Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia with a prevalence of 2% in general population. Incidence and prevalence of AF has been slightly increasing due to increasing age, improved ability to treat cardiac diseases, and higher incidence of obesity and other risk factors associated with AF. AF is associated with higher morbidity and mortality mainly caused by heart failure and stroke. Catheter ablation (with pulmonary vein isolation as a cornerstone) presents the most effective treatment method of AF. Recent observational studies have shown that intensive risk factor and lifestyle modifications, such as weight loss, reduced alcohol intake, and increased physical activity, are also associated with improved rhythm outocome. Head-to-head comparison of this very different methods has not been done yet. The aim of the project is to compare the effect of catheter ablation with lifestyle modification (risk factor modification) in a prospective, randomized, multicenter study on the maintenance of sinus rhythm (monitored using implantable ECG reveal), and on the progression of the fibrosis of the left ventricle.