To investigate the prevalence of multimorbidity and complex multimorbidity and their association with sociodemographic and health variables in individuals with severe obesity. This is a baseline data analysis of 150 individuals with severe obesity (body mass index ≥ 35.0 kg/m2) aged 18-65 years. The outcomes were multimorbidity and complex multimorbidity. Sociodemographic, lifestyle, anthropometric and self-perceived health data were collected. Poisson multiple regression was conducted to identify multimorbidity risk factors. The frequency of two or more morbidities was 90.7%, three or more morbidities was 76.7%, and complex multimorbidity was 72.0%. Living with four or more household residents was associated with ≥ 3 morbidities and complex multimorbidity. Fair and very poor self-perceived health was associated with ≥ 2 morbidities, ≥ 3 morbidities and complex multimorbidity. A higher BMI range (45.0-65.0 kg/m2) was associated with ≥ 2 morbidities and ≥ 3 morbidities. Anxiety (82.7%), varicose veins of lower limbs (58.7%), hypertension (56.0%) were the most frequent morbidities, as well as the pairs and triads including them. The prevalence of multimorbidity and complex multimorbidity in individuals with severe obesity was higher and the risk for multimorbidity and complex multimorbidity increased in individuals living in households of four or more residents, with fair or poor/very poor self-perceived health and with a higher BMI
