Objective: To investigate the short-and medium-term (ie, at 1-y follow-up) effects of a hospital-based body weight reduction (BWR) program lasting 3 weeks in severely obese individuals. Design: Longitudinal, clinical intervention study entailing energy-restricted diet, tailored aerobic-strength exercise, psychological counselling and nutritional education during a 3-week period followed by 49 weeks of indirect supervision at home. Subjects: In all, 45 women and 19 men aged 30.277.2 y (mean7s.d.) with severe obesity (BMI: 41.374.3 kg/m 2 ), classified as weight losers (finaloinitial weight) and regainers (finalZinitial weight). Interventions: Body composition, physical performance and cardiovascular risk factors before and after the BWR program and at follow-up. Results: The large majority of the experimental subjects obtained a clinical success after the 1-y period, and the rate was higher in females (n ¼ 37/45, ie, 82.2%) than in males (n ¼ 11/19, ie, 57.9%). At follow-up, weight losers had higher percent fat-free mass, muscle strength, HDL-cholesterol and self-reported physical activity level and lower total cholesterol and glucose levels than weight regainers (Po0.05-0.01). Males displayed significantly larger fat-free mass losses than females at post-BWR and at follow-up. Conclusions: A 3-week hospital-based integrated BWR program resulted in a high rate of clinical success in severely obese individuals at 1-y follow-up (particularly in females), that was associated with increased levels of self-reported physical activity and improved muscle strength and lipid profile. Further research is needed to establish the long-term effects (ie, at 2-5 y) associated to this treatment.