Obesity, as defined by the World Health Organization (WHO) as an abnormal or excessive accumulation of fat that presents a risk to health, has reached pandemic levels. Since 1980, its prevalence has doubled, affecting approximately one-third of the world's population. This increase spans all ages and both sexes, regardless of geographic location, ethnic origin, or socioeconomic level, though it is more prevalent in older individuals and women.
Obesity is a complex multifactorial disease primarily caused by an imbalance between energy intake and expenditure. Genetic, epigenetic, social, and microenvironmental factors contribute to its development. The main drivers of this pandemic are changes in the global food system, increased sedentary behavior, and reduced physical activity.
Complications and comorbidities associated with obesity include nearly all non-communicable diseases, such as type II diabetes, myocardial infarction, various types of cancer, immune system problems, and increased mortality in adulthood. Obesity also poses a significant economic cost, with 32% higher healthcare expenses compared to people of normal weight, divided into 31.8% direct costs and 68.2% indirect costs.
Currently, the most effective and cost-efficient long-term treatment for weight loss in people with obesity and comorbidities, or severe obesity, is bariatric surgery. Bariatric surgery is cost-effective, especially in the long term, helping to reduce body weight in the first years after the intervention (56.7% for gastric bypass and 45.9% for gastric balloon in the first ten years), improving metabolic control, and reducing obesity-related comorbidities.
However, individuals undergoing gastric bypass or gastric balloon surgery tend to regain weight in the long term. At least one in six operated individuals regain weight, and by 24 months post-surgery, up to 50% of patients regain weight. Factors such as genetics, anatomy, gastrointestinal hormones, adherence to a balanced diet, and healthy behaviors (reducing sedentary behavior and increasing physical activity) influence weight regain after bariatric surgery.
Sedentary behavior and physical activity are crucial for maintaining weight loss post-bariatric surgery. Physical activity post-surgery increases weight loss by 4%, and when performed before the intervention, improves weight loss at 12 months follow-up. However, the predisposition to obesity and weight regain post-surgery is influenced by factors such as lack of professional support, accessibility to sports facilities, and low socioeconomic status, making it difficult to improve physical activity levels and reduce sedentary behavior with simple health advice.
Despite this knowledge, hospital interventions before and after bariatric surgery focus on improving diet and only offer advice on physical activity, never physical activity and health behavior change interventions. Although diet is crucial and these interventions are often sufficient, physical activity and reducing sedentary behavior require supervised interventions of more than six months to achieve long-term behavior changes.
For these reasons, it is important to study through randomized clinical trials, with long-term follow-up, the effects of physical activity and reducing sedentary behavior on weight control, metabolic outcomes, and the quality of life, both mental and physical, of people with obesity who are going to undergo or have undergone bariatric surgery.
The B-FIT (Bariatric surgery and FITness) project aims to create a new referral and intervention model, from Hospital Sant Joan de Déu (Fundación Althaia) to the University of Vic-Central University of Catalonia, for physical activity and reducing sedentary behavior in people with obesity, both before and after bariatric surgery. This model aims to prevent post-surgery weight regain and promote healthy habits through behavior change techniques and supervised physical activity.
