OR = 1.35 [1.14, 1.59], p = 0.0004, respectively) and increased risk of developing rheumatoid arthritis (HR = 1.30 [1.15, 1.49], p < 0.0001), psoriasis (HR = 1.18 [1.16, 1.20], p < 0.00001), multiple sclerosis (HR = 1.49 [1.25, 1.77], p < 0.00001), and Crohn's/ulcerative colitis (HR = 1.35 [1.11, 1.65], p < 0.003). Obesity was also significantly associated with incidence of any autoimmune disease (HR = 1.41 [1.24, 1.62], p < 0.00001). Conclusions: Although definitive conclusions are still precluded for the single diseases, overall evidence supports obesity as a risk factor for autoimmunity.