BACKGROUND: Multiple sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system. It is characterized by inflammation, demyelination, and destruction of the axons. Obesity is a worldwide health issue that involves excessive accumulation of body fat, resulting in negative metabolic and health effects. The association between MS and obesity has received more attention in recent years. OBJECTIVES: The current study aims to evaluate the relationship between MS and obesity and determine whether obesity is a risk factor for MS development, relapse, and disability. METHODS: A case-control study was conducted at the Basrah Teaching Hospital MS clinic to compare 80 MS cases with 100 healthy controls, who were age- and sex-matched. Data collected from 1/6/2023 to 1/1/2024 includes sociodemographic factors, clinical characteristics, anthropometric measures, family and childhood obesity history, relapse frequency, and expanded disability status scale scores (EDSS). RESULTS: The study compared 80 MS cases with 100 controls. While mean age differed slightly between MS cases (32.34 ± 9.28 years) and controls (30.58 ± 8.67 years), it was not significant (P = 0.196). Female predominance was noted in MS cases (66.3%, n = 53) versus controls (54.0%, n = 54), with no significant difference (P = 0.126). Among the MS cases, the majority exhibit relapsing-remitting MS (RRMS) (73.7%, n = 59), followed by primary progressive MS (PPMS) (16.2%, n = 13), clinically isolated syndrome (CIS) (6.3%, n = 5), and secondary progressive MS (SPMS) (3.8%, n = 3). Childhood obesity was significantly associated with MS development (26.3%, n = 21 in MS cases vs. 1.0%, n = 1 in controls, P = 0.001). Body mass index (BMI) was significantly higher in MS cases (25.04 ± 3.61) than in controls (24.75 ± 3.37, P = 0.016), with a higher proportion of obesity (15.0%, n = 12 in MS cases vs. 5.0%, n = 5 in controls, P = 0.027). A moderate positive correlation existed between BMI and both relapse frequency (r = 0.610) and EDSS scores (r = 0.454), both statistically significant (P = 0.001). CONCLUSIONS: The study found a significant association between increased BMI and MS occurrence, with strong associations to relapse frequency and EDSS scores. Childhood obesity was also linked to MS development, but not a family history of obesity. However, BMI alone may not reliably indicate an MS pattern.