This part of an on-going intervention trial analyses impacts of obesity on psychosocial factors and health. The study sample comprised 800 obese men (BMI > or = 34 kg/m2) and 943 women (BMI > or = 38 kg/m2) ranging in age from 37 to 57 years. All participants completed standardized health-related quality of life measures, a validated obesity-specific eating inventory and study-specific questionnaires on current and past health status, use of medical care and medications, socioeconomic status, dietary habits, physical activity habits, weight history and familial history of obesity. Chronic patients and population samples were used as reference. The obese reported distinctly poorer current health and less positive mood states than the reference subjects, women being worse than men. Anxiety and/or depression on a level indicating psychiatric morbidity were more often seen in the obese and again women reported more affliction than men. Furthermore, the average poor mental well-being was worst than in chronically ill or injured patients, such as rheumatoid, cancer survivors and spinal cord injured persons. Predictors of perceived health and psychosocial functioning could be discerned using a comprehensive system of statistical analyses (16-28% explained variance). A background of both somatic and psychiatric morbidity was decisive for the health and psychosocial functioning in the obese; joint symptoms and angina pectoris dominated among somatic variables. Physical inactivity was the most prominent of traditional risk factors. The number of dieting attempts and body image were important weight correlates. Our results provide further evidence to the effect that severe obesity is a crippling condition.